Headlamps Malfunction
| Headlamps Malfunction |
| Diagnostic Instructions |
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Perform the
Diagnostic System Check - Vehicle
prior to using this diagnostic procedure.
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Review
Strategy Based Diagnosis
for an overview of the diagnostic approach.
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Diagnostic Procedure Instructions
provides an overview of each diagnostic category.
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| Diagnostic Fault Information |
| Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
| Ambient Light Sensor Signal | B2645 03 | B2645 03 | B2645 07 | - |
| Headlamp Switch Park Lamp Signal | 2 | B257A 00 | 2 | - |
| Headlamp Switch On Signal | B257A 00 | 1 | 1 | - |
| Headlamp Switch Headlamps Off Signal | B257A 00 | 1 | 1 | - |
| Left Headlamp Control | B2575 02 | B2575 04 | B2575 01 | - |
| Right Headlamp Control | B2699 02 | B2699 04 | B2699 01 | - |
| Inside Air Temperature Sensor Low Reference | - | B0163 05, B0183 05, B1405 05, B2645 07 | - | - |
| Headlamp Switch Ground | - | 1 | - | - |
| 1. Headlight Auto Function Only 2. Headlight Auto Function Disabled | ||||
| Circuit/System Description |
The vehicle headlamps are controlled by the body control module (BCM) based on inputs from the headlamp switch and the turn signal/multifunction switch. The headlamp switch has four positions: OFF, AUTOMATIC LIGHT, PARKING LIGHT, and LOW BEAM. The default headlamp switch position is AUTOMATIC LIGHT, in which the BCM uses the ambient light sensor to determine when headlamps are needed. The OFF portion of the headlamp switch is a momentary switch which overrides the automatic headlamp and will turn OFF the vehicle headlamps. When in the OFF position, the headlamp switch grounds the headlamp switch headlamps OFF signal circuit, prompting the BCM to turn OFF the headlamps. The Park position of the headlamp switch will only illuminate the vehicle parking lamps. The LOW BEAM position of the headlamp switch will illuminate both the parking lamps, as well has the headlamps. With the headlamp switch in the LOW BEAM position, the headlamp switch headlamps on signal circuit is grounded, prompting the BCM to turn on the headlamps, regardless of other factors such as ambient light.
The headlamp high beams are controlled through the flash to pass switch and the headlamp dimmer switch, both located in the turn signal/multifunction switch. The flash to pass switch is a momentary type switch, designed to illuminate the high beams as long as the switch is held. With the switch closed, the flash to pass switch signal circuit is grounded, prompting the BCM to turn on the high beam lamps. The headlamp dimmer switch allows the operator to select between full time high or low beam operation. Unlike the flash to pass switch, it is not a momentary switch. When the headlamp dimmer switch is in the high beam position, the headlamp dimmer switch high beam signal circuit is grounded. This prompts the BCM to turn on the high beam lamps.
| Reference Information |
Schematic Reference
Headlights/Daytime Running Lights (DRL) Schematics
Connector End View Reference
Component Connector End Views
Description and Operation
Exterior Lighting Systems Description and Operation
Electrical Information Reference
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Circuit Testing
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Connector Repairs
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Testing for Intermittent Conditions and Poor Connections
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Wiring Repairs
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Scan Tool Reference
Control Module References for scan tool information
| Circuit/System Verification |
| 1. |
Ignition ON, observe the scan tool Ambient Light Sensor parameter. The reading should be between 1.4-4.5 V and change with ambient light changes.
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| 2. |
If greater or less than the specified range, refer to Ambient Light Sensor Malfunction.
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| 3. |
Observe the scan tool Automatic Headlamp Disable Switch parameter while cycling the headlamp switch between the AUTOMATIC LIGHT and OFF positions. The parameter should cycle between Active and Inactive.
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| 4. |
If the value does not change, refer to Headlamp Switch Malfunction.
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| 5. |
Observe the scan tool Headlamp ON Switch parameter while cycling the headlamp switch between the AUTOMATIC LIGHT and LOW BEAM ON position. The parameter should cycle between Active and Inactive.
