Pinpoint Test B: All Dimmable Illumination Does Not Dim
Instrument Cluster and Panel Illumination
Pinpoint Tests
Pinpoint Test B: All Dimmable Illumination Does Not Dim
Refer to Wiring Diagram Set 71, Cluster and Panel Illumination for schematic and connector information. Diagrams By Number
Normal Operation
The Smart Junction Box (SJB) sends a voltage reference signal to the instrument panel dimmer switch through circuit VLN18 (BU/WH). The signal is routed through a variable resistor within the instrument panel dimmer switch and then back to the SJB through circuit RLN29 (WH/OG) to an internal ground. The reference voltage changes depending on the position of the dimmer switch. When the dimmer switch is in the lowest setting, the resistance is low. When the SJB senses the voltage is low (switch in the lowest setting), the dimmable backlighting intensity is low. When the SJB senses the voltage reference is high (switch in the highest setting), the dimmable backlighting intensity is bright. If the signal is too high (an open circuit or short to voltage), the SJB faults the dimmable backlighting to full nighttime brightness. If circuit VLN18 (BU/WH) is short to ground, the SJB interprets this as the lowest setting and sets the backlighting to the lowest intensity level, appearing to be inoperative.
Based on input received from the instrument panel dimmer switch, the SJB sends a message over the network to the backlit modules indicating the backlighting intensity level and a Pulse Width Modulated (PWM) voltage to the hardwired dimmable illumination sources through circuit VLN04 (VT/GY).
The SJB also sends a message over the Controller Area Network (CAN) to the Audio Control Module (ACM) (vehicles with navigation), the Trailer Brake Control (TBC) module and the Instrument Cluster (IC) to indicate the backlighting intensity level. If the receiving module receives invalid backlighting data from the SJB for 5 seconds or less, the receiving module defaults the backlighting to the last setting.
If the receiving module does not receive the backlighting status message from the SJB or if the data received is deemed invalid for more than 5 seconds, the receiving module sets a communication message related DTC in continuous memory and defaults the backlighting to full nighttime intensity.
- DTC B2212 (Panel Dim Switch Out of Range) - an on-demand DTC that sets when the SJB detects an open or short to voltage from the dimmer switch input switch circuit.
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- Instrument panel dimmer switch
- SJB
PINPOINT TEST B: ALL DIMMABLE ILLUMINATION DOES NOT DIM
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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B1 CHECK THE INSTRUMENT PANEL DIMMER SWITCH
- Ignition OFF.
- Disconnect: Instrument Panel Dimmer Switch C2298.
- Carry out the component test for the instrument panel dimmer switch.
- Is the instrument panel dimmer switch OK?
Yes
GO to B2.
No
INSTALL a new instrument panel dimmer switch. REFER to Instrument Panel Dimmer Switch Service and Repair. CLEAR the DTCs. REPEAT the self-test.
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B2 CHECK THE INSTRUMENT PANEL DIMMER SWITCH INPUT CIRCUIT FOR A SHORT TO VOLTAGE
- Disconnect: SJB C2280b.
- Ignition ON.
- Measure the voltage between the instrument panel dimmer switch C2298-1, circuit VLN18 (BU/WH), harness side and ground.
- Is any voltage present?
Yes
REPAIR circuit VLN18 (BU/WH) for a short to voltage. CLEAR the DTCs. REPEAT the self-test.
No
GO to B3.
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B3 CHECK THE INSTRUMENT PANEL DIMMER SWITCH RETURN CIRCUIT FOR A SHORT TO VOLTAGE
- Measure the voltage between the instrument panel dimmer switch C2298-4, circuit RLN29 (WH/OG), harness side and ground.
- Is any voltage present?
Yes
REPAIR circuit RLN29 (WH/OG) for a short to voltage. CLEAR the DTCs. REPEAT the self-test.
No
GO to B4.
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B4 CHECK THE INSTRUMENT PANEL DIMMER SWITCH INPUT CIRCUIT FOR AN OPEN
- Ignition OFF.
- Measure the resistance between the instrument panel dimmer switch C2298-1, circuit VLN18 (BU/WH), harness side and the SJB C2280b-34, circuit VLN18 (BU/WH), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to B5.
No
REPAIR circuit VLN18 (BU/WH) for an open. CLEAR the DTCs. REPEAT the self-test.
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B5 CHECK THE INSTRUMENT PANEL DIMMER SWITCH RETURN CIRCUIT FOR AN OPEN
- Measure the resistance between the instrument panel dimmer switch C2298-4, circuit RLN29 (WH/OG), harness side and the SJB C2280b-33, circuit RLN29 (WH/OG), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to B6.
No
REPAIR circuit RLN29 (WH/OG) for an open. CLEAR the DTCs. REPEAT the self-test.
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B6 CHECK THE INSTRUMENT PANEL DIMMER SWITCH INPUT CIRCUIT FOR A SHORT TO GROUND
- Disconnect: SJB C2280b.
- Measure the resistance between the instrument panel dimmer switch C2298-1, circuit VLN18 (BU/WH), harness side and ground.
- Is the resistance greater than 10,000 ohms?
Yes
GO to B7.
No
REPAIR circuit VLN18 (BU/WH) for a short to ground. TEST the system for normal operation.
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B7 CHECK FOR CORRECT SJB OPERATION
- Disconnect all the SJB connectors.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect all the SJB 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 SJB. 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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