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
has overviews of all diagnostic categories.
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| Diagnostic Fault Information |
| Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
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Low Beam Headlamp Supply Voltage
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1
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1
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3
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-
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High Beam Headlamp Supply Voltage
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2
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2
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4
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-
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Headlamp Low Beam Relay Control
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3
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1
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1
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-
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Headlamp High Beam Relay Control
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4
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2
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1
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-
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Headlamp Switch Headlamps OFF Signal
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B257A 00
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6
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6*
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-
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Headlamp Switch Headlamps On Signal
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B257A 00
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1
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1*
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-
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Park Lamp Switch ON Signal
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B257A 00
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B257A 00
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B257A 00*
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-
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Flash to Pass Switch Signal
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4
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5
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5
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-
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Headlamp Dimmer Switch High Beam Signal
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4
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2
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2
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-
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Low Beam Headlamp Ground
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-
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1
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-
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-
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High Beam Headlamp Ground
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-
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2
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-
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-
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Headlamp Switch Ground
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-
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1, 2
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-
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-
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Turn Signal/Multifunction Switch Ground
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-
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2, 5
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-
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-
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* Internal damage to the headlamp switch may occur if shorted to B+
1. Low Beam Headlamps Inoperative 2. High Beam Headlamp(s) Inoperative 3. Low Beam Headlamp(s) always ON 4. High Beam Headlamp(s) always ON 5. Flash to Pass Inoperative 6. Headlamp Defeat Inoperative |
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| 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.
With High Intensity Discharge (HID) Headlamps RPO TT2
The BCM controls the headlamps based on the inputs explained above. When a low beam request is received, the BCM grounds the headlamp low beam relay control circuit. This energizes the coil in the headlamp low beam relay, causing the relay switch to close. This then applies B+ to both dipped beam high intensity discharge (HID) headlights through the left and right low beam fuses so as to illuminate the low beam headlights. The BCM transmits a high beam request message to the headlight control unit in order to lift the light distribution shutter from the xenon lamp. This causes the xenon lamp to illuminate the headlamp at full brightness.With High Intensity Discharge (HID) Headlamps RPO TT6
The BCM controls the headlamps based on the inputs explained above. When a low beam request is received, the BCM grounds the headlamp low beam relay control circuit. This energizes the coil in the headlamp low beam relay, causing the relay switch to close. This then applies B+ to both low beam high intensity discharge (HID) headlamps through the left low beam and right low beam fuses, illuminating the low beam headlamps. When a high beam request is received, the BCM grounds the headlamp high beam relay control circuit. This energizes the coil in the high beam relay, causing the relay switch to close. This then applies B+ to both low beam HID headlamps through the left high beam and right high beam fuses, illuminating the high beam headlamps.Without High Intensity Discharge (HID) Headlamps RPO TT4
The BCM controls the headlamps based on the inputs explained above. When a low beam request is received, the BCM supplies an B+ through the headlamp low beam relay for the left headlamp and through daytime running lamp relay - right for the right headlamp. This then applies B+ to the low beam headlamps, illuminating the low beam headlamps. When a high beam request is received, the BCM grounds the headlamp high beam relay control circuit. This energizes the coil in the headlamp high beam relay, causing the relay switch to close. This then applies B+ to both high beam headlamps through the left high beam and right high beam fuses, illuminating the high beam headlamps.| 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 information on diagnostic tools
| Circuit/System Verification |
| 1. |
Ignition ON, observe the diagnostic tool's parameter Automatic Headlamp Disable Switch while cycling the headlamp switch between the positions AUTOMATIC LIGHT and OFF. The parameter should cycle between Active and Inactive.
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| 2. |
If the parameter does not cycle between the specified values, refer to Headlamp Switch Malfunction.
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| 3. |
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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| 4. |
If the parameter does not cycle between the specified values, refer to Headlamp Switch Malfunction.
