Pinpoint Test B: All Dimmable Switch Illumination Is Inoperative

Instrument Cluster and Panel Illumination

Pinpoint Test B: All Dimmable Switch Illumination Is Inoperative

Refer to Wiring Diagram Set 71, Cluster and Panel Illumination for schematic and connector information. Diagrams By Number

Normal Operation

The Lighting Control Module (LCM) receives voltage from the Central Junction Box (CJB). With the parking lamps on, the LCM generates a Pulse Width Modulated (PWM) voltage which is distributed to the dimmable components. Light intensity is adjusted by rotating the instrument panel dimmer switch.

This pinpoint test is intended to diagnose the following:

- Fuse
- Wiring, terminals or connectors
- LCM


PINPOINT TEST B: ALL DIMMABLE SWITCH ILLUMINATION IS INOPERATIVE

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, Mounting and Cables Battery Disconnect.

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B1 CHECK THE LCM VOLTAGE SUPPLY CIRCUIT FOR AN OPEN


- Ignition OFF.
- Disconnect: LCM C2145c.
- Ignition ON.
- Measure the voltage between the LCM C2145c-17, circuit 905 (GY/LB), harness side and ground.




- Is the voltage greater than 10 volts?

Yes
GO to B2.

No
VERIFY the CJB fuse 21 (10A) is OK. If OK, REPAIR circuit 905 (GY/LB) for an open. TEST the system for normal operation. If not OK, REFER to the Wiring Diagrams to identify the possible causes of the circuit short. Diagrams By Number

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B2 CHECK THE CLUSTER AND PANEL ILLUMINATION INPUT CIRCUIT FOR AN OPEN OR SHORT TO GROUND


- NOTE: If the fuse fails, refer to the Wiring Diagrams to isolate the cause of the circuit short. Diagrams By Number
- Connect a fused jumper wire between the LCM C2145c-17, circuit 905 (GY/LB), harness side and the LCM C2145c-3, circuit 484 (OG/BK), harness side.




- Do the instrument panel lamps illuminate?

Yes
REMOVE the jumper wire. GO to B3.

No
REMOVE the jumper wire. REPAIR circuit 484 (OG/BK) for an open. TEST the system for normal operation.

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B3 CHECK THE LCM GROUND CIRCUIT FOR AN OPEN


- Ignition OFF.
- Disconnect: Negative Battery Cable.
- Disconnect: LCM C2145a.
- Measure the resistance between the LCM C2145a-11, circuit 676 (PK/OG), harness side and ground; and between the LCM C2145c-7, circuit 676 (PK/OG), harness side and ground.




- Are the resistances less than 5 ohms?

Yes
GO to B4.

No
REPAIR circuit 676 (PK/OG) for an open. TEST the system for normal operation.

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B4 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 Lighting Control Module (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.

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