GM Service Manual Online
For 1990-2009 cars only

SYMPTOM

PROCEDURE

Important: Before proceeding with these diagnostics, check for DTCs. If DTCs are present, complete the associated diagnostics. If the condition still exists return to this chart.

Low beam headlamps inoperative, high beam OK.

Disconnect headlamp/turn switch connector. Probe pin A circuit 1201 with a test light-to-ground. Does the lamp light? If yes, faulty headlamp/turn switch. If no, open circuit 1201.

High beam headlamps inoperative, low beam OK.

Disconnect headlamp/turn switch connector. Probe pin G circuit 1200 with a test light-to-ground. Does the lamp light? If yes, faulty headlamp/turn switch. If no, open circuit 1200.

High and low beam headlamps inoperative.

Check circuit 550 at the headlamp switch for an open. If OK, faulty headlamp switch.

High beam indicator does not operate.

Perform the I/P cluster lamp and gage test using the scan tool. If high beam telltale does not illuminate, replace the bulb.

Right high beam headlamp, DRL, high beam TT inoperative.

Check the right high beam headlamp for open element. If OK, check for open 593 or 1200 circuit.

Left high beam headlamp, DRL, high beam TT inoperative.

Check the left high beam headlamp for an open element. If OK, check for an open circuit 40 or open circuit 1200.

DRL ON with headlamp switch ON, dimmer switch in low position.

Disconnect the BCM connector J2. Probe terminal J2-B08 circuit 1201 with a test light-to-ground. Does the lamp light? If no, open circuit 1201. If yes, faulty connection or BCM.

DRL inoperative, high beam TT lit with headlamp switch in any position.

Disconnect BCM connector J2. Probe terminal J2-A06 circuit 1200 with a test light to B+. Turn the headlamp switch ON, dimmer switch in the high beam position. Does the lamp light? If no, open circuit 1200. If yes, faulty connection or BCM.

DRL lamps do not turn OFF with park brake applied.

Disconnect BCM connector J2. Probe terminal J2-B02 circuit 1134 with a test light to B+. Apply the parking brake. Does the lamp light? If no, open circuit 1134. If yes, faulty connection or BCM.

DRL indicator does not operate.

Perform the I/P cluster lamp and gage test using the scan tool. If the telltale does not illuminate, replace the bulb.