Headlamp Low or High Beams Always On V6 and V8
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Headlights/Daytime Running Lights (DRL) Schematics Connector End View Reference: Master Electrical Component List | |||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |
2 | Turn the headlamp switch to the OFF position. Do the low and high beam headlamps remain OFF? | Go to Testing for Intermittent Conditions and Poor Connections | Go to Step 3 |
3 | Remove the appropriate low or high relay. Do the lamps turn OFF? | Go to Step 5 | Go to Step 4 |
4 | Repair a short to battery positive voltage in the supply circuit of the affected headlamps. Refer to Wiring Repairs . Did you complete the repair? | Go to Step 13 | -- |
5 |
Do the headlamps turn OFF? | Go to Step 12 | Go to Step 6 |
6 | Are the high beam headlamps on at all times? | Go to Step 7 | Go to Step 8 |
7 | Test for a short to ground in FTP circuit and the high beam headlamp signal circuit. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 13 | Go to Step 9 |
8 | Test for a short to ground in the headlamp switch ON signal circuit. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 13 | Go to Step 9 |
9 | Test for a open in the exterior lamp off circuit. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 13 | Go to Step 10 |
10 | Test for a short to ground in the appropriate low or high beam relay control circuit. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 13 | Go to Step 11 |
11 | Replace the appropriate low or high relay. Refer to Relay Replacement . Did you complete the replacement? | Go to Step 13 | -- |
12 | Replace the multifunction turn signal switch. Refer to Turn Signal Multifunction Switch Replacement . Did you complete the replacement? | Go to Step 13 | -- |
13 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Step 3 |
Headlamp Low or High Beams Always On V8 High Beam PCB Relay
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 |
|---|---|---|---|---|
High Beam Headlamp Relay Control Circuit | 2 | 1 | B2580 | -- |
| ||||
Circuit/System Description
Voltage is applied at all times to the high beam headlamp relay from battery voltage. When the dimmer switch or the flash to pass switch send a ground input to the Body Control Module (BCM), the BCM sends a ground output to the high beam relay. The high beam relay is activated then the switch side of the relay closes and turns on the lights.
Reference Information
Schematic Reference
Headlights/Daytime Running Lights (DRL) Schematics
Connector End View Reference
Lighting Systems Connector End Views
Electrical Information Reference
Scan Tool Reference
Circuit/System Verification
- Ignition ON, turn the park lamps and head lamps ON. Switch the head lamps from low to high beam. The low beam and high beam lamps should illuminate.
- Observe the scan tool high beam lamps switch parameter while switching the head lamps from low to high beam. The reading should change between ON and OFF.
| ⇒ | If the high beam lamps do not illuminate and the high beam lamp switch parameter does not change while switching the head lamps from low to high beam--Test input side of BCM for inoperative condition in Circuit/System Testing. |
| ⇒ | If the high beam lamps do not illuminate and the high beam lamp switch parameter does change between ON and OFF while switching the head lamps from low to high beam--Test output side of BCM for inoperative condition in Circuit/System Testing. |
Circuit/System Testing
Test Input Side of BCM For Inoperative High Beam Lamps
- Ignition OFF, disconnect the malfunction turn signal lever harness connector at the switch.
- Test for less than 1 ohm of resistance between the ground circuit terminal D and ground.
- Ignition ON, verify the scan tool high beam lamp switch parameter displays OFF.
- Install a 3A fused jumper wire between the signal circuit terminal E and the ground circuit terminal D. Verify the scan tool high beam switch parameter displays closed.
- If all circuits test normal, test or replace the multifunction turn signal lever.
| ⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
| ⇒ | If not the specified value, test the signal circuit terminal E for a short to ground. If the circuit tests normal, replace the body control module. |
| ⇒ | If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the body control module. |
Test Output Side of BCM For Inoperative High Beam Lamps
- Disconnect the harness connector at both high beam lamps.
- Test for less than 1.0 ohm of resistance between the appropriate high beam lamp ground circuit terminal B and ground.
- Connect a test lamp between the control circuit terminal A and ground.
- Command the high beam lamps 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, replace the appropriate high beam lamp bulb socket.
| ⇒ | 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 BEC. |
| ⇒ | If the test lamp is always OFF and the circuit fuse is good, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the BEC. |
| ⇒ | If the test lamp is always OFF and the circuit fuse is open, test the control circuit for a short to ground. If the circuit tests normal, replace the appropriate high beam lamp bulb socket. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for BCM replacement, setup, and programming |
