Understanding ABS Module Logic

Understanding The Most Connected And Sophisticated Module On A Vehicle

The ABS controller/modulator is the heart of any ABS or ESC system. The modulator gets the brake pressure from the master cylinder and houses the valves and solenoids that control the pressures to the wheel. During normal operation, the pressure from the master cylinder goes through the hydraulic control unit (HCU) unaltered.

The anti-lock braking system computer or HCU is a node on a high-speed vehicle bus. This means the diagnostic information is accessed through the OBD-II DLC.

ABS is the foundation of the ESC system. ESC systems add software and sensors that measure yaw, steering angle and even control of the throttle to keep the vehicle under control. The ABS modulator also performs electronic brake distribution (EBD).


By my estimation in looking at service information, 40% of ABS codes are about communication with other modules on the series data bus and the data shared between the linked modules. Many of these codes have in the descriptions “loss of communication,” “data mismatch,” or other wording that indicates the information required is not present, or it is not plausible. The code might be specific to the network, indicating  communication loss with a steering angle sensor cluster, or it could indicate a complete loss of the total communication network.

Nearly 30% of codes concern the internal operation of the ABS module, including the pressure sensor(s), solenoids and pump. These codes can indicate open and shorts in the circuits. Also, they can indicate if a correction did not produce the expected change in hydraulic pressure.

Another 20% of the codes concern the wheel speed sensor operation. These can indicate problems with the circuits and plausibility or the data from the wheel speed sensors.

The remaining 10% of codes are manufacturer-specific or are unique to the system. They can also help diagnose EBD, ESC and traction control problems. 

These codes have monitors that typically run continuously and have self-checks running when the vehicle is started. Since ABS or stability control systems are critical to the safety of the vehicle, any problems detected will disable the ABS module. Looking up the code description and criteria should be one of the first steps in a diagnostic process. 

HCU Mechanical Problems

A basic ABS four-channel system will have eight solenoids (four isolation/four dump), or two for each wheel. Some systems will have more solenoids or valves to isolate the master cylinder from the HCU. ESC systems will typically have 12 or more.

Mechanical issues with the HCU are rare, but they can happen. Valve seats and pintles can become stuck or not seat properly due to debris, corrosion or contaminated brake fluid.

If the inlet/isolation valve is stuck open, it will not affect standard braking in any way. It will only hurt the ABS system. This could lead to a pulling condition during ABS activation.

If an outlet/dump valve is stuck open in one circuit, this could cause a pull condition during normal braking, due to the loss of brake pressure at a wheel. Typically, this is not discovered until brake hoses, calipers and other parts have been replaced.

Sometimes a stuck or defective solenoid or pump will set a code. A solenoid has a resistance between 2-8 ohms. On some units, it is impossible to access the individual solenoids. Testing the unit with a scan tool with bidirectional control might be the best way to confirm the condition of the HCU. 

Most vehicles equipped with ESC will have 12 valves or solenoids in the HCU. Eight solenoids control the wheels. Four additional solenoids can block off the master cylinder and allow the pump to send pressure to a specific wheel.

Understeer is a condition where the wheels are turned, but the vehicle continues to travel in a straight line. This is sometimes described as a push.

The ESC computer would see this event through the sensors. The wheel speed sensors in the front typically read slower than in the rear. The computer would also see that the steering angle is higher than the intended path. The ESC system needs to intervene before the event occurs, and it needs to anticipate the problem and correct as the vehicle travels.

This is what the ESC sees during an understeer event. The SAS angle is at +52º, meaning the customer has the wheel turned to the right at a significant angle. Even with the steering wheel turned, the yaw and accelerometer read like the vehicle is going straight. The APPS, or throttle pedal position sensor, shows the driver is off the gas and the brake pedal is not pressed.

The deciding information for the system is in the wheel speed sensor inputs. Between the front and rear, there is a 6 – 9 mph difference between the front and rear speeds. The front wheels are traveling slower than the rears.

 The diagnostic strategy with any ABS problem is to look at it as an engine drivability issue. Instead of adjusting the air/fuel mixture to achieve the best possible power and emission by monitoring oxygen and MAF sensors, the ABS system manages the hydraulic pressure at the wheels using even more sophisticated sensors that measure the dynamics of the vehicle.

Article courtesy Brake & Front End.


