When the headlamp switch is placed in the ON position, the dash integration module (DIM) headlamp switch input circuit is grounded via the headlamp switch ground circuit.

The twilight delay switch in the headlamp switch is supplied a reference voltage and a reference ground from the instrument panel integration module. The switch is a potentiometer that varies resistance as the switch is moved. The IPM receives an input voltage proportional to the resistance of the potentiometer via twilight delay input circuit. The IPM sends a class 2 message to the dash integration module (DIM) indicating the on/off status and delay length for the twilight sentinel. With the twilight sentinel in an ON position, the DIM will automatically control the headlamps on/off status depending on the nighttime/daytime status of the ambient light sensor. The DIM will use the twilight sentinel delay length to know how long to keep the headlamps and park lamps on after the ignition switch transitions from ON to OFF during nighttime conditions.

The dash integration module (DIM) supplies battery positive voltage (B+) to the HDLP LO BM relay coil when the headlamps or park lamps need to be on or when the ignition switch is in the ON position. Battery positive voltage (B+) is always supplied to the HDLP LO BM relay switch through the underhood fuse block. When the headlamps are to be active, the DIM supplies ground to the low/high beam switch in the headlamp dimmer switch. With the headlamp dimmer switch in the low beam position, the HDLP LO BM relay coil is grounded. The coil is energized, closing the switch contacts. This supplies battery positive voltage (B+) to the HDLOBML Fuse and HDLOBMR Fuse. HDLOBML Fuse supplies battery positive voltage (B+) to the LH low beam headlamp. HDLOBMR Fuse supplies battery positive voltage (B+) to the RH low beam headlamp. The LH and RH low beam headlamps are both permanently grounded, so both low beam headlamps have power and ground, and then light.

The dash integration module (DIM) supplies battery positive voltage (B+) to the HDLP HI BM relay coil when the headlamps or park lamps need to be on or when the ignition switch is in ON position. Battery positive voltage (B+) is always supplied to the HDLP HI BM relay switch through the underhood fuse block. When the low beam headlamps are on as described above and then the headlamp dimmer switch is placed in the high beam position, the HDLP HI BM relay coil is grounded. The coil is energized, closing the switch contacts. This supplies battery positive voltage (B+) to the HDHIBML Fuse and HDHIBMR Fuse. HDHIBML Fuse supplies battery positive voltage (B+) to the LH high beam headlamp. HDHIBMR Fuse supplies battery positive voltage (B+) to the RH high beam headlamp. The LH and RH high beam headlamps are both permanently grounded, so both high beam headlamps have power and ground, and then light.

When the headlamps are to be active, the DIM supplies ground to the HDLP LO BM relay coil and the low/high beam switch in the headlamp dimmer switch. The relay acts as described above and the low beam headlamps light. When the headlamp dimmer switch is in the high beam position, the HDLP HI BM relay coil is grounded. The relay acts as described above and the high beam headlamps light in addition to the low beam headlamps.

The flash-to-pass switch is permanently grounded. When the headlamp dimmer switch is pulled toward driver, the flash-to-pass switch in the headlamp dimmer switch closes, and the DIM Flash-To-Pass input is grounded. In response to this input, the DIM supplies ground to the HDLP HI BM relay coil. The HDLP HI BM relay has battery positive voltage (B+) as described above. The relay is energized closing the switch contacts. The high beam headlamps are supplied battery positive voltage (B+) as described above. If the low beam headlamps are already on, they will remain on during flash-to-pass. The high beam headlamps will only remain on as long as the switch is held.

The ambient light sensor is supplied a reference ground from the instrument panel integration module (IPM). The sensor is a light sensitive variable resistor that varies resistance as the outside ambient light level changes. The IPM receives an input voltage proportional to the resistance of the resistor. The IPM sends a Class 2 message to the dash integration module (DIM) and the rear integration module (RIM) indicating the daytime/nighttime status. The DIM uses the daytime/nighttime status of the ambient light sensor to automatically turn on and off the headlamps with the twilight sentinel on. The RIM uses the daytime/nighttime status of the ambient light sensor to automatically turn on and off the interior courtesy lamps with the interior lamp switch in the AUTO position.

With the daytime running lamps (DRL) programmed to be on, the DRL will operate when the ignition switch is in the ON position, the gear selector lever is out of the PARK position, the headlamp switch is in the OFF position, and the ambient light sensor indicates daytime conditions. The DRL will remain on at night if the twilight sentinel switch is in the OFF position, and the headlamp switch is in the OFF position. Battery positive voltage (B+) is supplied to the DRL relay coil through the underhood fuse block. Battery positive voltage is supplied through the underhood fuse block FOG/DRL Fuse to the DRL relay normally open switch. When the dash integration module (DIM) determines that conditions are right for the DRL, the DIM grounds the DRL relay coil. This energizes the DRL relay coil and closes the switch. Battery positive voltage (B+) is supplied through the DRL resistor to the LH and RH low beam headlamps.

The high beam indicator may be ON during any power mode except for START. The IPC illuminates the high beam indicator when the dash integration module (DIM) sends a class 2 serial data message indicating that the high beam headlamps are ON.