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| 5. |
With dipped beam ON, observe the scan tool Headlamps Flash Switch parameter while pulling and releasing the turn signal/multifunction switch. The parameter should cycle between Active and Inactive.
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| 6. |
If the parameter does not cycle between the specified values, refer to Turn Signal/Multifunction Switch Malfunction.
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| 7. |
With the low beams ON, observe the scan tool High Beam Select Switch parameter while switching the headlamp dimmer switch between the low and high beam positions. The parameter should cycle between Active and Inactive.
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| 8. |
If the parameter does not cycle between the specified values, refer to Turn Signal/Multifunction Switch Malfunction.
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| 9. |
Command the Low Beams ON and OFF with a scan tool. Verify the low beam headlamps turn ON and OFF.
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| 10. |
If the low beam headlamps do not cycle between the commanded states, refer to Low Beam Headlamp Malfunction.
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| 11. |
Command the High Beams ON and OFF with a scan tool. Verify the low beam headlamps turn ON and OFF.
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| 12. |
If the high beam headlamps do not cycle between the commanded states, refer to High Beam Headlamp Malfunction.
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| Circuit/System Testing |
Headlamp Switch Malfunction
| 1. |
Ignition OFF, disconnect the harness connector at the S30 Headlamp Switch.
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| 2. |
Verify that a test lamp illuminates between the ground circuit terminal 6 and B+.
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| 3. |
If the test lamp does not illuminate, test the ground circuit for an open circuit/high resistance.
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| 4. |
Ignition ON, test for B+ between the signal circuit terminals listed below and ground.
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Headlamp switch low beams ON signal terminal 4
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Park lamp switch ON signal terminal 3
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Headlamp switch OFF signal terminal 5
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| 5. |
If less than the specified value, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K9 Body Control Module.
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| 6. |
Install a 3 A fused jumper wire between the park lamp ON signal circuit S30 Headlamp Switch terminal 3 and ground. Verify the scan tool Parklamp Switch parameter changes from ACTIVE to INACTIVE.
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| 7. |
If always Inactive, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K9 Body Control Module.
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| 8. |
If always active, test the signal circuit for a short to ground. If the circuit tests normal, replace the K9 Body Control Module.
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| 9. |
Install a 3 A fused jumper wire between the low beams ON signal circuit terminal 4 and ground. Check that the diagnostic tool's parameter Headlamp ON Switch changes from INACTIVE to ACTIVE.
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| 10. |
If always Inactive, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K9 Body Control Module.
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| 11. |
If always active, test the signal circuit for a short to ground. If the circuit tests normal, replace the K9 Body Control Module.
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| 12. |
Remove the jumper wire. Install a 3 A fused jumper wire between the signal circuit terminal 5 and ground. Verify the scan tool Automatic Headlamp Disable Switch parameter is ACTIVE.
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| 13. |
If always Inactive, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K9 Body Control Module.
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| 14. |
If always active, test the signal circuit for a short to ground. If the circuit tests normal, replace the K9 Body Control Module.
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| 15. |
If all circuits test normal, replace the S30 Headlamp Switch.
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Turn Signal/Multifunction Switch Malfunction
| 1. |
Ignition OFF, disconnect the harness connector at the turn S78 Turn Signal/Multifunction Switch.
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| 2. |
Ignition OFF, test for less than 5.0 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 Body Control Module.
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| 6. |
Verify the scan tool High Beam Select Switch parameter is Inactive.
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| 7. |
If not the specified value, test the signal circuit terminal 2 for a short to ground. If the circuit tests normal, replace the K9 Body Control Module.
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| 8. |
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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| 9. |
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 Body Control Module.
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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 Body Control Module.
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| 12. |
If all circuits test normal, test or replace the S78 Turn Signal/Multifunction Switch.