Kia Tech Tip: AWD System Hydraulic Actuator Replacement


2011-2016 Sportage
2011-2015 Sorento

This bulletin provides the procedure for replacement of the hydraulic actuator of some All-Wheel Drive (AWD)-equipped 2011-2016 Sportage trucks (produced from May 6, 2010-February 19, 2013) and some AWD-equipped 2011-2015 Sorento models (produced from October 24, 2009-December 11, 2014). 

The vehicles may exhibit an inoperative AWD system with the Malfunction Indicator Lamp (MIL) on and DTCs P1820/1821/1822/1823/1824. To correct this concern, replace the affected hydraulic actuator by referring to the applicable service procedure in the service information.

Do NOT Replace The Coupling Assembly For These Concerns:

• P1820 Pump for 4WD Motor High overcurrent detected
• P1821 Pump for 4WD Motor Wire Short to Battery
• P1822 Pump for 4WD Motor Wire Open Load
• P1823 Pump for 4WD Motor Wire Short to Ground
• P1824 Pump for 4WD Slow Thermal Overload

Service Procedure

Replace the affected hydraulic actuator with a new unit using the service information. To avoid fluid leaks, do not replace the actuator when coupling assembly is installed on the transfer case. Hold the coupling assembly upright when replacing the hydraulic actuator. 

Article courtesy Brake & Front End.


R-1234yf Safety Procedure Checklist

Remember that R-1234yf is only mildly flammable. To become flammable, the mixture of air and refrigerant in a closed area like a vehicle cabin would need to be between 6.5% and 12.3% of the chemical vapor. This mixture must then experience a significant amount of energy to ignite it. In some lab tests, a spark the equivalent of a direct short at the battery didn’t ignite it. But flammability is flammability, and precautions must be taken, both for you, the vehicle, your customers and the environment.

Below are the Specific Safety Procedures from the Mobile Air Conditioning Society’s Certification Training Manual.

If you missed our article all about R-1234yf and what it means for you, click here.

• Ensure good ventilation in the work area and do not allow the refrigerant to pool in or under the vehicle, or in any low area such as a stairwell or pit. Keep car doors and windows open when charging the A/C system to prevent an accumulation of refrigerant in case of a major refrigerant leak.

• Remove ALL sources of sparks, flame or high heat from the immediate work area. This may include non-A/C-related equipment such as grinders, welders, dryers and similar equipment. Move equipment with electric motors or switches that spark internally to a safer area. Remember also that a vehicle’s ignition system can produce external sparks under some conditions — take great care to prevent arcing and accidental grounding of electrical circuits.

• Use LED work lights to prevent the risk of a broken bulb in the work area.

• Do not smoke or permit smoking anywhere in or near the work area.

• Keep well-maintained fire extinguishers in the work area and know how to use them.

• Always wear personal protective equipment during service, particularly goggles with side panels and gloves (impermeable to refrigerant). Exposure of the skin to refrigerant may result in frostbite, in which case the affected area should be rubbed with lukewarm water.

• A physician shall be consulted immediately in the event of complaints following exposure to high refrigerant concentrations. Complaint symptoms may include: increased breathing rate, breathlessness, headache, accelerated pulse, dizziness.

• Do not store refrigerant tanks in low areas such as basements or stairwells and do not transport tanks without securing them.

• If the vehicle uses hybrid or all-electric propulsion, follow the correct procedure to deactivate the high voltage electrical system before beginning repairs.

• Prevent accidental release and exposure to refrigerant — only connect service equipment when high-side pressures have decreased, usually after the engine and compressor have been off for three minutes or more.

• Do not allow anyone under the vehicle while recharging the system. Unexpected refrigerant leakage or a sudden release of the pressure valve will pool refrigerant near the ground. Always maintain good ventilation in the work area.

• Each machine or device used to service a system with R-1234yf must be designed and approved for use with a flammable gas. Do not attempt to use equipment designed for other refrigerants on this system.

• Read the label on the vehicle and know the correct amount of refrigerant to return into the system after evacuation.

Article courtesy Underhood Service.


Maintenance Matters: Visibility Is The Top Safety Concern

It doesn’t matter how much emphasis you put on the condition of a vehicle’s components – if the driver can’t see what’s in front of him or her, safety will absolutely be compromised.

Wiper blades wipe off rain

The most important safety system in a vehicle is the driver’s vision and in the winter visibility is especially critical. 

