Circuit Description

WARNING: This page is about a different car, the 1999 Pontiac Grand Am and 1999 Oldsmobile Alero. However, it is still accessible from the selected car via links, so may be relevant.

This DTC indicates that the Automatic Lighting Control (ALC) relay output is shorted to ground. DTC B2577 will set if all of the following conditions occur:

Ambient light sensor indicates bright conditions.
Ignition switch is not cranking engine.
Ignition 1 is active.
Ignition 3 is active.
Engine is not running (class 2 message).
ALC relay output is not active.
ALC headlight feedback is present for 5 seconds.

When DTC sets, SERVICE VEHICLE SOON indicator will come on and check gauges chime will sound. DTC will clear if BCM reads proper headlight voltage or senses that conditions for DTC are no longer present. DTC will clear from history after ignition switch is cycled on and off 100 times with no faults present. DTC can also be cleared using scan tool.