Powertrain Control Module - Operation
OPERATION
The Powertrain Control Module (PCM) receives input signals from various switches and sensors. Based on inputs it receives, the PCM adjusts and controls fuel injector pulse width, idle speed, ignition spark advance, ignition coil dwell, EVAP canister purge, cooling fan, and air conditioning.
If the PCM does not receive the crankshaft position signal within approximately one second of engine cranking, it deactivates the ASD relays and fuel pump relay. When these relays deactivate, power is shut off to the fuel injectors, ignition coils, heating element in the upstream oxygen sensors, fan control relays and the fuel pump. The two Auto Shutdown (ASD) relays and fuel pump relay are mounted externally, but turned on and off by the PCM.
PCM SENSOR INPUTS
- A/C Request Signal
- Air Conditioning Controls
- Alternator Voltage Signal
- ASD1 Relay
- ASD2 Relay
- Battery Temperature
- Battery voltage
- Brake Switch Inputs
- Camshaft Position Sensor
- Crankshaft Position Sensor
- Engine Coolant Temperature Sensor
- Ignition Switch
- Dual Intake Air Temperature Sensors
- CAN-C
- Leak Detection Pump Switch
- Manifold Absolute Pressure (MAP) Sensor
- 2 Mass Airflow (MAF) Sensors
- 2 Knock Sensors
- Oil Pressure Sensor
- Oil Temperature Transducer
- Oxygen Sensors
- 2 Pedal Position Sensors
- Starter Signal
- 4 Throttle Position Sensors (2 in Each Throttle Body)
- Vehicle Speed Sensor
ENGINE IDLE SPEED
The PCM adjusts engine idle speed through the electronic throttle bodies based on the following inputs:
- Air Conditioning Signal
- Battery Voltage
- Coolant Temperature
- Engine Speed (Crankshaft Position Sensor)
- Engine Run Time
- Manifold Absolute Pressure
- Mass Airflow Sensor
- Throttle position
- Vehicle distance (Speed)
FUEL INJECTOR PULSE WIDTH
The PCM adjusts fuel injector pulse width (air-fuel ratio) based on the following inputs:
- Battery Voltage
- Coolant Temperature
- Intake Air Temperature
- Exhaust Gas Content (Oxygen Sensor)
- Engine Speed (Crankshaft Position Sensor)
- Manifold Absolute Pressure
- Mass Airflow Sensor
- Throttle Position
IGNITION TIMING
The PCM adjusts ignition timing based on the following inputs:
- Coolant Temperature
- Intake Air Temperature
- Engine Speed (Crankshaft Position Sensor)
- Manifold Absolute Pressure
- Mass Airflow Sensor
- Throttle Position
PCM SENSOR OUTPUTS
- Air Conditioning Clutch Relay
- Alternator Field Control
- Auto Shutdown (ASD) Relay
- CAN-C
- Data Link Connector
- Dual Electronic Throttle Bodies
- Duty Cycle EVAP Canister Purge Solenoid
- Four O2 Heater Control Outputs
- Fuel Injectors
- Fuel Pump Relay
- Ignition Coils
- LDP Solenoid
- Reverse Gear Lockout Solenoid
- Two Fan Relays
- VVT Solenoid
- 2nd/ 3rd Gear Lockout Solenoid
5 VOLT SUPPLY
There are two 5 volt circuits in this vehicle. A primary and a secondary.
PRIMARY CIRCUITS
- Crankshaft Position Sensor
- Electronic Throttle Control 1
- Manifold Absolute Pressure Sensor
- Pedal Position Sensor 1
SECONDARY CIRCUITS
- Camshaft Position Sensor
- Electronic Throttle Control 2
- Oil Pressure Sensor
- Pedal Position Sensor 2
IGNITION SIGNAL
The ignition sense input informs the Powertrain Control Module (PCM) that the ignition switch is in the off, on or run position.
PCM GROUND
Grounds are provided through multiple pins of the PCM connector. The vehicle uses five power ground and 14 separate sensor grounds.
The power grounds are used to control the ground side relays, solenoids, ignition coils or injectors. The signal grounds are used for any input that uses sensor return for ground.
The PCM case is shielded to prevent RFI and EMI. The PCM case is grounded.
Internally all grounds are connected together, however there is noise suppression on the sensor grounds.