Pinpoint Test B: All DIMMABLE Illumination Does Not Dim

WARNING: This page is about a different car, the 2010 Lincoln MKX and 2010 Ford Edge. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.

NOTE: Calibrate the instrument panel dimmer switch by rotating the dimmer switch from the full dim position to the DOME LAMP position before continuing diagnostics.

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.
  Refer to COMPONENT TESTING for component testing.
- 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 . TEST the system for normal operation.
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.
  
  Fig 1: Checking Circuit VLN18 For Short To Voltage
  Courtesy of FORD MOTOR CO.
- 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 .
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 CLN27 (WH/BN), harness side and ground.
  
  Fig 2: Checking Circuit CLN27 For Short To Voltage
  Courtesy of FORD MOTOR CO.
- Is any voltage present?
- Yes: REPAIR circuit CLN27 (WH/BN) for a short to voltage. CLEAR the DTCs. REPEAT the self-test.
- No: GO to B4 .
B4 CHECK THE INSTRUMENT PANEL DIMMER SWITCH INPUT CIRCUIT FOR A SHORT TO GROUND
- Measure the resistance between the instrument panel dimmer switch C2298-1, circuit VLN18 (BU/WH), harness side and ground.
  
  Fig 3: Checking Circuit VLN18 For Short To Ground
  Courtesy of FORD MOTOR CO.
- Is the resistance greater than 10,000 ohms?
- Yes: GO to B5 .
- No: REPAIR circuit VLN18 (BU/WH) for a short to ground. TEST the system for normal operation.
B5 CHECK THE INSTRUMENT PANEL DIMMER SWITCH INPUT CIRCUIT FOR AN OPEN
- 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.
  
  Fig 4: Checking Circuit VLN18 For An Open
  Courtesy of FORD MOTOR CO.
- Is the resistance less than 5 ohms?
- Yes: GO to B6 .
- No: REPAIR circuit VLN18 (BU/WH) for an open. CLEAR the DTCs. REPEAT the self-test.
B6 CHECK THE INSTRUMENT PANEL DIMMER SWITCH RETURN CIRCUIT FOR AN OPEN
- Ignition OFF.
- Measure the resistance between the instrument panel dimmer switch C2298-4, circuit CLN27 (WH/BN), harness side and the SJB C2280b-33, circuit CLN27 (WH/BN), harness side.
  
  Fig 5: Checking Circuit CLN27 For An Open
  Courtesy of FORD MOTOR CO.
- Is the resistance less than 5 ohms?
- Yes: GO to B7 .
- No: REPAIR circuit CLN27 (WH/BN) for an open. CLEAR the DTCs. REPEAT the self-test.
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 . REFER to MULTIFUNCTION ELECTRONIC MODULES . 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.