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 provide 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 |
|---|---|---|---|---|
Rear Defog Relay Switch B+ | 1 | 1 | -- | -- |
Rear Defog Relay Control | B0283 02 | B0283 05 | B0283 05 | -- |
Rear Defog Relay Switch Control | 1 | 1 | 1 | -- |
Rear Defog Relay Coil Ground | -- | B0283 05 | -- | -- |
Rear Window Defogger Grid Ground | -- | 1 | -- | -- |
1. Rear Window Defogger Malfunction | ||||
Circuit/System Description
When the rear window defogger switch is activated, the radio/HVAC control panel sends a serial data message to the HVAC control module requesting the rear defogger be activated. The HVAC control module responds by energizing the rear defog relay by applying voltage to the rear defog relay control circuit. When the rear defog relay coil is energized, the switch contacts of the rear defog relay close allowing battery voltage to flow from the REAR DEFOG fuse through the closed switch contacts and out the relay switched output to the rear window defogger grid.
Conditions for Running the DTC
Battery voltage is between 9-16 volts.
Conditions for Setting the DTC
B0283 02
The HVAC control module detects a short to ground in the rear defog relay control circuit for 1 second or greater.
B0283 05
The HVAC control module detects a short to voltage or an open/high resistance in the rear defog relay control circuit or an open/high resistance it the rear defog relay ground circuit for greater than 1 second.
Action Taken When the DTC Sets
B0283 02
The rear window defogger will be inoperative.
B0283 05
The rear window defogger will be inoperative or will operate continuously.
Conditions for Clearing the DTC
| • | 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. |
Reference Information
Schematic Reference
Connector End View Reference
Description and Operation
Rear Window Defogger Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
Command the Rear Defog Request 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 REAR DEFOG relay.
- Test for less than 1 ohm between the ground circuit terminal 85 and ground.
- Connect a test lamp between the control circuit terminal 86 and the ground circuit terminal 85.
- Ignition ON, command Rear Defog Request ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
- If all circuits test normal, test or replace the REAR DEFOG relay.
| ⇒ | 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 HVAC control module. |
| ⇒ | 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 HVAC control module. |
Component Testing
Relay Test
- Ignition OFF, disconnect the REAR DEFOG relay.
- Test for 60-180 ohms 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 between terminals 30 and 87.
| ⇒ | 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. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for HVAC control module replacement, setup, and programming |
