Powertrain Control Module - Operation

OPERATION

The main function of the Powertrain Control Module (PCM) is to electrically control the fuel system. The PCM also controls the functions of transmission.

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 PCM Outputs. The sensors and switches that provide inputs to the PCM are considered PCM Inputs.

NOTE: PCM Inputs:

- Accelerator Pedal Position Sensor (APPS) Signals No. 1 and No. 2
- AC system pressure
- Auto shutdown (ASD) sense
- Battery voltage
- Brake switch
- Camshaft Position Sensor (CMP)
- Crankshaft Position Sensor (CKP)
- Data link connection for a scan tool
- EGR Air Flow Control
- EGR Valve
- Engine Coolant Temperature (ECT) sensor
- Exhaust Gas Temperature sensor
- EATX module (if equipped)
- Fuel level
- Fuel pressure sensor
- Fan speed (engine cooling fan)
- Generator (battery voltage) output
- Governor pressure (Auto. trans.)
- Ground circuits
- Inlet air temperature sensor/pressure sensor
- Intake air temperature sensor/MAP sensor
- CAN C BUS (+) circuits
- CAN C BUS (-) circuits
- Key switch (ignition)
- Oil Pressure switch
- Overdrive switch (automatic transmission only)
- Park/neutral switch (auto. trans. only)
- Power ground
- SCI datalink bus (+) circuits
- SCI datalink bus (-) circuits
- Sensor return
- Signal ground
- Speed control multiplexed single wire input
- Transfer case switch (4WD range position)
- Transmission governor psi (automatic transmission only)
- Transmission OSS (automatic transmission only)
- Transmission oil pressure (automatic transmission only)
- Transmission oil temperature (automatic transmission only)
- Transmission throttle valve position (automatic transmission only)
- Vehicle speed signal
- Water-In-Fuel (WIF) sensor

NOTE: PCM Outputs:

After inputs are received by the PCM, certain sensors, switches and components are controlled or regulated by the PCM. These are considered PCM Outputs. These outputs are for:

- A/C clutch relay
- Auto shutdown (ASD) relay
- Data link connection for diagnostic scan tool
- EGR air flow control
- EGR valve
- Fan clutch PWM
- Five volt sensor supply (primary)
- Five volt sensor supply (secondary)
- Fuel control actuator
- Fuel injector driver circuits
- Fuel transfer (lift) pump
- Generator field driver (-)
- Generator field driver (+)
- Governor pressure (VFS solenoid)
- Intake manifold air heater relays No. 1 and No. 2 control circuits
- CAN C BUS (+/-) circuits for: speedometer, voltmeter, fuel gauge, oil pressure gauge/lamp, engine temp. gauge and speed control warn. lamp
- Malfunction indicator lamp (Check engine lamp). Driven through J1850 circuits.
- Oil pressure switch/warning lamp (databus)
- Overdrive/3-4 shift solenoid (automatic transmission only)
- SC source
- SCI datalink bus (+) circuits
- SCI datalink bus (-) circuits
- Speed control vacuum solenoid
- Speed control vent solenoid
- Tachometer (if equipped). Driven through J1850 circuits.
- TCC solenoid (automatic transmission only)
- Transmission battery relay (automatic transmission only)
- Transmission throttle valve actuator (automatic transmission only)
- Transmission governor solenoid (automatic transmission only)
- Wait-to-start warning lamp (databus)
- Turbo wastegate solenoid
- Water-In-Fuel (WIF) warning lamp (databus)