P0646

Diagnostic Chart:

Schematic:

The ECM acts as a path to ground for the low pin of the relay to engage the A/C clutch. The ECM internal output driver is normally open, and will switch to ground when A/C is requested. This circuit is monitored continuously. If the voltage on this line should fall below a calibrated table lower limit with the driver active, this code will set.

DTC PARAMETERS
This DTC will set when:
^ Engine Speed greater than 40 rpm
^ Battery Voltage is between 7.5 and 15 volts

DTC P0646 is a (type D) DTC.

DIAGNOSTIC AIDS
To locate an intermittent problem, use the Scan tool to monitor A/C Relay command with ignition On, engine Off.

While A/C Relay command state is On, wiggling wires may engage the A/C clutch to help locate a short to ground.