Headlamps Malfunction - Low Beam (With TT6, TT7, or TT8)
Headlamps Malfunction - Low Beam (With TT6, TT7, or TT8)
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
The body control module (BCM) monitors the 12 V signal circuits for the headlamps off signal, headlamps on signal and the park lamp on signal circuits. When the headlight control switch is selected to the desired headlamp function, the signal circuit is pulled to ground and the BCM will detect the voltage drop in that signal circuit and will command the appropriate lights to turn on or turn off.
When the headlight switch is placed in low beam position, the body control module (BCM) energizes the low beam headlamp relay which supplies battery voltage to the respective headlamp control circuits.
Diagnostic Aids
The following symptoms are noticeable signs of bulb failure:
* Flickering light, caused in the early stages of bulb failure.
* Lights go out, caused when the ballast detects excessive, repetitive bulb re-strike.
* Color change-The lamp may change to a dim pink glow.
Reference Information
Schematic Reference
Headlights/Daytime Running Lights (DRL) Schematics (Headlights/Daytime Running Lights (DRL) 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 Headlamps On Switch, Park Lamps Switch and Automatic Headlamps Disable Switch parameters while selecting the headlamp control switch between the Off, park lamps and headlamps settings. Each parameter should be Inactive and change to Active as each setting is selected.
• If the values do not change, refer to Headlamp Switch Malfunction
2. Command the Headlamp Low Beam ON and OFF with a scan tool. The E4G headlamp-left low beam and the E4H headlamp-right low beam should turn ON and OFF when changing between the commanded states
• If the E4G headlamp-left low beam and the E4H headlamp-right low beam are always ON or always OFF, refer to Low Beam Headlamps Malfunction
Circuit/System Testing
Headlamp Switch Malfunction
1. Ignition OFF, disconnect the X1 harness connector at the S30 headlamp switch.
2. Ignition OFF, test for less than 30 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 Park Lamps Switch parameter is Inactive.
• 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.
4. 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.
• 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.
5. Verify the scan tool Headlamps On 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.
6. 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.
• 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. Verify the scan tool Automatic Headlamps Disable Switch parameter is Inactive.
• 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.
8. 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.
• 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.
9. If all circuits test normal, test or replace the S30 headlamp switch.
Low Beam Headlamps Malfunction
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.
1. Ignition OFF, disconnect the KR49 headlamp low beam relay.
2. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 30 and ground.
• If the test lamp illuminates, test the control circuit for a short to voltage.
3. Verify that a test lamp illuminates between the B+ circuit terminal 87 and ground.
• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance
4. Verify that a test lamp illuminates between the B+ circuit terminal 86 and ground.
• If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.
5. Connect a 20A fused jumper wire between the B+ circuit terminal 87 and the control circuit terminal 30. Verify the E4G headlamp-left low beam and the E4H headlamp-right low beam are activated.
• If the E4G headlamp-left low beam or the E4H headlamp-right low beam do not activate, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the appropriate E4 headlamp- low beam
6. Connect a test lamp between the B+ circuit terminal 86 and the control circuit terminal 85.
7. Ignition ON, command the Low Beam Lamps 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.
8. If all circuits test normal, test or replace the KR49 headlamp low beam relay.
Component Testing
Relay Test
1. Ignition OFF, disconnect the KR49 headlamp low beam relay.
2. Test for 60-180 ohm between terminals 85 and 86.
• If not within the specified range, replace the KR49 headlamp low beam relay.
3. Test for infinite resistance between the following terminals:
* 30 and 86
* 30 and 87
* 30 and 85
* 85 and 87
• If not the specified value, replace the KR49 headlamp low beam relay.
4. Install a 15A fused jumper wire between relay terminal 85 and 12 V. Install a jumper wire between relay terminal 86 and ground. Test for less than 2 ohm between terminals 30 and 87.
• If greater than the specified range, replace the KR49 headlamp low beam relay.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Headlamp Replacement (Headlamp Replacement)
* Headlamp Ballast Replacement (TT6, TT7, TT8) (Headlamp Ballast Replacement (TT6, TT7, TT8))
* Headlamp Capsule Replacement (TT6, TT7, TT8) (Headlamp Capsule Replacement (TT6, TT7, TT8))
* Relay Replacement (Attached to Wire Harness) (Relay Replacement (Attached to Wire Harness))Relay Replacement (Within an Electrical Center) (Relay Replacement (Within an Electrical Center))
* Headlamp Switch Replacement (Service and Repair)
* Control Module References (Programming and Relearning) for BCM replacement, programming and setup