On-Board Diagnostic System

SELF DIAGNOSIS OPERATION
The PCM also monitors many of its input and output circuits for faults, and if a fault is detected:

- A Diagnostic Trouble Code (DTC) is stored in memory.

- The Malfunction Indicator Lamp (MIL) is illuminated [1].

- The vehicle enters "Limp-in Mode". SEE LIMP-IN OPERATION below.

NOTE: DTC's can be read using the MIL, (previously called the Check Engine Lamp), or a scan tool. SEE DIAGNOSIS, TESTING AND INSPECTION PROCEDURES.

[1] The MIL is not illuminated for every fault, always read DTC's before attempting to diagnose a driveablity or emission related problem.

LIMP-IN OPERATION
NOTE: The vehicle has entered Limp-In if the MIL, is illuminated during vehicle operation.

Purpose
In Limp-In mode the PCM allows for limited vehicle operation, when one or more inputs is out side of limits.

The vehicle should be driven to a service facility as soon as possible.

Operation
The PCM substitutes the input of an alternate sensor for that of the failed sensor, while continueing to monitor the faulty sensor input(s).

If the faulty sensor input returns to and remains within limits for a long enough period, the PCM resumes normal operation.