Road salt, brine, ashes, beet juice – whatever  messy road treatments are used across the country get thrown onto the windshields and headlights, reducing light output and the driver’s ability to see down the road.

Windshield Washer Fluid

Windshield washer fluid solutions are more than just water and methyl alcohol or glycol, and they do more than just clean the windshield. Many solutions use detergents and solvents to remove ice and road spray from the windshield. 

Windshield washer fluid also protects the windshield and pump. The solution is formulated to act as a lubricant so the wipers will not scratch the coating on the glass. Plus, it helps to lubricate the pump in the reservoir and keep the electric motor cool. Proper windshield washer fluid also acts as an antibacterial agent to prevent bacteria and algae from growing in the reservoir.

There is a difference in seasonal wiper fluids – using a premium washer fluid is a good practice for your shop and excellent advice for your customers. Winter formulations are designed with higher alcohol contents to keep from freezing in solution under the hood, however remember that alcohol evaporates faster than water. In the winter this can mean that what’s left on the windshield is simply water with cleaning solvent, which can freeze at highway speeds.. 

Wiper Blades

Wiper blades are subjected to torture on a daily basis. Sun and exposure to ozone can cause them to lose the ability to keep the blade’s edge in contact with the windshield. Cold temperatures can compound the problem by making the blade stiff.    

A sure tool to measure the performance of a blade is a spray bottle filled with water. When a car is in for service, spray the windshield to see if the blades can remove the water without streaks or chatter.  

The main challenge for a winter wiper blade is snow and ice. On regular frame-style wiper blades, snow and ice can clog the frame and prevent the wiper from making even contact. Winter blades may use a rubber boot over the frame to prevent snow/ice buildup, and newer frameless-style wiper blades do not experience this problem.

If the blades are frozen to the windshield, it’ll be in your customers’ best interest to loosen them from the icy grip before using them. The rubber will last longer and the wiper motor will experience less stress.

Better Bulbs

Headlights aren’t what they used to be, and replacing them may not be a DIY operation. Many headlight replacement procedures today require the removal of the front fascia or bumper cover. Know your bulbs! 

Halogen Headlights: The halogen bulb is the type of headlight most drivers are familiar with, as it has been used in production since the 1960s. Characterized by its warm yellow glow, halogen bulbs are still popular with car manufacturers due to their low cost and reliable brightness. However, halogen bulbs simply don’t last as long as some other options and aren’t as bright.

HID Headlights: High-intensity discharge (HID) headlights, sometimes called Xenon, are brighter to enhance visibility and make peripheral objects such as street signs and pedestrians easier to see. The downside to the brighter output of HID headlights is that these bulbs can cause glare problems with oncoming drivers. These bulbs are also more expensive than their halogen counterparts; however, they do last longer to make up for some of the cost. 

LED Headlights: Light-emitting diode (LED) headlights have been available since the mid-2000s. They are smaller in stature than halogen and HID headlights and can easily fit where other products may not. They offer energy efficiency and brightness but are commonly the most expensive option on the market. 

Article courtesy ImportCar.


5 Tricks To Solving Belt Noise

Engineering a belt system is one of the most difficult jobs for OEMs. There are contact, frictional, centrifugal and peripheral forces that must be taken into account. If they get it right, the belt will be quiet, efficient and last 100,000 miles. If they get it wrong, the belt will be noisy or rob the engine of power. For technicians, the job is even tougher. Variables that the engineer did not factor in can put the belt and your diagnostic skills to the test. But there are four techniques you can use to solve belt noise problems.

1. Remove the Belt

If you have a hard-to-isolate accessory drive belt noise, try removing the belt and running the engine. If the noise is still present after the belt is removed, it might be an issue with the motor mounts or the timing chain/belt. With the belt off, it is also a great chance to examine the pulleys and belt for potential problems like worn bearings inside the idler pulleys.

2. Tensioner Twist

Place a wrench on the tensioner and move the arm its entire range of motion at least three times. Feel for spring tension along with a fluid motion throughout. Any sticking or notching movement may indicate a problem with the spring or pivot bearing. The arm should move up and down. Any lateral movement could indicate a bad bearing or spring. Inside some belt tensioners, unseen to most technicians, is a dampening mechanism that absorbs shock. Excessive chattering or tensioner arm movement is not only the result of weak spring tension but also a worn dampener. This makes the tensioner a wear part with a limited life span.

