Service Charging System P0621 DTC Stored - keywords alternator battery charge dic generator gauge light low ls2 ls7 voltage

This PI Supercedes To Include Looking For Short On Generator Bracket. Please Discard PIC4402.

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Some customers may comment of a "Service Charging System", "Service Electrical System" and/or a "Battery Voltage Low" message on the DIC accompanied by DTC P0621 in the PCM. This may be the result of a shorted wire on the generator bracket or a cut in the stator winding that is caused from high engine RPM, usually because the engine hit the rev limiter. The internal fan is flexing and when it does flex, it comes into contact with the winding. A new generator may do the same thing if the engine is placed against the rev limiter.

Inspect circuit 225 for a short to ground on the generator support bracket, where indicated in the picture below. If no wire concerns are found, replace the generator with current SPO stock.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.