Pinpoint Test T: The Fog Lamps Are On Continuously
Fog Lamps
Pinpoint Tests
Pinpoint Test T: The Fog Lamps Are On Continuously
Refer to Wiring Diagram Set 86, Fog Lamps for schematic and connector information. Diagrams By Number
Normal Operation
The Lighting Control Module (LCM) sends a voltage reference signal to the headlamp switch. When the fog lamp switch is engaged, the signal is routed to ground. When a request for the fog lamps is detected (and the exterior lamps are on), the LCM provides voltage to the fog lamp relay coil, energizing the fog lamp relay. When the fog lamp relay is energized, voltage is routed to the fog lamps.
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- Fog lamp relay
- Headlamp switch
- LCM
PINPOINT TEST T: THE FOG LAMPS 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.
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T1 MONITOR THE LCM HEADLAMP SWITCH PID
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: LCM DataLogger.
- NOTE: Make sure the headlamp switch is in the OFF position.
- Monitor the LCM headlamp switch status PID (HD_LMP_SW).
- Does the headlamp switch PID indicate the fog lamp switch is active?
Yes
GO to T5.
No
GO to T2.
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T2 CHECK THE FOG LAMP RELAY OUTPUT CIRCUIT FOR A SHORT TO VOLTAGE
- Ignition OFF.
- Disconnect: Fog Lamp Relay.
- Ignition ON.
- Do the fog lamps continue to illuminate?
Yes
REPAIR circuit 478 (TN/OG) for a short to voltage. TEST the system for normal operation.
No
GO to T3.
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T3 CHECK THE FOG LAMP RELAY
- Ignition OFF.
- Carry out the fog lamp relay component test.
- Is the fog lamp relay OK?
Yes
GO to T4.
No
INSTALL a new fog lamp relay. TEST the system for normal operation.
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T4 CHECK THE FOG LAMP RELAY COIL CIRCUIT FOR A SHORT TO VOLTAGE
- Disconnect: LCM C2145a.
- Ignition ON.
- Measure the voltage between the fog lamp relay pin 1, circuit 1347 (DB/WH), BJB face side and ground.
- Is any voltage present?
Yes
REPAIR circuit 1347 (DB/WH) for a short to voltage. TEST the system for normal operation.
No
GO to T7.
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T5 CHECK THE INPUT TO THE LCM
- Measure the resistance between the LCM C2145b-11, circuit 477 (LB/BK), harness side and ground.
- Is the resistance greater than 10,000 ohms?
Yes
GO to T7.
No
GO to T6.
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T6 CHECK THE FOG LAMP REQUEST INPUT CIRCUIT FOR A SHORT TO GROUND
- Ignition OFF.
- Disconnect: LCM C2145b.
- Disconnect: Headlamp Switch C205a.
- Measure the resistance between the LCM C2145b-11, circuit 477 (LB/BK), harness side and ground.
- Is the resistance greater than 10,000 ohms?
Yes
INSTALL a new headlamp switch. REFER to Headlamp Switch Service and Repair. TEST the system for normal operation.
No
REPAIR circuit 477 (LB/BK) for a short to ground. TEST the system for normal operation.
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T7 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. REFER to Body Control Systems. 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.
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