3. Spray it Down

In the 1950s, the sales trick to sell a new belt was to spray a running belt to show that it was slipping or that the noise went away when wet. This trick went away when serpentine belts became more popular. But, this test can be used to isolate worn pulley bearings by eliminating belt noise that could be caused by an alignment problem. Use only water; old-school belt dressing will damage modern EPDM belts and cause more noise.

4. Get in the Groove

Like a tire, the friction between the belt and pulleys wears away at the belt, usually on the tops and walls of the ribs. Eventually, the grooves of the pulleys will bottom out on the grooves of the belt, and then the belt will start to slip.According to one belt supplier, as little as 5% of rib material loss and surface wear can affect how the belt performs, and just 10% belt slippage can affect the overall drivability of a vehicle. Belt manufacturers have simple gauges that can measure groove depth, overall thickness and cracks to quantify wear.

5. Check the Alignment

Pulley alignment tools can help you rule out alignment issues. They can give you the peace of mind that there is a pulley that is out of alignment. It is also a great tool to have if you do a lot of power steering pump or A/C compressor replacement jobs.  

Article courtesy Underhood Service.


Installing Subaru Stretch Belts

If you see a belt on a late-model Subaru does not have an automatic tensioner and runs between only two or three components, it’s probably a stretch belt. You may also notice some belts will have the words “stretchy” or “stretch” written on the back. These types of belts typically are used to turn the A/C compressor on the 2.5L four-cylinder engine in 2008 and up models.

The stretch belt can help to simplify the serpentine belt system on the Boxer engine. It can also increase the efficiency of the engine by allowing it to run with less tension on the alternator and power steering. Beyond that, it can extend the life of the alternator by reducing the load on the bearings.

Subaru stretch belts can last 100,000 miles or more. On a worn belt, the cracks or damage to the backing of the belt will not be evident to the naked eye. This is why an inspection method measuring groove depth is recommended — you simply cannot go by mileage recommendations alone.


When inspecting a stretch belt, always measure the depths of the groove with an inspection tool because the differences between a worn belt and a good belt can’t be seen or felt. The new materials used to manufacture a stretch belt will not crack or separate like older belts before the grooves are worn. Belt inspection gauges are available from manufacturers and distributors, so check their websites or ask your distributor if you’re in need.

Poor pulley alignment is the No. 1 cause of belt noise and premature wear of stretch belts. If the pulleys have poor alignment, the belt will be worn on the edges and might look frayed.

Alignment problems can stem from issues with shaft endplay in an A/C compressor or crankshaft. Alignment problems can also indicate a worn A/C clutch or a crankshaft pulley/dampener that is about to fail. Also note that leaking seals can contaminate the belt.

Worn Belts

When a stretch belt exceeds wear specifications, it’s no longer able to effectively grip the pulleys and will start slipping. The primary cause of this slippage is when material is removed from the belt’s grooves, rather than it stretching and losing tension.

Over time, small debris and the interaction with the pulleys will wear the shoulders and valleys of the grooves. When the grooves become too shallow, the pulleys bottom out. When this happens, the walls of the groove can no longer grip the pulley and it slips.

If you are removing an old stretch belt from a Subaru, just cut it. Even if the belt is still in excellent shape, the act of pulling the belt over the A/C compressor clutch or crankshaft pulley will damage the inner core.

These belts have a thermo-elastic core designed to keep tension on the pulleys during a long lifecycle. The material acts like shrink tubing for a wiring harness. Once the belt has been run and exposed to the underhood temperature, the heat will decrease the length of the belt and, therefore, properly tension it.

Never use a screwdriver or other sharp object to install the belt because if the belt is cut or the surface or grooves of the pulleys are damaged, the belt will eventually fail. Special tools are available from various tool and belt manufacturers that act as a ramp on the leading edge of the pulley. Some applications will require special tools to hold the belt on the accessory pulley, as is the case for the Subaru A/C compressor pulley.

There are many tool designs, but they all perform the same task of pulling the belt over the leading edge of the crankshaft pulley without damaging the belt. Always follow the directions for proper tool placement and for the correct direction to turn the crankshaft. After the belt is installed, confirm the belt is in the grooves and recheck there are no alignment problems. Run the engine for a few seconds before doing this final check.  

Article courtesy Underhood Service.


