B1C83 Code: Meaning, Causes, and Symptoms | OBD2 Codes

B1C83 – Rear Defog Relay Circuit


B1C83 Possible Symptoms


Engine Light ON (or Service Engine Soon Warning Light)


B1C83 Possible Causes


Faulty Rear Defog Relay,Rear Defog Relay harness is open or shorted,Rear Defog Relay circuit poor electrical connection,Faulty Exterior Mirror,Faulty Heating, Ventilation, and Air-Conditioning (HVAC)


B1C83 Description


When the engine is running and the heated mirror/rear window defrost switch (integral to the Heating, Ventilation, and Air-Conditioning (HVAC) Module or Front Controls Interface Module (FCIM) if equipped with navigation system) is pressed, the HVAC module activates the rear window defrost relay. For vehicles equipped with navigation system, the FCIM sends the defrost request message to the HVAC module over the Controller Area Network (CAN). When the rear window defrost relay is active, voltage is supplied to the LH and RH exterior mirror glass and spotter mirror glass (if equipped). The LH and RH mirrors do not share the same ground circuits. The OBDII codes sets when the HVAC module senses a short to ground, short to voltage or open on the heated mirror/rear window defrost relay control circuit.