S15/T15 Sonoma P/U 2WD V6-4.3L VIN W (1996)
Brake Warning Indicator: Initial Inspection and Diagnostic Overview
Circuit Operation
Battery voltage is supplied to the Brake Indicator through the GAUGES Fuse and the PNK (39) wire when the Ignition Switch is in RUN or START.
Ground is provided through the TAN/WHT (33) and LT BLU (1134) wire by the Park Brake Warning Switch, Brake Pressure Warning Switch or the
TAN/WHT (33) and PPL (680) and the Brake Pressure Modulator Valve (BPMV).
The Park Brake Warning Switch closes when the Parking Brake is applied. The Brake Indicator lights to alert the driver.
The Brake Pressure Warning Switch closes to light the BRAKE Indicator when there is low brake fluid pressure in one of the two hydraulic brake
systems. This could be caused by a leak in one of the brake lines. Refer to Switch reset procedure. This can only be accomplished after the system has
been repaired.
The 2.2 L Engine's Electronic Brake Control Module (Part of the Brake Pressure Modulator Valve) or the 4.3 L Engines Vehicle Control Module
grounds the BRAKE Indicator when the module senses certain malfunctions in the hydraulic portion of the system. The module grounds the ANTILOCK
Indicator when the module senses a malfunction in the electrical or electronic portion of the system. Brake voltage input is supplied to the module
through the TCC Brake and Cruise Control Release Switch whenever the brakes are applied. For the Four-Wheel Antilock Brake System Description and
Diagnosis refer to Antilock Brake System. See: Brakes and Traction Control/Antilock Brakes / Traction Control Systems
Troubleshooting Hints
1. Check the condition of the BRAKE warning lamp.
2. Check GAUGES fuse. If fuse is open, check for short to ground in PNK (39) wire between I/P Fuse Block and Instrument Cluster connector.
3. Check that grounds G102, G104, G107 and G180 are clean and tight.
4. Check brake fluid level.
5. If brake fluid reservoir is empty or very low, and BRAKE warning lamp does not light, check Brake Pressure Warning Switch.
6. If equipped with Anti-lock Brakes and BRAKE warning lamp is lit, check for trouble codes.
7. If equipped with VCM and BRAKE warning lamp is lit, check for trouble codes. Refer to Engine Controls.
