When the headlamp switch is placed in the ON position, the dash integration module (DIM) Headlamp Switch input is grounded via CKT 103 (WHT). When the headlamp switch is placed in the AUTO position, the instrument panel integration module (IPM) receives an input via CKT 1783 (PPL). The IPM sends a class 2 message to the DIM indicating that the headlamp switch is in the AUTO position. In response to the message, the DIM will automatically control the headlamps on/off status depending on the nighttime/daytime status of the ambient light sensor.

The dash integration module (DIM) supplies battery positive voltage (B+) via CKT 1483 (DK GRN) 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 junction block. When the headlamps are to be active, the DIM supplies ground via CKT 1485 (LT BLU) 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 via CKT 1970 (PNK/WHT). 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+) via CKT 712 (YEL) to the LH low beam headlamp. HDLOBMR Fuse supplies battery positive voltage (B+) via CKT 312 (TAN/WHT) or (YEL) to the RH low beam headlamp. The LH and RH low beam headlamps are both permanently grounded via CKT 1050 (BLK) to G401, so both low beam headlamps have power and ground, and then light.

The dash integration module (DIM) supplies battery positive voltage (B+) via CKT 1483 (DK GRN) 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 junction 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 via CKT 1969 (BLK/WHT). 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+) via CKT 711 (DK GRN/WHT) to the LH high beam headlamp. HDHIBMR Fuse supplies battery positive voltage (B+) via CKT 311 (LT GRN/WHT) or (DK GRN/WHT) to the RH high beam headlamp. The RH high beam headlamp is grounded via CKT 1050 (BLK) to G401. The LH high beam headlamp is grounded via CKT 250 (BLK) to G104. Both high beam headlamps have power and ground, and then light.

The flash-to-pass switch is permanently grounded via CKT 450 (BLK) to G201. When the headlamp dimmer switch is pulled toward driver, the flash-to-pass switch in the headlamp dimmer switch closes. The DIM Flash-To-Pass input is grounded via CKT 1484 (PNK/BLK). In response to this input, the DIM turns on the only high beam headlamps as described above. 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) via CKT 61 (YEL). The sensor is a light sensitive variable resistor that resistance varies as the outside ambient light level changes. The IPM receives an input voltage proportional to the resistance of the resistor via CKT 278 (WHT). 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.