On some earlier production vehicles, the DRL will turn OFF when the turn signal lamps are activated. This is controlled by the BCM and is a normal condition. The daytime running lights operate when the following conditions are present:
| • | The ignition switch is in the ON position. |
| • | The headlamp switch is in the AUTO or PARK position. |
| • | The park brake is released. |
| • | The automatic transmission is shifted out of the PARK position (if equipped). |
| • | The ambient light sensor senses a daylight condition. |
When all conditions are present the body control module (BCM) will turn the daytime running lights ON.
During normal operation, current flows to the RT HDLP fuse from the closed contacts of the energized headlamp power relay. From the RT HDLP fuse, current flows through CKT 198 (DK BLU) to the RH high beam headlamp to the LH high beam headlamp through CKT 524 (PPL). The normal ground is removed by the energized headlamp grounding relay. CKT 524 also provides a voltage signal to the BCM in order to confirm proper DRL operation. The LH high beam headlamp receives a new ground through CKT 711 (DK GRN/WHT) to the normally open contacts of the daytime running lamp relay through CKT 350 (BLK) to G102.
When the headlamp switch is in the AUTO or PARK position, the ambient light sensor (located in the right speaker grill) senses either daylight or darkness and sends the signal to the BCM. When the ambient light sensor detects a daylight condition, the BCM will activate the following three relays:
| • | The headlamp power relay |
| • | The headlamp grounding relay |
| • | The daytime running lamp (DRL) relay |
The headlamp power relay provides power to the high beam headlamps.
The headlamp grounding relay removes the ground path for regular headlamp operation.
The daytime running lamp (DRL) relay provides a new ground that places both high beam headlamps in a series. This operation causes the high beam headlamps to operate at half normal output.
The BCM will activate the headlamp power relay by providing power to the relay coil through CKT 352 (WHT) The relay coil is grounded through terminal F7 connector 2 of the underhood fuse block to CKT 350 (BLK) to G102. The BCM will activate the headlamp grounding relay by providing a ground to the coil through CKT 592 (LT GRN/BLK). Power is provided to the coil through CKT 240 (ORN) from the PARK LP fuse. The BCM will activate the daylight running lamp relay by providing a ground to the coil through CKT 592 (LT GRN/BLK). Power is provided to the coil by the FOG LP fuse. A voltage signal is sent to the BCM through CKT 524 (PPL) in order to confirm high beam operation.
ZR2
On a vehicle with the ZR2 option, the daytime running lights utilize the low beam headlamps equipped with a long life bulb in a parallel circuit. Voltage is supplied by the headlamp power relay to each low beam headlamp bulb and ground is controlled by the DRL relay. When the BCM requests the DRL ON, it will apply voltage to the headlamp power relay coil and ground to the DRL relay coil closing the contacts. This completes the power and ground circuits to the low beam headlamp bulbs. The parameters required to operate the system are the same as a vehicle without the ZR2 option.
