On-Board Diagnostic System

PCM SYSTEM
The computerized engine control system is built around a Powertrain Control Module (PCM). The PCM monitors up to 22 inputs and responds with appropriate outputs to manage fuel delivery, ignition timing, and emission control devices, charging system, speed control and idle speed.

NOTE: The PCM can detect certain faults in its systems, the following is a list of the types of faults the PCM can detect.

MONITORED CIRCUITS
Open or Shorted Circuit - The PCM can determine if the input signal from the sensor is within its range and if the sensor circuit is open or shorted.

Output Device Current Flow - The PCM can see if the output devices are hooked up. If a problem exists with an output devices' circuit, the PCM can determine if it is open, shorted high, or shorted to ground.

Oxygen Sensor - Once the system has entered closed loop, the PCM checks that the oxygen sensor is switching between rich and lean.



PCM INPUTS
- A/C Request
- A/C Select
- ASD Sense
- Battery Voltage
- Brake Switch
- Camshaft Position Sensor
- Crankshaft Position Sensor
- Data Link Receive
- Engine Coolant Temp Sensor
- Generator Output
- Ignition Circuit Sense
- Intake Air Temp Sensor
- MAP Sensor
- Overdrive/Override Switch
- Oxygen Sensor
- Park/Neutral Switch
- Power Ground
- Speed Control Set Switch
- Signal Ground
- Speed Control Resume Switch
- [1][2]Throttle Position Sensor
- Vehicle Speed Sensor

PCM OUTPUTS
- A/C clutch
- Generator Field
- ASD Relay
- Data Link Transmit
- Electronic EGR Transducer
- EVAP Purge Solenoid
- Fuel Injectors
- Fuel Pump Relay
- Ignition Coil
- Idle Air Control Motor
- Malfunction Indicator Lamp
- Shift Indicator Lamp
- Speed Control Solenoids
- Tachometer

NOTE: Not all models use all inputs and outputs.