Diagnostic Modes

The Powertrain Control Module (PCM) has two modes for transmitting information. The following information will describe the system operation in each of the modes.

NORMAL (OPEN) MODE
On engines that can be monitored in the "Open" mode, certain parameters can be observed without changing the engine operating characteristics. The parameters capable of being read vary with engine families.


DIAGNOSTIC MODE
When the diagnostic terminal is grounded with the ignition "ON" and the engine "OFF," the system will enter what is called the diagnostic mode. In this mode the PCM will:

^ Display a Diagnostic Trouble Code (DTC) 12 by flashing the Malfunction Indicator Lamp (MIL).

0R

^ Display any stored DTC by flashing the MIL. Each DTC will be flashed three times.