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Low Beam Headlamp Malfunction - with HID Headlamps RPO TT2/TT6
| 1. |
Ignition OFF, disconnect the appropriate harness connector at the inoperative headlamps listed below:
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E13L Headlamp Assembly - Left
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E13R Headlamp Assembly - Right
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| 2. |
Test for less than 5 Ω between the appropriate headlamp ground circuit harness connector terminal 8 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. |
Remove the appropriate fuse listed below:
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F50 UA Left Low Beam
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F49 UA Right Low Beam
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| 5. |
Ignition ON, verify that the appropriate headlamp does not illuminates.
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| 6. |
If the headlamp does illuminates, test the fuse output circuit for a short to voltage.
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| 7. |
Install a 10 A fused jumper wire between appropriate fuse output contact and B+. Verify that the appropriate low beam illuminates.
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| 8. |
If the headlamp does not illuminates, test the fuse output circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the appropriate bulb.
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| 9. |
Ignition OFF, disconnect the X5 harness connector at the K9 Body Control Module.
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| 10. |
Ignition ON, test for greater than 11 V between the control circuit terminal 13 X5 and ground.
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| 11. |
If less than the specified value, test the signal 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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| 12. |
If all circuit test normal, replace the K9 Body Control Module.
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Low Beam Headlamp Malfunction - without HID Headlamps RPO TT4
| 1. |
Ignition OFF, disconnect the appropriate harness connector at the inoperative headlamps listed below:
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E13L Headlamp Assembly - Left
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E13R Headlamp Assembly - Right
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| 2. |
Test for less than 5 Ω between the appropriate headlamp ground circuit harness connector terminal listed below and ground:
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E13L Headlamp Assembly - Left Low Beam harness connector terminal 10
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E4H Headlamp - Right Low Beam harness connector terminal 10
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If greater than the specified value, test the appropriate ground circuit for an open circuit/high resistance.
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| 3. |
Disconnect the KR49 Headlamp Low Beam Relay.
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| 4. |
Install a 10 A fused jumper wire between the relay control circuit terminal 30 and control circuit terminal 85.
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| 5. |
Command the appropriate Low Beam test ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
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| 6. |
If the test lamp is always OFF, test the appropriate control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K9 Body Control Module.
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| 7. |
If the test lamp is always ON, test the appropriate control circuit for a short to voltage. If the circuit tests normal, replace the K9 Body Control Module.
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| 8. |
If all circuits test normal, test or replace the KR49 Headlamp Low Beam Relay.
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High Beam Headlamp Malfunction - without HID Headlamps RPO TT4
| 1. |
Ignition OFF, disconnect the appropriate harness connector at the inoperative headlamps listed below:
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E13L Headlamp Assembly - Left
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E13R Headlamp Assembly - Right
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| 2. |
Test for less than 5 Ω between the appropriate headlamp ground circuit harness connector terminal 10 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. |
Remove the appropriate fuse listed below:
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F38 UA Left High Beam
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F37 UA Right High Beam
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| 5. |
Verify that the headlamp does not illuminates.
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| 6. |
If the headlamp does illuminates, test the signal circuit for a short to voltage.
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| 7. |
Install a 10 A fused jumper wire between appropriate fuse output contact and B+. Verify that the appropriate high beam illuminates.
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| 8. |
If the high beam lamp does not illuminates, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the appropriate bulb.
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| 9. |
Ignition OFF, disconnect the X5 harness connector at the K9 Body Control Module.
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| 10. |
Ignition ON, test for greater than 11 V between the control circuit terminal 18 X5 and ground.
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| 11. |
If less than the specified value, test the signal 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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| 12. |
If all circuit test normal, replace the K9 Body Control Module.
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High Beam Headlamp Malfunction - with HID Headlamps RPO TT6
| 1. |
Ignition OFF, disconnect the appropriate harness connector at the inoperative headlamps listed below:
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E13L Headlamp Assembly - Left
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E13R Headlamp Assembly - Right
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| 2. |
Test for less than 5 Ω between the appropriate headlamp ground circuit harness connector terminal 10 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. |
Remove the appropriate fuse listed below:
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F38 UA Left High Beam
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F37 UA Right High Beam
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| 5. |
Verify that the high beam shutter does not move.