Scoping Ignition Waveforms

The grandfather of all waveforms is the secondary ignition waveform. Technicians have been looking at this waveform since the 1960s to determine the health of ignition system components. The secret to being able to capture and analyze secondary ignition waveforms is understanding what is happening in the coil and at the spark plug and how the scope measures and graphs the voltages and ignition event.Advertisement

How Is It Measured?

Measuring the voltage of the secondary ignition directly is not an option – these high voltages will damage any scope or meter. Capturing a secondary ignition waveform requires a capacitive probe. This type of probe can be either the traditional clamp over an ignition wire or a “paddle” that makes contact with the surface of the coil or wire. 

The primary and secondary windings of the coil transform the energy from low-voltage/high-current energy to high-voltage/low current energy. Eventually this energy is discharged through the spark plug electrodes. The flow of energy changes the magnetic field in the wires or coil and this change in the field is picked up in millivolts by the clamp or paddle probe. 

Most clamp or paddle probes have a conversion factor of 10:1. This means one volt at the scope input equals 1,000 volts or one kilovolt (kV) in the secondary. Some clamps or probes may have an attenuator (10:1 or 20:1), so make sure you read the instructions to properly set up your scope. Some scopes will convert the voltage scale to kV when the ignition probe is selected.

A capacitive probe should include a ground clamp as part of the test leads. This creates an easier path to ground for the thousands of volts generated by the coil. If the probe or clamp is not grounded, the voltage could damage the internal circuitry of the scope. Most scopes have a limit around 200 volts, and most ignition systems can generate more than 4,000 volts.

What Are The Settings For The Scope?

When you are trying to set up a scope to measure secondary ignition waveforms, the goal is to capture the ignition event from when power is applied to the coil to the point where the coil oscillates with the remaining energy. This can happen in 6-10 milliseconds. One millisecond per division is typically the optimal time base depending on the size of your screen and the type of ignition system.

A healthy coil and ignition system generates 5-7 kV at idle. As load and engine speed increase, the kV spike will increase. Some systems can generate more than 50 kV under certain conditions. You may need to adjust your voltage scales to capture the total output of the spike. Don’t get caught up on the height of the spike. Automakers are actively controlling the output of the coil to improve the longevity of the ignition components.

On most scopes, the trigger should be set to auto or single with an increasing slope. With some scopes, you will be able to use an auto or repeat trigger setting to stabilize the waveform. There are also options to offset or delay the trigger to fit the entire event on one screen.  

Try to become familiar with setting up secondary ignition triggers within your system before you are under the diagnostic labor gun. If you have a more advanced scope, you can select the secondary ignition probe in the probes menu – the presets will load the correct voltage range, time base and type of trigger. Some scopes will also convert the voltage scale to kV. Depending on the type of ignition system, you may have to fine tune the trigger and voltage scale to fully capture the waveform on a single screen. 

What Are The Sections Of The Waveform?

A secondary ignition waveform can be broken down into three parts. First, the area of the waveform shows dwell where the secondary of the coil is saturated with energy from the primary. Second, the spike shows the initial start of the spark between the electrodes. Third, the burn time is the area of the wave where the spark is burning between the electrodes and eventually stops.

Interpreting Secondary Ignition WaveForms

On modern coil over plug (COP), wasted spark or coil near plug systems you are using the secondary waveform as a comparative tool to compare the cylinders. You can compare a waveform to a known good pattern from a database or you can compare the waveform to the other cylinders. Waveforms will differ from engine to engine. 

On some systems, you may see a 1- to 2-kV hump after the spike, or you might not see a coil oscillation when the primary coil is energized.  This could be normal for some systems and abnormal for others. 

The secret is to compare the waveform with the other actual cylinders. Don’t get hung up on “this guy said this” or “that book says that.” In some cases, you could go down a diagnostic black hole.

Article courtesy Underhood Service.


Toyota FJ Cruiser Water Pump Replacement

Toyota’s original Land Cruiser was the company’s version of a Jeep that could go anywhere. In its time it was highly rated and collected, which led the Japanese juggernaut to bring back an updated SUV in 2007 called the FJ Cruiser. The retro-styled vehicle was again a go anywhere machine powered by a 4.0L V6 (1GR-FE) used in the Tacoma. The engines are durable and considered relatively robust for the time.

