Test B: The Instrument Panel Illumination Does Not Dim

PINPOINT TEST B: THE INSTRUMENT PANEL ILLUMINATION DOES NOT DIM

B1-B4:

B4-B7:

Normal Operation
With the parking lamps on, 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 resistor 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.

DTC B1247 - sets when the illumination dimmer switch detects a open circuit from the SJB circuitry.

DTC B2132 - sets when the illumination dimmer switch detects a short to the reference signal or a short to ground.

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