Test B: The Instrument Panel Illumination Does Not Dim

PINPOINT TEST B: THE INSTRUMENT PANEL ILLUMINATION DOES NOT DIM

B1-B3:

B3-B4:

B5-B8:

Normal Operation
When the parking lamp switch is placed in the PARK or headlamps ON position, a voltage signal is supplied to the instrument panel dimmer switch through circuit 1036 (BN/WH) from the smart junction box (SJB). The dimmer switch passes this voltage through a variable resister and then returns the signal to the SJB on circuit 1035 (OG/RD). The SJB uses the return signal to determine the backlighting intensity desired by the operator. A pulse width modulated (PWM) signal is sent from the SJB to each of the dimmable backlights, maintaining the operators desired level of lighting intensity.

The dimmable backlighting defaults to full intensity if the instrument panel dimmer switch or circuitry fails.

Possible Causes
- circuit 1035 (OG/RD) open, short to ground, or short to voltage
- circuit 1036 (BN/WH) open or short to ground
- circuit 1405 (LB/BK) short to voltage
- instrument panel dimmer switch
- SJB