Test L: The Brake Warning Indicator Is Never On
PINPOINT TEST L: THE BRAKE WARNING INDICATOR IS NEVER ONL1-L2:
L3-L5:
L5-L8:
L8-L10:
Normal Operation
The instrument cluster uses 3 basic messaged inputs to control the brake warning indicator. The first 2 are the parking brake switch and brake fluid level switch. The third is for the electronic brake distribution, controlled by the anti-lock brake system (ABS). The parking brake switch and the brake fluid level switch status are sent from the smart junction box (SJB) over the medium speed controller area network (MS-CAN) communication bus. The electronic brake distribution message is sent from the ABS module over the HS-CAN communication bus lines. The parking brake switch is hardwired to the SJB through circuit CCB01 (VT/BN). The brake fluid level switch is hardwired to the SJB through signal circuit CMC19 (GY/VT) and return circuit RMC19 (YE/GY). When the parking brake is applied, the parking brake switch closes to ground through circuit GD143 (BK/VT), providing a ground to the SJB and pulling circuit CCB01 (VT/BN) low. When a low brake fluid level condition exists, the low brake fluid level switch closes to ground through circuit GD120 (BK/GN), pulling circuit CMC19 (GY/VT) low. The SJB monitors the parking brake and low brake fluid level inputs and sends the instrument cluster a message to turn on the brake warning indicator when the parking brake is applied or the brake fluid is low. When the ABS module detects a base brake system concern or other ABS related concerns that affect the electronic brake distribution function, the ABS module sends a message to the instrument cluster to illuminate both the ABS warning indicator and the brake warning indicator.
Possible Causes
- Circuit CCB01 (VT/OG) open
- Circuit GD120 (BK/GN) open
- Circuit GD143 (BK/VT) open
- Master cylinder (brake fluid level switch)
- Brake fluid level switch
- SJB
- Instrument cluster