The early versions from 2007-’09 employed VVT-i on the intake cam and produced 236 hp on 87 octane, and 240 hp on 91 octane. An updated version of this engine uses Dual VVT-i, increasing the power to 270 hp on 87 octane and 285 hp on 91 octane.

For increased cooling efficiency, the 1GR employs four water passages, with two between the bores on each bank. The extra cooling reduces cylinder hot-spotting and keeps combustion chamber temperatures more uniform. While generally reliable, the 1GR has a lot of belt-driven accessories from the fan-clutch to the AC condenser and, of course, the water pump.

Replacing the water pump on the FJ Cruiser is a reasonably big job because of the number of components you have to remove to get to it, but it is relatively straight forward after that. The pump itself is a large cast aluminum piece with 17 bolts holding it on the front of the engine. The fan clutch is connected to the water pump pulley and is driven off the crankshaft pulley, which also operates the compressor and alternator as well as the power steering pump. The fan shroud must come off along with the fan clutch and serpentine belt.

Coolant leaks on the 1GR-FE commonly stem from corrosion and debris running through the bearing and surfaces of the water pump. If there are heavy coolant deposits on the water pump and surrounding areas, the pump should be replaced once the leak is verified. Technicians must be sure the leaks are not from other components on the front of the engine. The plastic thermostat housing uses an O-ring to seal it against the body of the water bypass housing. Check to make sure the leak is not coming from the plastic housing and that the O-ring is not flattened in any area.

Toyota recommends the paper towel test if you see dried coolant on the water pump. Wipe a dry paper towel on the area around the weep hole to determine if the leak is new or a result of debris being cleared when it was installed. If the paper towel remnants remain dry, there’s no need for replacement. But if the paper towel becomes damp/stained, you should replace the pump. Once you’re sure the cause of the leak is coming from the water pump, then you can continue the process of removing the accessories and pump.

It’s about a 2.5-hour job to replace the water pump and accessories such as the serpentine belt, and any worn or noisy idlers. Removing the skid plate isn’t necessary if you’re working from the top, but for access to some components from underneath, it may be a better option. Many of these vehicles have lift kits installed that can make it difficult to work from up top (e.g., this author uses a step stool to reach all of the components from the top of his lifted FJ).

On a side note, if you’re replacing the timing chain or have the front cover off, it’s a good idea to replace the water pump as well on a high mileage engine to be on the safe side. Free play in the pump bearing may indicate that the seal won’t hold for much longer and you’ll have to replace it soon anyway.

The engine cover should be removed to gain access from the top. Next, remove the fan shroud along with the fan and clutch and pull them out together. Once these are out of the way, you can tackle the drive belt. While turning the belt tensioner counterclockwise, you can align the holes in the assembly to insert a 6mm punch or bar so that it will hold the belt tensioner in position while the V-ribbed belt is removed.

The idler pulleys need to be removed along with the tensioner pulley to get access to all the water pump bolts. Note that the tensioner bolt is a reverse thread. The water bypass housing can be removed or loosened to slide the water pump out. There’s an O-ring on the top that mates between the housing and the pump. If you remove the bypass housing, most replacement kits contain new O-rings, so be sure to install them.

Keep track of the 17-bolts that line the water pump since there are two different sizes. The longer bolts thread through the water bypass housing and into the block. The shorter bolts run directly into the block. Torque the longer bolts to 81 in-lbs and the short ones to 17 ft-lbs.

The gasket for the water pump is layered steel with a rubberized coating. Use caution when sliding the gasket and pump into position so that it all stays in place when you bolt it all down. The gasket can be put on dry, but some people add a little high-temp silicone to the bolt threads to ensure a good seal.

Once the pump is replaced and the accessories belt is installed, fill the system and bleed the air out, then check for leaks. It’s not a difficult job but there’s a good number of parts to remove and keep track of, so it’s best to make room to lay it all out so you can find the parts easily. While the FJ Cruiser was discontinued in 2014, there are many still on the road today and many more Toyota models with the 1GR-FE engine.


Fuel Pump Diagnostics: Using Scan Tools

The most common diagnostic procedures for fuel pumps in the past were analog and hands on. Most fuel pump-related problems could be solved with a pressure gauge and voltmeter. Today, the scan tool is the most important tool when diagnosing a fuel supply problem.

