Pinpoint Test D: The Headlamps Are On Continuously
Headlamps
Pinpoint Test D: The Headlamps Are On Continuously
Refer to Wiring Diagram Set 85, Headlamps/Autolamps for schematic and connector information. Diagrams By Number
Normal Operation
The Lighting Control Module (LCM) sends voltage signals to the headlamp switch through circuits 1400 (TN/WH), 1032 (WH/BK) and 1033 (RD/YE). The headlamp switch always routes one of the signal circuits to ground through circuit 57 (BK) for any given headlamp switch position. If the LCM detects a fault with the headlamp switch input, the LCM defaults the exterior lamps on.
When the LCM detects the headlamp switch in the HEADLAMPS ON position and the multifunction switch in the LOW BEAM position, the LCM provides voltage through circuits 160 (DB/WH) and 161 (DG/OG) to the LH and RH low beam headlamps, respectively.
The LCM sends a 5 volt reference signal to the multifunction switch through circuit 12 (LG/BK). When the multifunction switch is placed in the HIGH BEAM position, the voltage signal is routed to ground, puling the signal low. When the multifunction switch is placed in the FLASH-TO-PASS position, battery voltage is routed through circuit 12 (LG/BK) to the LCM pulling the signal high. When the LCM detects a request for the flash-to-pass or high beam headlamps, the LCM provides voltage to the high beam headlamps.
When the LCM detects the headlamp switch in the HEADLAMPS ON position and the multifunction switch in the HIGH BEAM or FLASH-TO-PASS position, the LCM provides voltage through circuits 1337 (VT/YE) and 1335 (YE/WH) to the LH and RH high beam headlamps, respectively.
When the LCM detects the wipers are on for a predetermined amount of time, the LCM provides voltage to the exterior lamps.
- DTC B1472 (Lamp Headlamp Input Circuit Short to Ground) - an on-demand DTC that sets when the LCM detects a short to ground from the headlamps on input circuit.
- DTC B1570 (Lamp Headlamp High-Beam Circuit Short to Ground) - an on-demand DTC that sets when the LCM detects a short to ground from the high beam request input circuit.
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- Headlamp switch
- Multifunction switch
- Wig-wag module
- LCM
PINPOINT TEST D: THE HEADLAMPS ARE ON CONTINUOUSLY
NOTICE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.
NOTE: Failure to disconnect the battery when instructed will result in false resistance readings. Refer to Battery.
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D1 DETERMINE IF THE HIGH BEAMS ARE ILLUMINATED
- Ignition OFF.
- Place the headlamp switch in the HEADLAMPS ON position.
- Place the multifunction switch in the FLASH-TO-PASS position while observing the headlamps.
- Does the headlamp brightness increase?
Yes
GO to D7.
No
GO to D2.
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D2 CHECK THE MULTIFUNCTION SWITCH
- Disconnect: Multifunction Switch C202c.
- Do the high beam headlamps continue to illuminate?
Yes
GO to D3.
No
INSTALL a new multifunction switch. CLEAR the DTCs. REPEAT the self-test.
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D3 CHECK CIRCUITS 1337 (VT/YE) AND 1335 (YE/WH) FOR A SHORT TO VOLTAGE
- Ignition OFF.
- Disconnect: LCM C2145c.
- Ignition ON.
- Do the high beam headlamps continue to illuminate?
Yes
For police vehicles, GO to D4.
For all others, REPAIR circuit 1337 (VT/YE) (LH high beam) or circuit 1335 (YE/WH) (RH high beam) for a short to voltage. TEST the system for normal operation.
No
GO to D5.
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D4 CHECK CIRCUITS 1337 (VT/YE) AND 1335 (YE/WH) FOR A SHORT TO VOLTAGE (POLICE VEHICLES)
- Ignition OFF.
- Disconnect: Wig-Wag Module C1352 or C1365.
- Ignition ON.
- Do the high beam headlamps continue to illuminate?
