When the ignition switch is turned to the ON position, the dash integration module (DIM) sends a class 2 message to the instrument panel integration module (IPM), the instrument cluster (IPC), the radio, and the cellular telephone docking station, if equipped via power moding. In response to this message, each module will turn on its vacuum fluorescent (VF) displays at maximum brightness. The IPM turns on the VF display for the heater and A/C control head.

When the park lamps are turned on, battery positive voltage (B+) is supplied to the dash integration module (DIM) dimming circuit via CKT 32 (YEL) from the rear junction block DIMR Fuse. The DIM also sends a class 2 message to the IPM, indicating that the park lamps are on. The IP dimmer switch in the headlamp switch is supplied a reference voltage (5 V) from the IPM via CKT 1688 (LT BLU/BLK). It is supplied a reference ground from the IPM via CKT 61 (YEL). The switch is a potentiometer that resistance varies as the switch is moved. The IPM receives an input voltage proportional to the resistance of the potentiometer via CKT 44 (DK GRN).

When the park lamps are on and it is dark outside, the IPM sends a class 2 message to the DIM, the IPC, the LH front door module (LFDM), the radio, and the cellular telephone docking station indicating that the VF displays and incandescent lamps should be dimmed and the dimming level. The IPM, the IPC, the radio, and the cellular telephone docking station all dim their VF displays to match the current dimming level. The DIM sends a pulse width modulated (PWM) signal to the IP and console incandescent switch backlighting at the dimming level indicated by the IP dimmer switch via CKT 1491 (YEL) or (YEL/BLK). The LFDM sends a simple bus interface (SBI) message to the RH front door module (RFDM), the LH rear door module (LRDM), and the RH rear door module (RRDM) indicating the dimming level. Each door module then sends a PWM signal to the incandescent switch backlighting in the respective door at the dimming level indicated by the IP dimmer switch via CKT 1491 (YEL) or (YEL/BLK).

When the IP dimmer switch is moved from MIN to MAX, all VF displays and incandescent switch backlighting dimming level changes from minimum intensity to maximum brightness in response to the IP dimmer switch.