K 1500 Truck 4WD V6-4.3L VIN W (1997)
Brake Warning Indicator: Initial Inspection and Diagnostic Overview
Circuit Operation
Battery voltage is applied through the GAUGES FUSE 4 to the "BRAKE" Indicator when the Ignition Switch is in the RUN, BULB TEST or START
positions. The "BRAKE" Indicator can be lit by having ground applied to it from any of three switches or the Electronic Brake Control Module (EBCM
).
The "BRAKE" Indicator will light whenever the Parking Brake is engaged. When the Parking Brake is engaged, ground is supplied through the closed
contacts of the Parking Brake Warning Switch to the "BRAKE" indicator. The "BRAKE" Indicator lights to alert the driver that the Parking Brake is
engaged.
The "BRAKE" Indicator will light when the Ignition Switch is turned from the "LOCK" to the RUN position. This is when the Electronic Brake Control
Module (EBCM) conducts its initial test which entails lighting the BRAKE" Indicator and the ABS Indicator. The Electronic Brake Control Module
(EBCM) will also light the "BRAKE" Indicator if there is a malfunction within the Antilock Brake System which is affecting the operation of the base
Hydraulic Braking system.
The "BRAKE" Indicator will light if there is low Brake fluid pressure in the front or rear Brakes. When the Combination Valve senses low Brake fluid
pressure in the front or rear brakes it closes the Brake Pressure Warning Switch. A ground is supplied through the closed contacts of the Brake Pressure
Warning Switch to the "BRAKE" Indicator. With both power and ground applied to the "BRAKE" Indicator, it will light.
The "BRAKE" Indicator will also light whenever the Ignition Switch is turned to the BULB TEST position.
The Daytime Running Lamps Module senses ground through the Park Brake Warning Switch. When this input is grounded, the Daytime Running Lamps
are not energized.
The "BRAKE" Indicator will also light whenever the Ignition Switch is turned to the BULB TEST Position.
Troubleshooting Hints
1. CHECK condition of GAUGES FUSE 4. If Fuse is Open, LOCATE and REPAIR source of overload and REPLACE Fuse.
2. CHECK that Engine Ground G105, and I/P Ground G200 is clean and tight.
3. CHECK the "BRAKE" Indicator Bulb for an open filament.
4. CHECK that the Parking Brake is fully released.
5. Make sure that there is an adequate amount of Brake fluid in the reservoir.
6. If any ABS Diagnostic Codes are Set, Refer to Brakes and Traction Control. See:
7. If the Brake Indicator only lights for the Ignition Switch in BULB test or for the Park Brake Warning Switch, then Diode 1 in the Underhood
Fuse-Relay Center may have opened.
^
CHECK for a broken (or partially broken) wire inside of the insulation which could cause system malfunction but prove "GOOD" in a
Continuity/Voltage check with a system disconnected. These Circuits may be intermittent or resistive when loaded, and if possible, should be
checked by monitoring for a Voltage drop with the system operational (under load).
^
CHECK for proper installation of aftermarket electronic equipment which may affect the integrity of other systems (Refer "Troubleshooting
Procedures"). See: Diagrams/Diagnostic Aids