On early vehicles, the fuel pump was energized when the key was turned on and a vacuum-operated diaphragm regulated fuel pressure. Today, input from at least two modules and various sensors that are networked on a high-speed serial data bus is required for a fuel pump to operate. While this may sound like it would complicate the diagnostic process, it actually simplifies diagnostics and can save you from unnecessarily dropping a fuel tank.

With a scan tool, it’s possible to verify if the modules controlling the fuel pump are receiving the correct data like oil pressure, crank position and key ­position. Some late-model imports have even turned the fuel pump into its own module or node on the high-speed serial data bus. The module may share data like the fuel level and tank pressure with the ­instrument cluster module and the ECM.

What this also means is that this data can be monitored with a scan tool. If the serial data bus is unable to communicate with certain modules like the theft deterrent system or even the Body ­Control Module (BCM), it could cause the fuel pump to shut down.

Most late-model vehicles have return-less fuel systems. Instead of using engine vacuum to a pressure regulator under the hood, the system uses engine data and varies the speed of the pump to meet fuel requirements. The pump is energized with pulse-width modulated voltage. This means that if you connect your voltmeter to the fuel pump circuit, the readings will bounce around instead of being a constant voltage.

A scope is required to graph the amperage and voltage. These systems have different modes for start, acceleration, deceleration and fuel cut off. On some vehicles, these modes can be observed on an enhanced or factory scan tool as part of the Mode 6 Data.

Initial Diagnostics

The most common ­customer complaints when it comes to fuel pumps are a no-start condition, intermittent no-start condition or even hard starting. The first step in any diagnostic process is to perform a ­visual inspection of the ­vehicle.

Next, verify the customer’s complaint. Many diagnoses go wrong because the technician fails to verify the customer’s concern. If the customer says it does not run, make sure it will not start and run.

Forget your “noid” lights on most modern vehicles. This low-cost tool worked well on simple vehicles, but with modern vehicles it can lead you down a diagnostic black hole. If the vehicle has Gasoline Direct Injection (GDI), there is no way you could even access the injectors to install a noid light. If you do feel compelled to prove the injectors are pulsing, try using a scope.

Forget the fuel pressure gauge at this point in the diagnostic process. Even if there is pressure at the fuel rail, this information is of little use on newer ­vehicles without having access to the parameters. Some port fuel injection systems and all GDI systems have pressure sensors that can be observed with a scan tool. Also, GDI-equipped Asian and ­European models do not have ports to attach the gauge.

After the visual inspection and verifying the customer’s complaint, it’s time to connect the scan tool. First, pull the codes and make sure the modules are communicating on their communication buses. Some low-end generic tools may not be able to talk to all the modules. This is where an enhanced or factory scan tool comes into its own.

Many enhanced or factory scan tools can perform a “health check” that can pull codes and parameters from the modules on the vehicle with just one press or click. Some scan tools have automated tests that can bi-directionally control components to automatically confirm operation.

With the codes pulled, you can come up with a ­diagnostic strategies and further tests to resolve the no-start condition. Service information is just as ­critical of a tool as a pressure gauge.

Every fuel system has a set of parameters that must be set in order for the pump to be energized. For some systems, this may include a crank sensor signal, oil pressure and maybe a check with the ­vehicle theft deterrent module.

If the vehicle has any “loss of communication” codes like U1000, resolve those problems first before diagnosing or replacing the fuel pump. While these codes may seem like they have nothing to do with the fuel pump, often a dead module or short in the serial bus can result in a no-start condition.

After you’ve performed the checks with your scan tool and have confirmed with the service information that it could be the fuel pump causing the no-start condition, you can carry out the physical tests to confirm the condition of the fuel pump.

GDI Strategies and Scan Tools

Diagnostics fundamentals for GDI are not that much different than conventional fuel injection systems. These systems inject the right amount of fuel directly into the cylinder. These systems are very efficient and are able to get the right amount of fuel into the cylinder so no fuel is wasted by not having to spray on the back of the intake valve.

In fact, after working on a few GDI systems, you may find that they get easier to work on due to the tighter long-term and short-term fuel trim parameters.

GDI makes more horsepower for a given engine size. This is why Mercedes-Benz and BMW have been able to get away from V10 and V12 engines. Utilizing GDI systems, their new V8s are able to make more power while using less fuel.

The diagnostic strategies are similar to port fuel systems, but most of these systems have an additional fuel pump, pressure sensors and a different style of injector.

