Operation - Pcm

The PCM operates the fuel system. The PCM is a pre-programmed, triple microprocessor digital computer. It regulates ignition timing, air-fuel ratio, emission control devices, charging system, certain transmission features, speed control, air conditioning compressor clutch engagement and idle speed. The PCM can adapt its programming to meet changing operating conditions.

The PCM receives input signals from various switches and sensors. Based on these inputs, the PCM regulates various engine and vehicle operations through different system components. These components are referred to as Powertrain Control Module (PCM) Outputs. The sensors and switches that provide inputs to the PCM are considered Powertrain Control Module (PCM) Inputs.

The PCM adjusts ignition timing based upon inputs it receives from sensors that react to: engine rpm, manifold absolute pressure, engine coolant temperature, throttle position, transmission gear selection (automatic transmission), vehicle speed, power steering pump pressure, and the brake switch.

The PCM adjusts idle speed based on inputs it receives from sensors that react to: throttle position, vehicle speed, transmission gear selection, engine coolant temperature and from inputs it receives from the air conditioning clutch switch and brake switch.

Based on inputs that it receives, the PCM adjusts ignition coil dwell. The PCM also adjusts the generator charge rate through control of the generator field and provides speed control operation.

1. A/C request (if equipped with factory A/C)
2. A/C select (if equipped with factory A/C)
3. A/C pressure transducer
4. Auto shutdown (ASD) sense
5. Battery temperature
6. Battery voltage
7. Brake switch
8. J1850 bus (+) circuits
9. J1850 bus (-) circuits
10. Camshaft position sensor signal
11. Crankshaft position sensor
12. Data link connection for DRB scan tool
13. Engine coolant temperature sensor
14. Fuel level (through J1850 circuitry)
15. Generator (battery voltage) output
16. Ignition circuit sense (ignition switch in on/off/crank/run position)
17. Intake manifold air temperature sensor
18. Knock sensors (2 on 3.7L engine)
19. Leak detection pump (switch) sense (if equipped)
20. Manifold absolute pressure (MAP) sensor
21. Oil pressure
22. Oxygen sensors
23. Park/neutral switch (auto. trans. only)
24. Power ground
25. Power steering pressure switch
26. Sensor return
27. Signal ground
28. Speed control multiplexed single wire input
29. Throttle position sensor
30. Transfer case switch (4WD range position)
31. Vehicle speed sensor

1. A/C clutch relay
2. Auto shutdown (ASD) relay
3. J1850 bus (+/-) circuits for: speedometer, voltmeter, fuel gauge, oil pressure gauge/lamp, engine temp. gauge and speed control warn. lamp
4. Clutch pedal position switch override relay
5. Data link connection for DRB scan tool
6. EGR valve control solenoid (if equipped)
7. EVAP canister purge solenoid
8. Five volt sensor supply (primary)
9. Five volt sensor supply (secondary)
10. Fuel injectors
11. Fuel pump relay
12. Generator field driver (-)
13. Generator field driver (+)
14. Idle air control (IAC) motor
15. Ignition coil(s)
16. Leak detection pump (if equipped)
17. Malfunction indicator lamp (Check engine lamp). Driven through J1850 circuits.
18. Oxygen sensor heater relays
19. Oxygen sensors (pulse width modulated)
20. Radiator cooling fan relay (pulse width modulated)
21. Speed control vacuum solenoid
22. Speed control vent solenoid
23. Tachometer (if equipped). Driven through J1850 circuits.
24. Transmission convertor clutch circuit. Driven through J1850 circuits.