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. |
Diagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Rear Fog Lamp Relay Control | 1 | 1 | 1 | -- |
Rear Fog Lamp Switch Signal | 2 | 2 | 2 | -- |
Rear Fog Lamp Voltage Supply | 1 | 1 | 1 | -- |
Fog Lamp - LR Ground | -- | 1 | 1 | -- |
Fog Lamp - RR Ground | -- | 1 | 1 | -- |
Fog Lamp Switch Ground | -- | 2 | 2 | -- |
| ||||
Circuit/System Description
The rear fog lamp relay is supplied with battery voltage at all times. The rear fog lamp switch signal circuit is grounded momentarily by pressing the rear fog lamp switch. The body control module (BCM) energizes the rear fog lamp relay by applying ground to the rear fog lamp relay control circuit. When the rear fog lamp relay is energized, the relay switch contacts close and battery voltage is applied through the rear fog lamp supply voltage circuit which illuminates the rear fog lamps. For more detailed information concerning fog lamp operation refer to Exterior Lighting Systems Description and Operation .
Reference Information
Schematic Reference
Connector End View Reference
Lighting Systems Connector End Views
Electrical Information Reference
Scan Tool Reference
Circuit/System Verification
Ignition ON, observe the scan tool rear fog lamp switch parameter while pressing and releasing the rear fog lamp switch. The reading should toggle between ACTIVE and INACTIVE.
| ⇒ | If the reading does not change between the commanded states, refer to Rear Fog Lamp Switch Malfunction. |
Circuit/System Testing
Rear Fog Lamp Switch Malfunction
- Ignition OFF, disconnect the harness connector at the turn signal multifunction switch.
- Ignition OFF, verify that a test lamp illuminates between B+ and the ground circuit terminal 3.
- Ignition ON, verify the scan tool rear fog lamp switch parameter is INACTIVE.
- Install a 3A fused jumper wire between the signal circuit terminal 2 and the ground circuit terminal 3. Verify the scan tool rear fog lamp switch parameter is ACTIVE.
- If all circuits test normal, test or replace the turn signal/multifunction switch.
| ⇒ | If the test lamp does not illuminate, test the ground circuit for an open/high resistance. |
| ⇒ | If not the specified value, test the signal circuit terminal 2 for a short to ground. If the circuit tests normal, replace the BCM. |
| ⇒ | If not the specified value, test the signal circuit terminal 2 for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM. |
Rear Fog Lamps Malfunction
- Ignition OFF, disconnect the rear fog lamp relay.
- Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal R33 and ground.
- Verify that a test lamp illuminates between the B+ circuit terminal R31 and ground.
- Verify that a test lamp illuminates between the B+ circuit terminal R32 and ground.
- Disconnect the harness connector at the inoperative rear fog lamp.
- Ignition OFF, scan tool OFF, exterior lamps OFF, test for less than 5.0 ohms of resistance between the inoperative front fog lamp ground circuit terminal B and ground.
- Connect the harness connector at the inoperative rear fog lamp.
- Connect a 15A fused jumper wire between the B+ circuit terminal R32 and the relay controlled output circuit terminal R33. Verify the rear fog lamps are activated.
- Connect a test lamp between the B+ circuit terminal R31 and the control circuit terminal R35
- Command the rear fog lamps ON and OFF with the rear fog lamp switch. The test lamp should turn ON and OFF when changing between the commanded states.
- If all circuits test normal, test or replace the rear fog lamp relay.
| ⇒ | If the test lamp illuminates, test the control circuit for a short to voltage. |
| ⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, test the control circuit terminal R33 for a short to ground. If the circuit tests normal, test or replace the rear fog lamp relay. |
| ⇒ | If the test lamp does not illuminate, test the B+ circuit for an open/high resistance. |
| ⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
| ⇒ | If the rear fog lamps do not activate, test the relay controlled output circuit terminal R33 for an open/high resistance. If the circuit tests normal, test or replace the inoperative rear fog lamp. |
| ⇒ | If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the BCM. |
| ⇒ | If the test lamp is always OFF, test the control circuit for a short to voltage or open/high resistance. If the circuit tests normal, replace the BCM. |
Rear Fog Lamp Indicator Malfunction
Ignition ON, with a scan tool perform the display test for the instrument panel cluster (IPC) and observe the rear fog lamp indicator
| ⇒ | If the rear fog lamp indicator illuminates during the test, replace the BCM. |
| ⇒ | If the rear fog lamp indicator does not illuminate during the test or remains illuminated at all times, replace the IPC. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for BCM or IPC replacement, setup, and programming |