Yes
REPAIR circuit 1337 (VT/YE) (LH high beam) or circuit 1335 (YE/WH) (RH high beam) for a short to voltage. TEST the system for normal operation.
No
INSTALL a new wig-wag module. CLEAR the DTCs. REPEAT the self-test.
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D5 CHECK CIRCUIT 12 (LG/BK) FOR A SHORT TO VOLTAGE
- Place the headlamp switch in the OFF position.
- Ignition OFF.
- Disconnect: LCM C2145d.
- Ignition ON.
- Measure the voltage between the multifunction switch C202c-10, circuit 12 (LG/BK), harness side and ground.
- Is any voltage present?
Yes
REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test.
No
GO to D6.
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D6 CHECK CIRCUIT 12 (LG/BK) FOR A SHORT TO GROUND
- Ignition OFF.
- Measure the resistance between the multifunction switch C202c-10, circuit 12 (LG/BK), harness side and ground.
- Is the resistance greater than 10,000 ohms?
Yes
GO to D14.
No
REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test.
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D7 CHECK FOR AUTOLAMP SYSTEM DTCs
- Review the DTCs retrieved from the LCM self-test.
- Was DTC B1449 or B1696 retrieved?
Yes
REFER to Autolamps.
No
GO to D8.
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D8 CHECK THE LCM HEADLAMP SWITCH PIDs
- Place the headlamp switch in the OFF position.
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: LCM DataLogger.
- Monitor the LCM headlamp switch status PIDs (HLMPOFF, PARK_SW, HD_LMP_SW) while moving the headlamp switch through all positions.
- Do the headlamp switch PIDs agree with the headlamp switch position?
Yes
GO to D9.
No
GO to D10.
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D9 CHECK CIRCUITS 160 (DB/WH) AND 161 (DG/OG) FOR A SHORT TO VOLTAGE
- Ignition OFF.
- Disconnect: LCM C2145c and C2145d.
- Ignition ON.
- Do the low beam headlamps continue to illuminate?
Yes
REPAIR circuit 160 (DB/WH) (LH low beam) or circuit 161 (DG/OG) (RH low beam). CLEAR the DTCs. REPEAT the self-test.
No
GO to D14.
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D10 CHECK THE HEADLAMP SWITCH
- Ignition OFF.
- Disconnect: Headlamp Switch C205a.
- Carry out the headlamp switch component test.
- Is the headlamp switch OK?
Yes
GO to D11.
No
INSTALL a new headlamp switch. REFER to Headlamp Switch Service and Repair. CLEAR the DTCs. REPEAT the self-test.
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D11 CHECK CIRCUIT 57 (BK) FOR AN OPEN
- Ignition OFF.
- Disconnect: Negative Battery Cable.
- Disconnect: Headlamp Switch C205a.
- Measure the resistance between the headlamp switch C205a-7, circuit 57 (BK), harness side and ground.
- Is the resistance less than 5 ohms?
Yes
GO to D12.
No
REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test.
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D12 CHECK THE HEADLAMP SWITCH INPUT CIRCUITS FOR AN OPEN
- Disconnect: LCM C2145a and C2145b.
- Measure the resistance between the headlamp switch, harness side and the LCM, harness side as follows:
- Are the resistances less than 5 ohms?
Yes
GO to D13.
No
REPAIR the circuit in question. CLEAR the DTCs. REPEAT the self-test.
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D13 CHECK CIRCUIT 1033 (RD/YE) FOR A SHORT TO GROUND
- Measure the resistance between the headlamp switch C205a-10, circuit 1033 (RD/YE), harness side and ground.
- Is the resistance greater than 10,000 ohms?
Yes
GO to D14.
No
REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test.
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D14 CHECK FOR CORRECT LCM OPERATION
- Ignition OFF.
- Disconnect all the LCM connectors.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect all the LCM connectors and make sure they seat correctly.
- Operate the system and verify the concern is still present.
- Is the concern still present?
Yes
INSTALL a new LCM. TEST the system for normal operation.
No
The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. CLEAR the DTCs. REPEAT the self-test.
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