Pinpoint Test I: The Brake Warning Indicator Is Never On
Instrumentation, Message Center and Warning Chimes
Pinpoint Tests
Pinpoint Test I: The Brake Warning Indicator Is Never On
Refer to Wiring Diagram Set 60, Instrument Cluster for schematic and connector information. Diagrams By Number
Refer to Wiring Diagram Set 42, Vehicle Dynamic Systems for schematic and connector information. Diagrams By Number
Normal Operation
The Instrument Cluster (IC) uses 3 basic messaged inputs to control the brake warning indicator. The first 2 are the parking brake warning indicator switch and the brake fluid level switch. The third is for the Electronic Brake Distribution (EBD), controlled by the ABS module. The parking brake warning indicator 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 EBD message is sent from the ABS module over the High Speed Controller Area Network (HS-CAN) communication bus lines. The parking brake warning indicator switch and the brake fluid level switch are hardwired to the SJB through separate signal and return circuits.
The SJB provides a reference voltage to both the parking brake warning indicator switch and the brake fluid level switch. When the parking brake is applied, the parking brake warning indicator switch closes to ground, providing a ground to the SJB and pulling the signal circuit low. When a low brake fluid level condition exists, the low brake fluid level switch closes to ground, pulling the signal circuit low. The SJB monitors the parking brake and the brake fluid level inputs sending the IC a message to turn the brake warning indicator on when the parking brake is applied, when the brake fluid level is low or if the SJB detects an open in the brake fluid level signal or return circuits. When the ABS module detects a base brake system concern or other ABS-related concerns that affect the EBD function, the ABS module sends a message to the IC to illuminate both the ABS warning indicator and the brake warning indicator.
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- Parking brake switch
- Brake fluid level switch (part of the master cylinder)
- ABS module
- SJB
- IC
PINPOINT TEST I: THE BRAKE WARNING INDICATOR IS NEVER ON
NOTICE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.
NOTE: Failure to disconnect the battery when instructed will result in false resistance readings. Refer to Battery.
-------------------------------------------------
I1 CARRY OUT THE IC INDICATOR LAMP ACTIVE COMMAND USING THE SCAN TOOL
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: IC DataLogger.
- Select the IC brake warning indicator (BRK_LAMP). Command the brake warning indicator on. Observe the brake warning indicator.
- Does the brake warning indicator illuminate when commanded on?
Yes
GO to I2.
No
INSTALL a new IC. REFER to Instrument Cluster (IC) Instrument Cluster (IC). TEST the system for normal operation.
-------------------------------------------------
I2 CHECK THE PARKING BRAKE SWITCH PID
- Enter the following diagnostic mode on the scan tool: SJB DataLogger.
- Select the SJB parking brake switch PID (PRK_BRK) while applying the parking brake.
- Does the PID agree with the parking brake position?
Yes
GO to I6.
No
GO to I3.
-------------------------------------------------
I3 CHECK THE PARKING BRAKE SWITCH
- Ignition OFF.
- Disconnect: Parking Brake Switch C2015.
- Ignition ON.
- Connect a fused jumper wire between the parking brake switch C2015-1, circuit GD143 (BK/VT), harness side and the parking brake switch C2015-2, circuit CCB09 (GY/BU), harness side.
- Does the brake warning indicator illuminate?
Yes
INSTALL a new parking brake switch. TEST the system for normal operation.
No
REMOVE the jumper wire. GO to I4.
-------------------------------------------------
I4 CHECK THE PARKING BRAKE SWITCH GROUND CIRCUIT FOR AN OPEN
- Disconnect: Negative Battery Cable.
- Measure the resistance between the parking brake switch C2015-1, circuit GD143 (BK/VT), harness side and ground.
- Is the resistance less than 5 ohms?
Yes
GO to I5.
No
REPAIR circuit GD143 (BK/VT) for an open. TEST the system for normal operation.
-------------------------------------------------
I5 CHECK THE PARKING BRAKE INPUT CIRCUIT FOR AN OPEN
- Disconnect: SJB C2280b.
- Measure the resistance between the SJB C2280b-18, circuit CCB09 (GY/BU), harness side and the parking brake switch C2015-2, circuit CCB09 (GY/BU), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to I9.
No
REPAIR circuit CCB09 (GY/BU) for an open. TEST the system for normal operation.
-------------------------------------------------
I6 CHECK THE ABS MODULE OPERATION
- Ignition OFF.
- Disconnect: Brake Fluid Level Switch C124.
- Ignition ON.
- Observe the brake warning indicator after the IC proves out.
- Does the brake warning indicator illuminate with the brake fluid level switch disconnected?
Yes
REMOVE the jumper wire. GO to I7.
No
REMOVE the jumper wire. GO to I8.
-------------------------------------------------
I7 CHECK THE BRAKE FLUID LEVEL SWITCH GROUND CIRCUIT FOR AN OPEN
- Disconnect: Negative Battery Cable.
- Measure the resistance between the brake fluid level switch C124-1, circuit GD120 (BK/GN), harness side and ground.
- Is the resistance less than 5 ohms?
Yes
INSTALL a new brake master cylinder. REFER to Hydraulic System, Brakes &/or Brake Pedal Assy. TEST the system for normal operation.
No
REPAIR circuit GD120 (BK/GN) for an open. TEST for normal operation.
-------------------------------------------------
I8 CHECK FOR CORRECT ABS MODULE OPERATION
- Disconnect the ABS module connector.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect the ABS module connector and make sure it seats correctly.
- Operate the system and verify that the concern is still present.
- Is the concern still present?
Yes
INSTALL a new ABS module. REFER to Antilock Brakes / Traction Control Systems. TEST the system for normal operation.
No
The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector.
-------------------------------------------------
I9 CHECK FOR CORRECT SJB OPERATION
- Disconnect all the SJB connectors.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect all the SJB connectors and make sure they seat correctly.
- Operate the system and verify that the concern is still present.
- Is the concern still present?
Yes
INSTALL a new SJB. REFER to Body Control Systems. TEST the system for normal operation.
No
The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector.
-------------------------------------------------