The Powertrain Control Module (PCM) is often misdiagnosed for a variety of starting and driveability problems because it’s the part of the engine management system people understand the least. Actually, PCMs are fairly reliable, and if the engine cranks but still won’t start, the fault is usually something else that prevents the engine from getting fuel or spark.
The following text contains incomplete statements regarding powertrain control modules. Students should use the key words from the bottom of this page to complete the following commentary.
Note: Some words may be used more than once, some not at all.
The PCM uses input data from the oxygen sensor in the exhaust, as well as throttle ____1______, engine speed, load or airflow to control the injectors.
If a sensor circuit is malfunctioning and providing the PCM “bad” ____2_____, it can alter the output commands to the ignition coil(s), fuel injectors and _____3_______ controls.
When working with the fuel system, a PCM monitors signals from the engine management system sensors, processes the data and controls the ground path to pulse the fuel _____5______.
Closed loop control means the system is “self-regulating” and the PCM is controlling the injectors based on operating conditions, rather than preprogrammed (fixed) ____7______.
If an engine ____8_____ but won’t start because it is not getting any fuel, the PCM may not be energizing the fuel pump ___9_____, or it may be shutting off the relay after a certain period of time because it is not seeing a/an ____10____ signal from the engine.
On some engines, the PCM needs a signal from the ____11_____ position sensor to figure out where cylinder number one is so it can synchronize ___12______ timing in the proper firing order and/or the pulsing of sequential fuel injectors.
If a PCM is not working correctly because of an physical fault in its processor, ___13______ or circuit board, a ____14____ won’t fix the unit.
PCM reflashes are only used to update the operating ____15______ that customize the PCM allowing the vehicle to operate as designed – not the read-only basic computer operating instructions.
Key Words Selection
signals memory reflash programmed emission crankshaft injectors cranks instructions feedback RPM instructions energizing ignition relay camshaft position
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Pop Quiz Solution
The Powertrain Control Module (PCM) is often blamed for a variety of starting and driveability problems because that’s the part people understand the least. Actually, PCMs are fairly reliable, and if the engine won’t start, the fault is usually something else that prevents the engine from getting fuel or spark.
The following text contains incomplete statements regarding PCM units. Students should use the key words from the bottom of this page to complete the following commentary.
Note: Some words may be used more than one, some not at all.
The PCM uses inputs from the oxygen sensor in the exhaust, as well as throttle position, engine speed, load and airflow to control the injectors.
If a sensor is misbehaving and is feeding the PCM bad data, it can affect the output commands from the PCM to the ignition system, fuel system and emission controls.
When working with the fuel system, a PCM receives signals from all the fuel systems sensors, processes the data and transmits programmed electrical pulses to the fuel injectors.
Electronic feedback means the system is self-regulating and the PCM is controlling the injectors based on operating conditions, rather than preprogrammed instructions.
If an engine cranks but won’t start because it is not getting any fuel, the PCM may not be energizing the fuel pump relay, or it may be shutting off the relay after a certain period of time because it is not seeing an RPM signal from the engine.
On some engines, the PCM needs a signal from the camshaft position sensor to figure out where cylinder number one is so it can sync ignition timing in the proper firing order and/or the pulsing of sequential fuel injectors.
If a PCM is not working correctly because of an internal electronic fault in its processor, memory or circuit board, a reflash won’t fix the unit.
PCM reflashes are only used to update the operating instructions that tell the PCM what to do.
signals memory reflash programmed emission crankshaft injectors cranks instructions feedback RPM energizing ignition relay
camshaft position
Solution:
1 position
2 data
3 emissions
4 programmed
5 injectors
6 feedback
7 instructions
8 cranks
9 relay
10 RPM
11 camshaft
12 ignition
13 memory
14 reflash
15 instructions
