Test A: The Control Illumination Is Inoperative

PINPOINT TEST A: THE CONTROL ILLUMINATION IS INOPERATIVE

A1-A2:

Normal Operation
When the parking lamps or the headlamps are ON, the smart junction box (SJB) sends a voltage signal to the instrument panel dimmer switch on circuit VLN18 (BU/WH) and monitors a return voltage from the instrument panel dimmer switch on circuit CLN27 (WH/BN). By comparing the difference between the 2 voltage signals, the SJB determines the intensity of the backlighting desired by the operator. The SJB sends a pulse-width modulated (PWM) voltage to the dimmable illumination sources on circuit VLN04 (VT/GY) based on the input received from the instrument panel dimmer switch. The SJB also sends a message over the medium speed controller area network (CAN) to the electronic automatic temperature control (EATC) (if equipped), the audio unit and the instrument cluster to indicate the backlighting intensity level.

Possible Causes
- SJB