Diagnosis

TROUBLESHOOTING HINTS:
1. CHECK the condition of LT HDLP Fuse 19, RT HDLP Fuse 20, FOG LP Fuse 28 and HDLP SWITCH Fuse 1. If any fuse is open, LOCATE and REPAIR cause of overload and REPLACE fuse.
2. CHECK that G102 is clean and tight.
3. CHECK for an open or shorted filament within the inoperative headlamp.
4. CHECK that DRL Relay, Headlamp Power Relay, and Headlamp Ground Relay are all securely connected.
5. CHECK for a broken (or partially broken) wire inside the insulation which could cause system malfunction but prove GOOD in a continuity/voltage check with a system disconnected. These circuits may be intermittent or resistive when loaded, and if possible, should be checked by monitoring for a voltage drop with the system operational (under load) CHECK for proper installation of aftermarket electronic equipment which may affect the integrity of other systems.

DIAGNOSTIC AIDS

IMPORTANT:
- Use the appropriate probe from the J 35616-A connector test adapter kit for ANY probing of the Bussed Electrical Centers (BECs) in this table to avoid damage to the BECs.
- Perform a visual check of the wiring and connectors.
- Refer to Wiring Systems for intermittent and poor connections.

CIRCUIT OPERATION

HEADLAMPS - LOW BEAM
Voltage to the Headlamps Switch is available at all times through the HDLP SWITCH Fuse and the CKT 1940 (ORN) wire. When the Headlamp Switch is turned to the HDLP position, the Headlamp Power Relay coil is energized through the CKT 352 (WHT) wire. A signal is also sent to the Body Control Module (BCM) that the Headlamps are switched ON.

When the Headlamp Switch is in the AUTO position, a light sensor located in the RH speaker grill senses a daylight or dark condition. The Body Control Module (BCM) will control the actuation of the Headlamp Power Relay, Headlamp Ground Relay, and the DRL Relay for DRL operation during a daylight condition. When the light sensor detects a dark condition, the Body Control Module will produce a signal that will energize only the Headlight Power Relay, through the CKT 352 (WHT) wire.

The Headlamp Power Relay coil is grounded through the Underhood Bussed Electrical Center (UBEC), through pin F7 of connector 2, and through the CKT 350 (BLK) circuit to G102.

The Headlamp Power Relay supplies current to both the LT HDLP and the RT HDLP fuses. The Headlamp Low Beam Bulb, LH receives current through the CKT 712 (YEL) wire. The Headlamp Low Beam Bulb, RH receives current through the CKT 198 (DK BLU) wire. Both Headlamp Low Beam Bulbs are grounded through a CKT 525 (YEL) circuit, through the UBEC, through the Multifunction Switch (Low position), back to the UBEC through the CKT 10 (YEL) circuit to the Headlamps Ground Relay. The Headlamps Ground Relay, and the DRL Relay are deenergized by the Body Control Module (BCM), providing a ground path through the normally open contacts of the Headlamps Ground Relay. The ground path is completed through the UBEC and to G102 through the CKT 350 (BLK) circuit.

HEADLAMPS / CONVENTIONAL - HIGH BEAM
Voltage to the Headlamps Switch is available at all times through the HDLP SWITCH Fuse and the CKT 1940 (ORN) wire. When the Headlamp Switch is turned to HDLP, the Headlamp Power Relay coil is energized through the CKT 352 (WHT) wire. A signal is also sent to the Body Control Module that the Headlamps are switched on. The Headlamp Power Relay coil is grounded through the Underhood Bussed Electrical Center (UBEC), through pin F7 of connector 2, and through the CKT 350 (BLK) circuit to 0102.

The Headlamp Power Relay supplies current to both the LT HDLP and the RT HDLP fuses. The Headlamp High Beam Bulb, RH receives current through the CKT 198 (DK BLU) wire from the RT HDLP Fuse. When the Headlamps Switch is in the HDLP position, the Body Control Module (BCM) removes the ground path to the relay coil of the Headlamps Ground Relay and the DRL Relay. Both relays return to the normally open condition. The normally open contacts of the DRL Relay allows current to the Headlamp High Beam Bulb, LH, through the CKT 711 (DK GRN/ WHT) circuit.

Both Headlamp High Beam Bulbs are grounded through the CKT 524 (PPL) circuit through the UBEC, through the Multifunction Switch (High position), back through the UBEC, to the Headlamps Ground Relay. Because the relay is deenergized, the current flows through the normally open contacts of the relay, through the UBEC, and through the CKT 350 (BLK) circuit to G102. A voltage signal is sent to the Body Control Module (BCM), through the CKT 524 (PPL) wire, to confirm proper high beam operation.

HEADLAMPS / CONVENTIONAL - DAYTIME RUNNING LAMPS
Voltage to the Headlamps Switch is available at all times through the HDLP SWITCH Fuse and the CKT 1940 (ORN) wire. When the Headlamp Switch is in the AUTO position, a light sensor located in the RH speaker grill senses a daylight or dark condition. The Body Control Module (BCM) will control the operation of the Headlamp Power Relay, Headlamp Ground Relay, and the DRL Relay for DRL operation during a daylight condition.

The Headlamp Power Relay coil is grounded through the Underhood Bussed Electrical Center (UBEC), through pin F7 of connector 2, and through the CKT 350 (BLK) circuit to G102.

The Headlamp High Beam Bulb, RH receives current through the CKT 198 (DK BLU) wire. The BCM energizes the Headlamp Ground Relay and the DRL Relay. When the Headlamp Ground Relay is energized, the ground path for regular headlamp operation is eliminated. At the same time, the DRL Relay is energized, which now places both Headlamp High Beam Bulbs in series. This operation will cause both headlights to light at half normal output. The ground circuit for the Daytime Running Lights is through the CKT 711 (DK GRN/WHT) wire through the DRL Relay (closed contacts), through the UBEC, to the CKT 350 (BLK) circuit to G102.

A voltage signal is sent to the Body Control Module (BCM), through the CKT 524 (PPL) wire, to confirm proper DRL operation.