Test C

PINPOINT TEST C: THE CONTROL ILLUMINATION IS ALWAYS ON

Test C1:

Test C2-C7:

Normal Operation
The headlamp switch supplies the instrument cluster with the headlamp switch position status. The instrument panel dimmer switch provides the instrument cluster with the dimming control status through signal circuit 8-LE10 (WH/BK) and return circuit 9-LE10 (BN/YE). The instrument cluster sends the illumination message to the front electronic module (FEM) over the standard corporate protocol (SCP) communication network, circuits 4-EG8 (GY/VT) and 5-EG8 (BU/WH), based upon the instrument panel dimmer switch position. The FEM is supplied with illumination power through circuit 29S-DK22 (OG/YE) whenever the switched system power (SSP) is energized. When the headlamp switch is in the PARK, HEADLAMP, or AUTOLAMP ON position, the instrument cluster sends the FEM an illumination message and the FEM, in turn, provides a pulse width modulation (PWM) power to the interior auxiliary junction box through circuit 64S-LH2 (BU/RD) and then to the dimmable backlighting sources through circuits 64S-LK21 (BU/BK) and 64S-LK1 (LB). Circuit 64S-LK1 (LB) is then spliced and sent to the dimmable backlighting sub-sources through circuits 64-LK18 (BU/RD), 64S-LE10 (BU/YE), 64S-LH26 (BU/BK), 64S-LH45 (BU/OG), and 64S-LK29 (BU/RD). For the fixed backlighting system, when the key is in the ON position, the auxiliary junction box sends the rear electronic module (REM) a voltage signal through circuit 29S-DK31 (OG/BK). The REM, in turn, sends B+ voltage to the fixed backlighting sources through circuit 7-LH1 (YE) for 100% illumination density.

Possible Causes
- circuit 7-LH1 (YE) short to power
- circuit 64S-LK1 (LB) short to power
- circuit 64S-LK21 (BU/BK) short to power
- circuit 64S-LH2 (BU/RD) short to power
- auxiliary junction box
- front electronic module (FEM)
- rear electronic module (REM)