B1028-19

B1028-19-HIGH BEAMS - OVER CURRENT

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.

With the high beam headlamps commanded on.

- Set Condition:
When the Body Control Module (BCM) detects higher than expected current 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 on.
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 High Beam Headlamps off.
2. Turn the ignition off.
3. Remove the High Beam Relay and substitute it with a known good relay.
4. Turn the ignition on.
5. Turn the High Beam Headlamps on.
6. With the scan tool, read DTCs.

Does the scan tool display DTC: B1028-19-HIGH BEAMS - OVER CURRENT?

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 VOLTAGE
1. Turn the ignition off.
2. Remove the High Beam Relay.
3. Disconnect the BCM C1 harness connector.
4. Turn the ignition on.
5. Measure the voltage between ground and the (L300) High Beam Relay Control circuit.

Is there any voltage present?

Yes

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

No

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