Test Description

WARNING: This page is about a different car, the 2002 GMC Safari and 2002 Chevrolet Astro. However, it is still accessible from the selected car via links, so may be relevant.

The numbers below refer to the step numbers on the diagnostic table.

2) - Listen for an audible click when the headlamp power or low beam relay operates. Command both the ON and OFF states. Repeat the commands as necessary.
3) - Verifies that the body control module is providing voltage to the headlamp power or low beam relay.
4) - Tests for an open in the ground circuit to the headlamp power or low beam relay.
5) - Tests if voltage is constantly being applied to the headlamp power or low beam relay.
6) - Tests for a short to ground on the control circuit of the headlamp power or low beam relay.
12) - After replacement of the BCM you must calibrate the new module for proper operation.

Fig 1: DTC B2577 Diagnosis (Steps 1-2)

Courtesy of GENERAL MOTORS CORP.

Fig 2: DTC B2577 Diagnosis (Steps 3-13)

Courtesy of GENERAL MOTORS CORP.