B1028-14

B1028-14-HIGH BEAMS - CIRCUIT SHORT TO GROUND OR OPEN

For a complete wiring diagram, refer to the Wiring Information.

Theory of Operation

The Body Control Module (BCM) receives the input from the Left Multi-function Switch indicating that high beam lamp illumination is requested. The BCM provides a ground path through the high beam relay control circuit. The high beam relay control circuit connects to the High Beam or Main Headlights Relay, which when energized provides voltage to the shutters in the Headlamps. The High Beam or Main Headlights Relay is located in the Power Distribution Center. For additional information on the Headlamps operation, Exterior Lamps - Operation.

- When Monitored:
With the ignition on.

High beam headlamps off.

- Set Condition:
When the Body Control Module (BCM) detects a low condition on the (L300) High Beam Relay Control circuit.





1. CHECK FOR AN INTERMITTENT CONDITION
1. Turn the ignition on.
2. With the scan tool, clear all DTCs.
3. Turn the High Beam Headlamps off.
4. With the scan tool, read DTCs.

Does the scan tool display this DTC as active?

Yes

- Go To 2

No

- Test complete, the condition or conditions that originally set this DTC are not present at this time. Using the wiring diagrams as a guide, check all related splices and connectors for signs of water intrusion, corrosion, pushed out or bent terminals, and correct pin tension.
- Perform the BODY VERIFICATION TEST. Body Verification Test.

2. CHECK THE HIGH BEAM RELAY
1. Turn the ignition off.
2. Remove the High Beam Relay and substitute it with a known good relay.
3. Turn the ignition on.
4. With the scan tool, read DTCs.

Does the scan tool display DTC: B1028-14-HIGH BEAMS - CIRCUIT SHORT TO GROUND OR OPEN?

Yes

- Go To 3

No

- Replace the High Beam Relay.
- Perform the BODY VERIFICATION TEST. Body Verification Test.

3. CHECK THE (L300) HIGH BEAM RELAY CONTROL CIRCUIT FOR A SHORT TO GROUND
1. Turn the ignition off.
2. Remove the High Beam Relay.
3. Disconnect the BCM C1 harness connector.
4. Measure the resistance between ground and the (L300) High Beam Relay Control circuit.

Is the resistance above 10k Ohms?

Yes

- Go To 4

No

- Repair the short to ground in the (L300) High Beam Relay Control circuit.
- Perform the BODY VERIFICATION TEST. Body Verification Test.

4. CHECK THE (L300) HIGH BEAM RELAY CONTROL CIRCUIT FOR AN OPEN
1. Measure the resistance of the (L300) High Beam Relay Control circuit between the High Beam Relay and the BCM C1 harness connector.

Is the resistance below 5.0 Ohms?

Yes

- Replace the Body Control Module (BCM). Body Control Module - Removal.
- Perform the BODY VERIFICATION TEST. Body Verification Test.

No

- Repair the open in the (L300) High Beam Relay Control circuit.
- Perform the BODY VERIFICATION TEST. Body Verification Test.