Module, Powertrain Control (Pcm): Description
The Powertrain Control Module (PCM) is a digital computer containing a micro-controller. The PCM receives input signals from various switches and sensors referred to as PCM inputs. These inputs are as follows:
- Air conditioning pressure transducer
- Automatic Shutdown (ASD) / main relay
- Battery voltage
- Brake switch
- Camshaft Position (CMP) sensor
- Crankshaft Position (CKP) sensor
- Distance sensor (from transmission control module)
- Exhaust Gas Recirculation (EGR) position feedback (if equipped)
- Engine Coolant Temperature (ECT) sensor
- Heated oxygen sensors
- Ignition sense
- Inlet Air Temperature (IAT) sensor
- Knock sensor
- Manifold Absolute Pressure (MAP) sensor
- Park/Neutral (from trans range sensor)
- Power steering pressure switch
- Proportional purge sense
- Controller Area Network - Chassis (CAN-C) bus
- Speed control
- Transmission control relay (Switched B+)
- Transmission pressure switches
- Transmission temperature sensor
- Transmission Input Shaft Speed (ISS) sensor
- Transmission Output Shaft Speed (OSS) sensor
- Vehicle speed
Based on the above inputs, the PCM adjusts various engine and vehicle operations through devices referred to as PCM outputs. These outputs are as follows:
- Air conditioning clutch relay
- Data Link Connector (DLC) (CAN-C bus data)
- Double start override
- EGR solenoid (if equipped)
- Fuel injectors
- Generator field
- High speed fan relay
- Ignition coils
- Natural vacuum leak detection
- Low speed fan relay
- Manifold Tuning Valve (MTV) actuator
- Proportional purge solenoid
- Short Runner Valve (SRV)
- Speed control relay
- Speed control vent relay
- Speed control vacuum relay
- Torque reduction request
- Transmission control relay
- Transmission solenoids
- 5 volt output
Based on inputs it receives, the PCM adjusts fuel injector pulse width, idle speed, ignition timing, and canister purge operation and EGR, if equipped. The PCM regulates the cooling fans, air conditioning and speed control systems. The PCM changes generator charge rate by adjusting the generator field.
The PCM adjusts injector pulse width (air-fuel ratio) based on the following inputs.
- Manifold absolute pressure
- Engine speed (CKP sensor)
- Battery voltage
- IAT sensor
- Engine coolant temperature
- Exhaust gas oxygen content (heated oxygen sensors)
- Throttle position
The PCM adjusts engine idle speed through the idle air control motor based on the following inputs.
- Brake switch
- Engine coolant temperature
- Engine speed (CKP sensor)
- Park/Neutral
- Transaxle gear engagement
- Throttle position
- Vehicle speed (from Transmission Control Module (TCM)
The PCM adjusts ignition timing based on the following inputs.
- Inlet air temperature
- Engine coolant temperature
- Engine speed (CKP sensor)
- Knock sensor
- Manifold absolute pressure
- Park/Neutral (from trans range sensor)
- Transaxle gear engagement
- Throttle position
The camshaft and crankshaft signals are sent to the PCM. If the PCM does not receive both signals within approximately one second of engine cranking, it deactivates the fuel pump. When deactivated, power is shut off to the fuel injectors, ignition coils, fuel pump and the heating element in each oxygen sensor.
The PCM contains a voltage converter that changes battery voltage to a regulated 5 volts. The 5 volts power the camshaft position sensor, and crankshaft position sensor. The PCM also provides a regulated 5 volts supply for the manifold absolute pressure sensor, throttle position sensor and EGR (if equipped).
The PCM engine control strategy prevents reduced idle speeds until after the engine operates for 320 km (200 miles). If the PCM is replaced after 320 km (200 miles) of usage, update the mileage in new PCM. For PCM/ECM Reprogramming. Refer to MODULE PROGRAMMING .