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| 6. |
If the high beam shutter moves, test the signal circuit for a short to voltage.
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| 7. |
Install a 10 A fused jumper wire between appropriate fuse output contact and B+. Verify that the appropriate high beam shutter moves.
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| 8. |
If the high beam shutter does not move, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the appropriate high beam solenoid.
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| 9. |
Ignition OFF, disconnect the X5 harness connector at the K9 Body Control Module.
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| 10. |
Ignition ON, test for greater than 11 V between the control circuit terminal 18 X5 and ground.
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| 11. |
If less than the specified value, test the signal 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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| 12. |
If all circuit test normal, replace the K9 Body Control Module.
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| Component Testing |
Headlamp Switch - Static Test
| 1. |
Ignition OFF, disconnect the harness connector at the S30 Headlamp Switch.
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| 2. |
Test for infinite resistance between the signal terminal 5 and the ground terminal 6 with the switch in the AUTOMATIC LIGHT position.
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| 3. |
If not the specified value, replace the S30 Headlamp Switch.
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| 4. |
Test for infinite resistance between the signal terminal 4 and the ground terminal 6 with the switch in the AUTOMATIC LIGHT position.
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| 5. |
If not the specified value, replace the S30 Headlamp Switch.
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| 6. |
Test for infinite resistance between the signal terminal 3 and the ground terminal 6 with the switch in the PARKING LIGHT position.
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| 7. |
If not the specified value, replace the S30 Headlamp Switch.
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| 8. |
Test for less than 2.0 Ω of resistance between the signal terminal 5 and the ground terminal 6 with the switch in the OFF position.
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| 9. |
If not the specified value, replace the S30 Headlamp Switch.
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| 10. |
Test for less than 2.0 Ω of resistance between the signal terminal 4 and the ground terminal 6 with the switch in the LOW BEAM position.
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| 11. |
If not the specified value, replace the S30 Headlamp Switch.
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| 12. |
Test for less than 2.0 Ω of resistance between the signal terminal 3 and the ground terminal 6 with the switch in the PARKING LIGHT position.
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| 13. |
If not the specified value, replace the S30 Headlamp Switch.
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Turn Signal/Multifunction Switch
| 1. |
Ignition OFF, disconnect the harness at the S78 Turn Signal/Multifunction Switch.
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| 2. |
Test for infinite resistance between the signal terminal 4 and the ground terminal 3 with the flash to pass switch in the open position.
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| 3. |
If not the specified value, replace the S78 Turn Signal/Multifunction Switch.
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| 4. |
Test for infinite resistance between the signal terminal 2 and the ground terminal 3 with the headlamp dimmer switch in the LOW BEAM position.
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| 5. |
If not the specified value, replace the S78 Turn Signal/Multifunction Switch.
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| 6. |
Test for less than 2.0 Ω of resistance between the signal terminal 4 and the ground terminal 3 with the flash to pass switch in the closed position.
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| 7. |
If not the specified value, replace the S78 Turn Signal/Multifunction Switch.
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| 8. |
Test for less than 2.0 Ω of resistance between the signal terminal 2 and the ground terminal 3 with the headlamp dimmer switch in the HIGH BEAM position.
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| 9. |
If not the specified value, replace the S78 Turn Signal/Multifunction Switch.
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| Repair Instructions |
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
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Relay Replacement (Attached to Wire Harness)
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Headlamp Switch Replacement
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Turn Signal Multifunction Switch Replacement
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Headlamp Replacement
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Headlamp Bulb Replacement (Xenon - Left Side)
Headlamp Bulb Replacement (Xenon - Right Side)
Headlamp Bulb Replacement (High Beam)
Headlamp Bulb Replacement (Low Beam)
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Control Module References
for information on BCM replacement, setup, and programming
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