Powertrain Control Module
The Powertrain Control Module (PCM) is located in the engine compartment. See Fig 2. The PCM is a digital computer containing a microprocessor. The PCM receives input signals from various switches and sensors referred to as PCM inputs. Based on these inputs, the PCM adjusts various engine and vehicle operations through devices referred to as PCM outputs. See INPUT DEVICES and OUTPUT SIGNALS .
Based on inputs the PCM 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, A/C 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.
- Battery Voltage
- Inlet Air/Intake Air Temperature Sensor
- Engine Coolant Temperature
- Engine Speed (Crankshaft Position Sensor)
- Exhaust Gas Oxygen Content (Heated Oxygen Sensors)
- Manifold Absolute Pressure
- 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 (Crankshaft Position Sensor)
- Park/Neutral (Transmission Gear Selection)
- Transaxle Gear Engagement
- Throttle Position
- Vehicle Speed (From Transmission Control Module)
The PCM adjusts ignition timing based on the following inputs.
- Inlet Air Temperature
- Engine Coolant Temperature
- Engine Speed (Crankshaft Position Sensor)
- Knock Sensor
- Manifold Absolute Pressure
- Park/Neutral (Transmission Gear Selection)
- Transaxle Gear Engagement
- Throttle Position
The Automatic Shutdown (ASD) and fuel pump relays are mounted externally, but are turned on and off by the PCM. 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 ASD and fuel pump relays. When these relays are deactivated, power is shutoff to the fuel injectors, ignition coils, fuel pump and the heating element in each oxygen sensor.
The PCM engine control strategy prevents reduced idle speeds until after the engine operates for 200 miles. If the PCM is replaced after 200 miles of usage, the mileage must be updated in the new PCM. The PCM contains a self-diagnostic system which stores a Diagnostic Trouble Code (DTC) if an electronic control system failure exists. DTCs may be retrieved from PCM for system diagnosis by using a scan tool. For more information on self-diagnostic system, see SELF-DIAGNOSTIC SYSTEM .
On 2.4L, the PCM contains a voltage converter that changes battery voltage to a regulated 5.0 volts. The PCM provides a 5.0-volt supply for the manifold absolute pressure sensor, throttle position sensor, camshaft position sensor, crankshaft position sensor and EGR if equipped.
On 2.7L, the PCM contains a voltage converter that changes battery voltage to a regulated 8.0 volts. The 8.0 volts powers the camshaft position sensor and crankshaft position sensor. The PCM also provides a 5.0-volt supply for the manifold absolute pressure sensor, throttle position sensor and EGR if equipped.