B2600

Diagnostic Chart 1:

Diagnostic Chart 2:

Refer to Headlights/Daytime Running Lights (DRL) Schematics.

CIRCUIT DESCRIPTION
The daytime running lamps (DRL) are controlled by the body control module (BCM). The BCM grounds circuit 592 in order to energize the DRL relay coil. This action places both low and high beam headlamps (Oldsmobile - high beams only) in series with each other with the DRL relay terminal 87 providing ground and the RH HDLP fuse providing battery positive voltage. The BCM monitors the low (1201) and high (1200) beam circuits to ensure that the DRLs are operating properly. If the BCM senses that the DRLs are not operating properly DTC B2600 is set.

CONDITIONS FOR RUNNING THE DTCs
^ The ignition switch is on.
^ The headlamp switch is off.
^ The park brake is unapplied.
^ The transaxle is in gear.

CONDITIONS FOR SETTING THE DTC
One or more of the following conditions is/are present:
^ Circuit 592 is open.
^ Circuit 593 is open.
^ Circuit 41 is open.
^ Circuit 640 is open.
^ Circuit 1200 is open.
^ Circuit 1201 is open (Pontiac only).
^ Circuit 150 is open.

ACTION TAKEN WHEN THE DTC SETS
^ The BCM turns off the DRL relay for the remainder of the ignition cycle.
^ The SERVICE VEHICLE SOON indicator lights.
^ The check gauges chime sounds.

CONDITIONS FOR CLEARING THE DTC
^ A current DTC B2600 clears when the malfunction is no longer present and the ignition switch Is cycled.
^ All BCM history codes clear after 100 ignition cycles (from OFF to ON) with no current codes active during the 100 ignition cycles.

DIAGNOSTIC AIDS
^ Diagnose all other DRL DTCs before DTC B2600.
^ An open headlamp bulb may set this DTC.
^ If the DTC is a history DTC. the problem may be intermittent. Perform the tests while wiggling the wiring and connectors. This may often cause the malfunction to appear.

TEST DESCRIPTION
The number(s) below refer to the step number(s) on the diagnostic table.
4. Listen for an audible click when the DRL relay operates. Command both the ON and OFF states. Repeat the commands as necessary.
5. Tests for voltage at the coil side of the DRL relay.
6. Verifies that the body control module is providing ground to the DRL relay.