Operation

POWERTRAIN CONTROL MODULE (PCM)

The Powertrain Control Module (PCM) operates the fuel system. The PCM was formerly referred to as the SBEC or engine controller. The PCM is a pre-programmed, digital computer It regulates ignition timing, air-fuel ratio, emission control devices, charging system, speed control (if equipped), 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 PCM Outputs. The sensors and switches that provide inputs to the PCM are considered 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 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.


NOTE: Powertrain Control Module (PCM) In puts:


- A/C request (if equipped with factory A/C)

- A/C select (if equipped with factory A/C)

- Auto shutdown (ASD) sense

- Battery temperature

- Battery voltage

- Brake switch

- Camshaft position sensor signal

- Crankshaft position sensor

- Engine coolant temperature sensor

- Fuel level

- Ignition circuit sense (ignition switch in run position)

- Intake manifold air temperature sensor

- Manifold Absolute Pressure (MAP) sensor

- Oxygen sensors

- Oil pressure

- Park/neutral switch (auto. trans. only)

- Power ground

- SCI receive (DRB scan tool 16-way connection)

- Sensor return

- Signal ground

- Throttle position sensor

- Vehicle speed sensor


NOTE: Powertrain Control Module (PCM) Outputs:


- A/C clutch relay

- Auto Shutdown (ASD) relay

- CCD bus (+) circuits

- CCD bus (-) circuits

- Duty cycle EVAP canister purge solenoid

- Fuel injectors

- Fuel pump relay

- Generator field driver (-)

- Generator field source (+)

- Idle Air Control (IAC) motor

- Ignition coil

- SCI transmit (DRB scan tool 16-way connection)

- Transmission convertor clutch solenoid

The PCM contains a voltage convertor. This converts battery voltage to a regulated 5.0 volts.