Diagnostic Instructions
| • | 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. |
DTC Descriptors
DTC B0283 02: Electric Rear Defrost Circuit Short To GroundDTC B0283 05: Electric Rear Defrost Circuit Short To Battery Or Open
Diagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Relay Switch B+ Circuit | 2 | 2 | -- | -- |
Rear Defogger Relay Control | B0283 02 | B0283 05 | B0283 05 | -- |
Rear Defogger Control Circuit | 2 | 2 | 1 | -- |
Relay Coil Ground | -- | 2 | 2 | -- |
Rear Window Defogger Grid Ground | -- | 2 | 2 | -- |
1. Rear Defogger Always ON 2. Rear Defogger Inoperative | ||||
Circuit/System Description
The HVAC control module monitors the voltage level on the supply voltage circuit of the DEFOG relay. The voltage level should be low while the DEFOG relay is de-energized. The voltage will be near system voltage when the HVAC control module energizes the DEFOG relay.
Conditions for Running the DTC
Battery voltage must be between 9-16 volts.
Conditions for Setting the DTC
B0283 02
This DTC will set when the HVAC control module detects a short to ground in the rear defog relay control circuit for 1 second or greater.
B0286 05
This DTC will set when the HVAC control module detects a short to voltage or an open/high resistance in the rear defog relay control circuit for 1 second or greater.
Action Taken When the DTC Sets
| • | The HVAC Control Module stores the DTC to memory. |
| • | The rear window defogger will not operate. |
Conditions for Clearing the DTC
| • | This DTC will change from current to history when the fault is no longer present. |
| • | A history DTC will clear after 100 consecutive ignition cycles if the condition for the malfunction is no longer present. |
| • | The technician issues a scan tool CLEAR DTCs command. |
Reference Information
Schematic Reference
Connector End View Reference
Window Systems Connector End Views
Description and Operation
Rear Window Defogger Description and Operation
Electrical Information Reference
| • | Circuit Testing |
| • | Wiring Repairs |
Scan Tool Reference
Circuit/System Verification
Command the rear window defogger ON and OFF with the scan tool. The rear window defogger should turn ON and OFF when changing between the commanded states.
Circuit/System Testing
- Ignition OFF, disconnect the DEFOG relay.
- Ignition OFF, test for less than 1.0 ohm of resistance between the relay coil ground circuit terminal 25 and ground.
- Connect a test lamp between the rear defogger relay control circuit terminal 39 and the relay coil ground circuit terminal 25.
- Ignition ON, command the rear defog relay ON and OFF by pressing the rear defogger switch. The test lamp should turn ON and OFF when changing between the commanded states.
- If all circuits test normal, test or replace the DEFOG relay.
| ⇒ | If greater than the specified range, test the relay coil ground circuit for an open/high resistance. |
| ⇒ | If the test lamp is always ON, test the rear defogger relay control circuit for a short to voltage. If the circuit tests normal, replace the HVAC control module. |
| ⇒ | If the test lamp is always OFF, test the rear defogger relay control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the HVAC control module. |
Component Testing
- Ignition OFF, disconnect the DEFOG relay.
- Test for 60-180 ohms of resistance between terminals 85 and 86.
- Test for infinite resistance between the following terminals:
- Install a 25-amp fused jumper wire between relay terminal 85 and 12 volts. Install a jumper wire between relay terminal 86 and ground. Test for less than 2 ohms of resistance between terminals 30 and 87.
| ⇒ | If the resistance is 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. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for HVAC control module and BCM replacement, setup and programming |
