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B0287



DTC B0285 or B0287

DTC Descriptors

DTC B0285
- Electric Rear Defrost Circuit Low

DTC B0287
- Electric Rear Defrost Circuit Open

Diagnostic Fault Information

Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview





Circuit/System Description

The body control module (BCM) monitors the voltage level on the supply voltage circuit of the RDFG relay. The voltage level should be low while the REAR DEFOG relay is de-energized. The voltage will be near system voltage when the BCM energizes the REAR DEFOG relay.

Conditions for Running the DTC

Battery voltage must be between 9-16 volts.

Conditions for Setting the DTC

DTC B0285

This DTC will set when the BCM detects a low voltage level in the supply circuit of the REAR DEFOG relay when the relay is energized.

DTC B0287

This DTC will set when the BCM detects an open/high resistance in the supply circuit of the REAR DEFOG relay when the relay is energized.

Action Taken When the DTC Sets

* The BCM 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.

Circuit/System Verification

Command the rear window defogger ON and OFF with the scan tool. The rear window defogger and defogger indicator should turn ON and OFF when changing between the commanded states.

If the rear window defogger does not turn ON and OFF when changing between the commanded states, refer to Rear Defogger Malfunction. Rear Window Defogger Malfunction

If the Defogger Indicator does not illuminate or continuously illuminates, refer to Rear Defogger Indicator Malfunction.

Circuit/System Testing

Rear Defogger Malfunction
1. Ignition OFF, disconnect the RR DEFOG relay.
2. Test for less than 1 ohm of resistance between the relay coil ground circuit V10 and ground.

• If greater than the specified range, test the relay coil ground circuit for an open/high resistance.

3. Connect a test lamp between the rear defogger relay control circuit U12 and the relay coil ground circuit V10.
4. Ignition ON, command the rear defog relay ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

• If the test lamp is always ON, test the rear defogger relay control circuit U12 for a short to voltage. If the circuit tests normal, replace the BCM.
• If the test lamp is always OFF, test the rear defogger relay control circuit U12 for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.

5. If all circuits test normal, test or replace the RR DEFOG relay.

Rear Defogger Indicator Malfunction
1. Ignition OFF, disconnect the harness connector C2 at the HVAC Control Assembly.
2. Ignition OFF, test for less than 1 ohm of resistance between the ground circuit terminal K and ground.

• If greater than the specified range, test the ground circuit for an open/high resistance.

3. Disconnect the RR DEFOG relay.
4. Connect a test lamp between the control circuit terminal J and ground.
5. Ignition ON, command the Rear Defog Relay ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

• 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.

6. If all circuits test normal, test or replace the HVAC Control Assembly.

Component Testing

Defogger Indicator
1. Ignition OFF, disconnect the harness at the HVAC Control Assembly.
2. Install a 5-amp fused jumper wire between circuit terminal G and 12 volts. Install a jumper wire between the ground circuit terminal K and ground. Verify the Defog Indicator illuminates.

• If the Defog Indicator does not illuminate, replace the HVAC Control Assembly.

Relay Test
1. Ignition OFF, disconnect the RDFG relay.
2. Test for 60-180 ohms of resistance between terminals 85 and 86.

• If the resistance is not within the specified range, replace the relay.

3. Test for infinite resistance between the following terminals:

* 30 and 86
* 30 and 87
* 30 and 85
* 85 and 87

• If not the specified value, replace the relay.

4. 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.
5. If greater than the specified range, replace the relay.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

* Relay Replacement (Attached to Wire Harness) Relay Replacement (Within an Electrical Center)
* Control Module References for HVAC control assembly and BCM replacement, setup, and programming Programming and Relearning
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