Powertrain Diagnosis

Diagnostic Chart:

Schematic:

The L-terminal Circuit 225 is a two-way link between the PCM and generator. The PCM supplies the generator with 5 volts whenever the ignition is On. The PCM will not supply 5 volts to the generator during engine cranking if battery voltage is below 9.6 volts. Once the engine is running, the generator must have the 5 volt supply to charge. If the generator stops charging while the engine is running, it will ground this 5 volt supply from the PCM. When the PCM detects this ground, it will send a message to the I/P cluster over the Class II link to illuminate the Charge telltale.

DTC PARAMETERS
DTC P0621 will set if generator L-terminal output voltage at the PCM is less than 4.0 volts when:
^ Condition exists for longer than 15 seconds
^ Engine is running

OR

Generator L-terminal output voltage at the PCM is greater than 4.0 volts when:
^ Condition exists for longer than 5 seconds
^ Engine is NOT running

DTC P0621 diagnostic runs continuously with ignition On.

P0621 is a type D DTC.

DIAGNOSTIC AIDS
With ignition On, engine Off, voltage measured with a DVOM on circuit 225 at the generator with the connector disconnected should read 5 volts.

A generator that is not charging with engine running will pull circuit 225 (through resistance) to ground and set this DTC.

An intermittent open or short to ground on circuit 225 will set this DTC. GENERATOR F-TERMINAL DC on Scan tool will read 0% with ignition On if this occurs.

GENERATOR F-TERMINAL DC on Scan tool should read near 17% with ignition On and engine Off.