• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
• | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
• | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
---|---|---|---|---|
Relay Switch B+ | 1 | 1 | -- | -- |
Rear Defog Switch Signal | 2 | 1 | 1 | -- |
Rear Defog Relay Control | B0283 02 | B0283 05 | B0283 05 | -- |
Rear Window Defogger Grid Control | 1 | 1 | 2 | -- |
Rear Defog Indicator Control | B0283 02 | B0283 05 | B0283 05 | -- |
HVAC Ground | -- | 1 | 1 | -- |
Relay Coil Ground | -- | 1 | 1 | -- |
Rear Window Defogger Grid Ground | -- | 1 | 1 | -- |
1. Rear defogger Inoperative 2. Rear Defogger Always ON |
Battery positive voltage is supplied through the REAR DEFOG fuse, in the underhood fuse block, to the REAR DEFOG relay switched input. The BCM supplies 12 volts on the rear window defogger switch signal circuit to the HVAC control assembly. When you depress the defog switch, the rear window defogger switch pulls the signal circuit low. The BCM interprets as a request for the rear window defogger system. The BCM enables the rear window defogger system by supplying voltage to the REAR DEFOG relay coil. The relay coil supply voltage is also spliced off internally in the BCM to the supply voltage circuit of the defogger indicator. The REAR DEFOG relay is energized and the defogger indicator is illuminated. With the relay energized, battery positive voltage is allowed from the relay switched input through the switch contacts and out the relay switched output to the rear window defogger grid.
Battery voltage must be between 9-16 volts.
The BCM detects a short to ground in the relay coil control circuit or a short to ground in the defog indicator control circuit.
The BCM detects a concurrent short to voltage or an open/high resistance in both of the relay control and the rear defog indicator circuits.
The rear window defogger will not operate.
• | The DTC will be current for as long as the fault is present. |
• | When the fault is no longer present, the DTC will be a history DTC. |
• | A history DTC will clear after 50 ignition cycles. |
Rear Window Defogger Description and Operation
Control Module References for scan tool information
Ignition ON, command the Rear Defog Relay ON and OFF with a scan tool. The rear window defogger and rear window defogger indicator should turn ON and OFF when changing between the commanded states.
⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
⇒ | If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM. |
⇒ | If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM. |
⇒ | If the test lamp does not turn ON and OFF, replace the HVAC control assembly. |
⇒ | If not within the specified range, replace the relay. |
• | 30 and 86 |
• | 30 and 87 |
• | 30 and 85 |
• | 85 and 87 |
⇒ | If not the specified value, replace the relay. |
⇒ | If greater than the specified range, replace the relay. |
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Control Module References for BCM and HVAC control assembly replacement, setup and programming