Headlamps Malfunction (T4A)
Headlamps Malfunction (T4A)
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) provides an overview of each diagnostic category.
Diagnostic Fault Information
Circuit/System Description
With the headlamp switch in the ON position, the headlamp switch headlamp ON signal circuit is grounded through the headlamp and panel dimmer switch. For low beam headlamp operation, the body control module (BCM) responds by applying a pulse width modulated (PWM) voltage to the left and right low beam headlamp control circuits illuminating the low beam headlamps. For high beam headlamp operation, with the turn signal/multifunction switch in the high beam position, the high beam signal circuit is supplied with ground. The BCM responds to this input by applying ground to the high beam relay control circuit. The underhood fuse block supplies battery voltage to the relay coil and switch circuits of the high beam relay. With the high beam relay coil energized, the relay switch contacts close allowing voltage to flow through the left and right HIGH BEAM fuses to the high beam headlamps. With the high beams active, the BCM sends a serial data message to the instrument cluster requesting to illuminate the high beam indicator.
Reference Information
Schematic Reference
Headlights Schematics (Headlights Schematics)
Connector End View Reference
Component Connector End Views (Connector End Views By Name)
Description and Operation
Exterior Lighting Systems Description and Operation (Exterior Lighting Systems)
Electrical Information Reference
* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing For Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information
Circuit/System Verification
1. Ignition ON, observe the scan tool Headlamp On Switch parameter while turning the headlamp switch ON and OFF. The reading should toggle between Active and Inactive.
• If the reading does not change between the commanded states, refer to Headlamp Switch Malfunction.
2. Observe the scan tool Automatic Headlamp Disable Switch parameter while applying and releasing the automatic lamp control disable switch. The reading should toggle between Active and Inactive.
• If the reading does not change between the commanded states, refer to Headlamp Switch Malfunction.
3. Observe the scan tool Headlamps Flash Switch parameter while applying and releasing the flash to pass switch. The reading should toggle between Active and Inactive.
• If the reading does not change between the commanded states, refer to Turn Signal/Multifunction Switch Malfunction.
4. Observe the scan tool High Beam Select Switch parameter while applying and releasing the high beam select switch. The reading should toggle between Active and Inactive.
• If the reading does not change between the commanded states, refer to Turn Signal/Multifunction Switch Malfunction.
5. Command the Headlamp Low Beam Command ON and OFF with a scan tool. The low beam headlamps should turn ON and OFF when commanded.
• If the low beam headlamps do not turn ON and OFF when commanded, refer to Headlamps Malfunction - Low Beam.
6. Command the High Beam Headlamps ON and OFF with a scan tool. The high beam headlamps should turn ON and OFF when commanded.
• If the high beam headlamps do not turn ON and OFF when commanded, refer to Headlamps Malfunction - High Beam.
7. Command the All Indicators Test ON and OFF with a scan tool. The lights on indicator and high beam indicator should turn ON and OFF when changing between the commanded states.
• If the lights on indicator and high beam indicator illuminate during the test, replace the K9 BCM.
• If the lights on indicator and high beam indicator do not illuminate during the test or remain illuminated at all times, replace the P16 instrument cluster.
Circuit/System Testing
Warning
The high intensity discharge system produces high voltage and current. To reduce the risk of severe shocks and burns:
* Never open the high intensity discharge system ballast or the arc tube assembly starter.
* Never probe between the high intensity discharge system ballast output connector and the arc tube assembly.
Headlamp Switch Malfunction
1. Ignition OFF, disconnect the harness connectors at the S30 headlamp switch.
2. Ignition OFF, test for less than 5 ohm between the ground circuit terminal 6 and ground.
• If greater than the specified range, test the ground circuit for an open/high resistance.
3. Ignition ON, verify the scan tool Headlamp On Switch parameter is Inactive.
• If not the specified value, test the signal circuit terminal 4 for short to ground. If the circuit tests normal, replace the K9 BCM.
4. Verify the scan tool Automatic Headlamp Disable Switch parameter is Inactive.
• If not the specified value, test the signal circuit terminal 5 for short to ground. If the circuit tests normal, replace the K9 BCM.
5. Install a 3 A fused jumper wire between the signal circuit terminal 4 and ground. Verify the scan tool Headlamp On Switch parameter is Active.
• 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.
6. 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.
• 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.
7. If all circuits test normal, test or replace the S30 headlamp switch.
Turn Signal/Multifunction Switch Malfunction
1. Ignition OFF, disconnect the harness connector at the S78 turn signal/multifunction switch.
2. Ignition OFF, test for less than 5 ohm between the ground circuit terminal 3 and ground.
• If greater than the specified range, test the ground circuit for an open/high resistance.
3. Verify the scan tool Headlamps Flash Switch parameter is Inactive.
• 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.
4. Verify the scan tool High Beam Select Switch parameter is Inactive.
• 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.
5. 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.
• 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.
6. 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.
• 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.
7. If all circuits test normal, test or replace the S78 turn signal/multifunction switch.
Headlamps Malfunction - Low Beam
1. Ignition OFF, disconnect the harness connector at the appropriate E13 headlamp.
2. Ignition OFF, scan tool OFF, exterior lamps OFF, test for less than 5.0 ohm between the ground circuit terminal 2 and ground.
• If greater than the specified range, test the ground circuit for an open/high resistance.
3. Connect a test lamp between the control circuit terminal 1 and ground.
4. Command the Headlamp Low Beam Command ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
• 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.
• If the test lamp is always OFF, test the control circuit for a short to ground or open/high resistance. If the circuit tests normal, replace the K9 BCM.
5. If all circuits test normal, test or replace the E13 headlamp.
Headlamps Malfunction - High Beam
1. Ignition OFF, disconnect the X2 harness connector at the X50A underhood fuse block.
2. Connect a test lamp between the control circuit terminal 31 and B+.
3. Command the High Beam Headlamps ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
• If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the K9 BCM.
• If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K9 BCM.
4. Ignition OFF, connect the X2 harness connector at the X50A underhood fuse block. Disconnect the harness connector at the appropriate E13 Headlamp.
5. Test for less than 5 ohm between the ground circuit terminal 2 and ground.
• If greater than the specified range, test the ground circuit for an open/high resistance.
6. Connect a test lamp between the control circuit terminal 3 and ground.
7. Command the High Beam Headlamps ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
• If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the X50A underhood fuse block.
• 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 X50A underhood fuse block.
• 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, test or replace the E13 Headlamp.
8. If all circuits test normal, test or replace the E13 Headlamp.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Accessory Wiring Junction Block Retainer Replacement (Removal and Replacement)
* Headlamp, Instrument Panel Lamp Dimmer, and Fog Lamp Switch Replacement (Service and Repair)
* Headlamp Replacement (Headlamp Replacement)
* Turn Signal Multifunction Switch Replacement (Turn Signal Multifunction Switch Replacement)
* Control Module References (Programming and Relearning) for BCM or instrument cluster replacement, setup, and programming