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| 6. |
If the value does not change, refer to Headlamp Switch Malfunction.
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| 7. |
Observe the function of the E4G headlamp-left low beam and the E4F headlamp-right low beam while commanding the low beam lamps ON and OFF with a scan tool. The E4G headlamp-left low beam and the E4F headlamp-right low beam should turn ON and OFF while changing between the commanded states.
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| 8. |
If the E4G headlamp-left low beam and the E4F headlamp-right low beam are always ON or always OFF, refer to Low Beam Headlamp Malfunction.
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| 9. |
Observe the scan tool High Beam Select Switch parameter while selecting the S78 turn signal/multifunction switch between the high beam position and the low beam position. The value should change between Inactive and Active while selecting between the two positions.
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| 10. |
If a value does not change between the commanded states, refer to Turn Signal/Multifunction Switch Malfunction.
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| 11. |
Observe the scan tool Headlamps Flash Switch parameter while pulling and releasing the S78 turn signal/multifunction switch. The value should be Inactive and change to Active as the switch is pulled and released
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| 12. |
If a value does not change between the commanded states, refer to Turn Signal/Multifunction Switch Malfunction.
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| 13. |
Command the High Beams ON and OFF with a scan tool. The E4E headlamp-left high beam and the E4F right high beam should turn ON and OFF when changing between the selected states.
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| 14. |
If the E4E headlamp-left high beam or the E4F right high beam low beam is always OFF, refer to High Beam Headlamps Inoperative
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| 15. |
If both high beam headlamps are always ON or always OFF, refer to High Beam Command Malfunction.
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| Circuit/System Testing |
Ambient Light Sensor Malfunction
| 1. |
Ignition OFF, disconnect the harness connector at the B10B Ambient Light/Sunload Sensor.
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| 2. |
Ignition ON, test for 4.8-5.2 V between the signal circuit terminal 5 and ground.
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| 3. |
If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the K9 BCM.
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| 4. |
If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K9 BCM.
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| 5. |
If all circuits test normal, replace the B10B Ambient Light/Sunload Sensor.
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Headlamp Switch Malfunction
| 1. |
Ignition OFF, disconnect the harness connector at the S30 headlamp switch.
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| 2. |
Ignition OFF, test for less than 30 Ω between the ground circuit terminal 6 and ground.
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| 3. |
If greater than the specified range, test the ground circuit for an open/high resistance.
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| 4. |
Ignition ON, verify the scan tool Park Lamps Switch parameter is Inactive.
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| 5. |
If not the specified value, test the signal circuit terminal 3 for a short to ground. If the circuit tests normal, replace the K9 BCM.
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| 6. |
Install a 3 A fused jumper wire between the signal circuit terminal 3 and the ground circuit terminal 6. Verify the scan tool Park Lamps Switch is Active.
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| 7. |
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 K9 BCM.
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| 8. |
Verify the scan tool Headlamps On Switch parameter is Inactive.
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| 9. |
If not the specified value, test the signal circuit terminal 4 for a short to ground. If the circuit tests normal, replace the K9 BCM.
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| 10. |
Install a 3 A fused jumper wire between the signal circuit terminal 4 and the ground circuit terminal 6. Verify the scan tool Headlamps On Switch is Active.
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| 11. |
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 K9 BCM.
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| 12. |
Verify the scan tool Automatic Headlamps Disable Switch parameter is Inactive.
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| 13. |
If not the specified value, test the signal circuit terminal 5 for a short to ground. If the circuit tests normal, replace the K9 BCM.
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| 14. |
Install a 3 A fused jumper wire between the signal circuit terminal 5 and the ground circuit terminal 6. Verify the scan tool Automatic Headlamps Disable Switch is Active.
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| 15. |
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 K9 BCM.
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| 16. |
If all circuits test normal, test or replace the S30 headlamp switch.
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Low Beam Headlamp Malfunction
| 1. |
Ignition OFF, disconnect the harness X1 harness connector at the K9 BCM.
