Powertrain Diagnosis

Diagnostic Chart:

Schematic:

The ECM continuously monitors the signal from the generator. If the ECM detects a low voltage on the generator circuit, this DTC will set.

DTC PARAMETERS
This DTC will set when:
^ Generator L-terminal voltage falls below a calibratable lower limit
^ Engine speed greater than 40 rpm

DTC P1637 is a (type D) DTC.

DIAGNOSTIC AIDS
To locate an intermittent problem, use the Scan tool to monitor ignition 1 voltage with engine running.

Wiggling wires while monitoring ignition 1 voltage may locate where a short to ground exist.

IMPORTANT: A grounded L-terminal Circuit will cause the generator not to charge below 2500 engine rpm. Above 2500 rpm, the generator will self excite its field winding and begin to charge.