Auxiliary Cabin Heater: Testing and Inspection

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 take the proper precautions could result in accidental airbag deployment and possible personal injury or death.

NOTE: For circuit descriptions and diagrams, refer to the appropriate wiring information. The 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.

Prior to replacing the positive temperature coefficient (PTC) heater unit, check for any diagnostic trouble codes (DTCs) related to the engine control module (ECM), front control module (FCM) and the heating-A/C system and repair as necessary. Also, run the calibration procedure to verify that the concern is not a heating-A/C system issue Heating-A/C System Diagnostics and to 24 - HVAC Electrical Diagnostics for more information.

1. Disconnect and isolate the negative battery cable.
2. Disconnect the wire harness connector from the PTC heater unitRemoval.
3. 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 ECM and the FCM. If NOT OK, replace the PTC heater unit.