Chart 4

Diagnostic Chart:

Schematic:

The A/C relay coil is feed ignition voltage on the high side and controlled by an Output Driver Module (ODM) in the PCM on the low side. When the PCM is not commanding the A/C relay On, it expects to see ignition voltage at the feedback. When the relay is commanded On it expects to see zero volts at the feedback.

DTC PARAMETERS
DTC P1640 will set if feedback voltage does not agree with expected voltage (based on commanded state of output).

DIAGNOSTIC AIDS
Use Scan tool to command A/C relay On or Off and monitor A/C Relay CKT feedbacks while manipulating harness to find intermittents.