Chart 1

Diagnostic Chart:

Schematic:

Since a Scan tool is required to perform any diagnostics this is the starting point. The PCM, SDM, IPC, and ECM share same data link referred to as class II data bus.

When ignition is turned On PCM will perform a bulb test on SERVICE Lamp, Low Coolant lamp, Low Oil Pressure lamp, Charge lamp, Change Oil Soon lamp, Hot telltale lamp and MIL (SERVICE ENGINE SOON) telltale lamp. The lights should stay On 2-3 seconds after engine is started and turned Off. If any of the lamps remain On, a problem and possible DTC will exist.

If data can be read, engine starts and runs ok, and there are no DTCs stored, then diagnosis will depend on the symptoms or customer complaint.

Circuit 480 (battery keep alive) has 12 volts applied to it at all times. Information such as diagnostic trouble codes, long term fuel correction, spark adaptives, etc., requires power to retain their learned values.

Circuit 451 (ground) is grounded to the engine block.