Pinpoint Test I: The Courtesy Lamps Are Inoperative - From The Instrument Panel Dimmer Switch
WARNING: This page is about a different car, the 2010 Lincoln Town Car. However, it is still accessible from the selected car via links, so may be relevant.
Refer to appropriate SYSTEM WIRING DIAGRAMS article, Interior Lamps for schematic and connector information.
Normal Operation
The lighting control module (LCM) monitors the headlamp switch status on circuit 1034 (BK/WH) to determine if the courtesy lamps are requested. Based on the headlamp switch status, the LCM energizes the courtesy lamps through circuit 53 (BK/LB).
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- Instrument panel dimmer switch
- LCM
PINPOINT TEST I: THE COURTESY LAMPS ARE INOPERATIVE - FROM THE INSTRUMENT PANEL DIMMER SWITCH
NOTE:
Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.
- I1 CHECK THE INSTRUMENT PANEL DIMMER SWITCH
- Key in OFF position.
- Disconnect: Instrument Panel Dimmer Switch C205b
- Connect a fused (15A) jumper wire between the instrument panel dimmer switch C205b-5, circuit 1034 (BK/WH), harness side and the instrument panel dimmer switch C205b-4, circuit 57 (BK), harness side.
- Do the courtesy lamps illuminate?
- YES : REMOVE the jumper wire. INSTALL a new instrument panel dimmer switch. REFER to INSTRUMENT CLUSTER & PANEL ILLUMINATION article. TEST the system for normal operation.
- NO : REMOVE the jumper wire. Go to I2.
- I2 CHECK CIRCUIT 57 (BK) FOR AN OPEN
- Measure the resistance between the instrument panel dimmer switch C205b-4, circuit 57 (BK), harness side and ground.
- Is the resistance less than 5 ohms?
- YES : Go to I3.
- NO : REPAIR the circuit. TEST the system for normal operation.
- I3 CHECK CIRCUIT 1034 (BK/WH) FOR AN OPEN
- Disconnect: LCM C2145b
- Measure the resistance between the LCM C2145b-3, circuit 1034 (BK/WH), harness side and the instrument panel dimmer switch C205b-5, circuit 1034 (BK/WH), harness side.
- Is the resistance less than 5 ohms?
- YES : Go to I4.
- NO : REPAIR the circuit. TEST the system for normal operation.
- I4 CHECK FOR CORRECT LCM OPERATION
- 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 MULTIFUNCTION ELECTRONIC MODULES article. 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.