With the injector in the combustion chamber, the pintle and seat of the fuel injector are under extreme pressures. To overcome the cylinder pressures, the fuel pressure supplier to the injector may be as high as 2,000 psi.

The in-tank pump in GDI systems is more responsible for volume than pressure. Fuel on this side of the system is called the low-pressure side. A fuel pump on the engine pressurizes the fuel for high-pressure injectors. This pump is driven off a lobe on the camshaft. This part of the fuel system is called the high-pressure side.

The pressure from the high-pressure fuel pump is monitored by the Powertrain Control Module (PCM) through a sensor and can be modulated by changing the volume of fuel entering the pump inlet. While specific pressures vary among different vehicle applications, most high-pressure pumps are capable of producing at least 2,000 psi of fuel pressure. These extremely high fuel pressure levels are required to overcome compression and combustion pressures ­inside the cylinder and to inject a relatively large volume of fuel directly into the cylinder in a very short amount of time.

Factory and enhanced scan tools can monitor pressure transducers on the high and low sides of the system. This information can be used to diagnose the health of the low-side and high-side pumps. These tools will have the PID parameters for these components as part of the Mode 6 data. These parameters can tell you what the pressures should be during the different modes of operation. Also, if this data is used in conjunction with the waveforms of the injector pulses, it’s possible to ­perform cylinder balance and other diagnostic tests. The pressure transducers can also be used to monitor system pressures to diagnose hard-start ­problems.

Maintenance and the reduced frequency of ­engine oil changes have been known to take their toll on some GDI high-pressure pumps. For example, some VWs and Audis are experiencing wear on the follower on the pump due to poor lubrication and oil that has broken down. The follower that rides on the camshaft can wear and lose metal at the base.

The pump is very sensitive to the changes in ­dimensions of the follower and it can result in lower fuel pressures. This condition is initially diagnosed with a scan tool and not feeler gauges.

So much of the diagnostic process for fuel pumps can be performed from the driver’s seat of the vehicle with a scan tool. This makes you a more productive technician and the ­diagnosis more accurate. And this translates into a more profitable shop.

Article courtesy Underhood Service.


Ford Transit Alignment Spec

Models: 2015 – Current

In 2015, Ford replaced the Econoline with a van that was designed for both Europe and North America called the Transit. This van is designed for fleets who will put on a lot of miles in a short amount of time. The Transit comes in 150, 250 and 350 sub-models. There is also a model with a dually rear axle. The alignment for this vehicle is simple with the only built-in adjustment being front toe. But, the camber and caster angles can be used to diagnose other problems.

Top Tips

Perform a complete inspection before the alignment to look for damage.

Since most Transits are used for hauling cargo and tools, keep this in mind if you are trying to solve an alignment or tire issue. An overloaded Transit will have significant changes to the ride height and front alignment angles.

The Transit is a platform with multiple variations for the van, bus and even roof height. When you are looking for the correct specifications, make sure you have the right model and even powertrain. Even the electric version has different front camber and caster specifications.

Front Suspension

The front suspension of the Transit uses struts. There is no practical way to adjust the camber. In the service information, they recommend shifting the front subframe. The procedure requires loosening four bolts that secure the subframe. These bolts are torque-to-yield and will require replacement.

Always look at the cross-camber measurements before trying to shift the subframe. If you are trying to reduce the camber on one side, you will be adding that camber to the other side. If the camber or even caster is off on just one side, look at the control arms and strut rod for damage. Also, look at the ride height. If one side is lower, it can change the camber.

Rear Suspension

The rear suspension uses a live axle with leaf springs. No adjustment is possible, but measuring the thrust angle and setback should be performed. To measure the rear ride height, measure the distance between the jounce bumper and the striker cup. If you see “helper” springs, ask the owner if he has had any issues with sagging in the rear. If the owner regularly overloads his van, it can impact the life of the wheel bearings.

After The Alignment

The Transit can be ordered with an optional lane-keeping system that alerts the driver if he drifts out of his lane. Some models have a steering wheel shaker that alerts the driver. If the camera is disturbed from its mount behind the windshield, it will need to be calibrated. The Steering Angle Sensor Module (SASM) is self-calibrating. But, if significant repairs were performed to the steering column or ABS system, there is a calibration protocol that will require a scan tool.

Article courtesy Brake & Front End.