System Diagnostics: Notes

CAUTION: When battery is disconnected, vehicle computer and memory systems may lose memory data. Driveability problems may exist until computer systems have completed a relearn cycle. See COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION before disconnecting battery.

NOTE: Self-diagnostic tests are written specifically for Chrysler's Diagnostic Readout Box (DRB). A generic scan tool may not be capable of performing all necessary test functions. Malfunction Indicator Light (MIL), also known as CHECK ENGINE light can be used, but has limited diagnostic capability.

The self-diagnostic capabilities of this system, if properly utilized, can simplify testing. The Powertrain Control Module (PCM) monitors several different engine control system circuits.

If a problem is sensed with a monitored circuit, PCM memory stores a trouble code, the Malfunction Indicator Light (MIL) glows and PCM enters limp-in mode. In limp-in mode, PCM compensates for component failure by substituting information from other sources. This allows vehicle operation until repairs can be made.

Test circuits and repair or replace components as required. If problem is repaired or ceases to exist, the PCM cancels trouble code after approximately 50 ignition on/off cycles on all models except LH body. On LH body, PCM cancels trouble code after approximately 50-100 ignition on/off cycles.

A specific trouble code results from a particular system failure. A trouble code does not condemn a specific component; component is not necessarily the reason for failure. Trouble codes only call out a probable malfunction area.