Cabin Heater

DIAGNOSIS AND TESTING - POSITIVE TEMPERATURE COEFFICIENT (PTC) HEATER UNIT

WARNING: Disable the airbag system before attempting any steering wheel, steering column or instrument panel component diagnosis or service. Disconnect and isolate the negative battery (ground) cable, then wait two minutes for the airbag system capacitor to discharge before performing further diagnosis or service. This is the only sure way to disable the airbag system. Failure to follow these instructions may result in accidental airbag deployment and possible serious or fatal injury.

NOTE: See Wiring Information for circuit descriptions and diagrams. Wiring Information includes wiring diagrams, proper wire and connector repair procedures, further details on wire harness routing and retention, as well as pin-out and location views for the various wire harness connectors, splices and grounds.

1. Using a scan tool, check for Diagnostic Trouble Codes (DTCs) related to the A/C heater module and Body Control Module (BCM). If no DTCs are found, go to Step 2. If any DTCs are found, repair as required.
2. Check the PTC relay fuses in the Power Distribution Center (PDC). If OK, go to Step 3. If not OK, repair the shorted circuit and replace the fuse(s).
3. Disconnect and isolate the negative battery cable.
4. Disconnect the wire harness connector from the PTC heater unit Cabin Heater - Removal.
5. Using an ohmmeter, check for continuity between all of the PTC heater unit terminals. In each case there should be continuity. If OK, repair the wire harness circuits between the PTC heater unit and the PDC. If NOT OK, replace the PTC heater unit.