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| 2. |
Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal listed below and ground:
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B+ circuit terminal 3
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B+ circuit terminal 4
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| 3. |
If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
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| 4. |
Ignition OFF, connect the harness X1 harness connector at the K9 BCM.
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| 5. |
Disconnect the inline harness connector at the appropriate E4 headlamp-low beam listed below:
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E4G headlamp-left low beam X115 inline harness connector
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E4F headlamp-right low beam X116 inline harness connector
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| 6. |
Connect a test lamp between the control circuit terminal G and ground.
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| 7. |
Ignition ON, command the low beam lamps ON and OFF with a scan tool. The test lamp should turn ON and OFF while changing between the commanded states.
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| 8. |
If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the K9 BCM.
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| 9. |
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 K9 BCM
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| 10. |
If all circuits test normal, replace the headlamp bulb or the headlamp.
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Turn Signal/Multifunction Switch Malfunction
| 1. |
Ignition OFF, disconnect the harness connector at the S78 turn signal/multifunction switch.
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| 2. |
Ignition OFF, test for less than 30 Ω between the ground circuit terminal 3 and ground.
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| 3. |
If greater than the specified range, test the ground circuit for an open/high resistance.
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| 4. |
Ignition ON, verify the scan tool Headlamps Flash Switch parameter is Inactive.
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| 5. |
If not the specified value, test the signal circuit terminal 4 for a short to ground. If the circuit tests normal, replace the K9 BCM.
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| 6. |
Install a 3 A fused jumper wire between the signal circuit terminal 4 and ground. Verify the scan tool Headlamps Flash Switch parameter is Active.
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| 7. |
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 K9 BCM.
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| 8. |
Verify the scan tool High Beam Select Switch parameter is Inactive.
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| 9. |
If not the specified value, test the signal circuit terminal 2 for a short to ground. If the circuit tests normal, replace the K9 BCM.
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| 10. |
Install a 3 A fused jumper wire between the signal circuit terminal 2 and ground. Verify the scan tool High Beam Select Switch parameter is Active.
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| 11. |
If not the specified value, test the signal circuit for a short to voltage or and open/high resistance. If the circuit tests normal, replace the K9 BCM.
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| 12. |
If all circuits test normal, test or replace the S78 turn signal/multifunction switch.
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High Beam Headlamps Inoperative
| 1. |
Connect a 10A fused jumper wire between the HI BEAM-LT fuse test point and B+. Verify that the E4E headlamp-left high beam is illuminated.
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| 2. |
If the E4E headlamp-left high beam does not illuminate, test the control circuit terminal 27 X3 at the X50A fuse block-underhood for a short to ground or an open/high resistance. If the circuit tests normal, replace the E4E headlamp-left high beam.
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| 3. |
Connect a 10A fused jumper wire between the HI BEAM-RT fuse test point and B+. Verify that the E4F headlamp-right high beam is illuminated.
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| 4. |
If the E4F headlamp-right high beam does not illuminate, test the control circuit terminal 26 X3 at the X50A fuse block-underhood for a short to ground or an open/high resistance. If the circuit tests normal, replace theE4F headlamp-right high beam.
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High Beam Command Malfunction
| 1. |
Ignition OFF, disconnect the X5 harness connector at the K9 BCM.
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| 2. |
Ignition ON, test for greater than 10V between the control circuit terminal 18 and ground.
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| 3. |
If less than the specified range, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the X50A fuse block-underhood.
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| 4. |
Connect a 5A fused jumper wire between the control circuit terminal 18 and ground. Verify that the E4E headlamp-left high beam and the E4F right high beam is illuminated.
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| 5. |
If the E4E headlamp-left high beam and the E4F right high beam is not illuminated, test the control circuit for a short to voltage. If the circuit tests normal, replace the X50A fuse block-underhood.
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| 6. |
If all circuits test normal, replace the K9 BCM.
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| Repair Instructions |
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
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Headlamp Replacement (T84 T85)
Headlamp Replacement (TT6 HID)
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Headlamp Switch Replacement
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Sun Load Temperature and Daytime Running Lamp Ambient Light Sensor Replacement
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Control Module References
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