Pinpoint Test K: The Brake Warning Indicator Is Never On
Instrumentation, Message Center and Warning Chimes
Pinpoint Test K: The Brake Warning Indicator Is Never On
Refer to Wiring Diagram Set 60, Instrument Cluster for schematic and connector information Electrical Diagrams.
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 (Electronic Brake Distribution) 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 (Smart Junction Box) through separate signal and return circuits.
The SJB (Smart Junction Box) 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 (Smart Junction Box) 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 (Smart Junction Box) monitors the parking brake and the brake fluid level inputs sending the IC (Instrument Cluster) 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 (Smart Junction Box) 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 (Electronic Brake Distribution) function, the ABS module sends a message to the IC (Instrument Cluster) 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
- Brake fluid level switch
- Parking brake warning indicator switch
- SJB (Smart Junction Box)
- IC (Instrument Cluster)
PINPOINT TEST K : 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.
K1 CARRY OUT THE IC (Instrument Cluster) INDICATOR LAMP CONTROL ACTIVE COMMAND USING THE SCAN TOOL
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: IC (Instrument Cluster) DataLogger.
- Select the IC (Instrument Cluster) brake warning indicator (BRK_LAMP) active command. Command the brake warning indicator on and observe the brake warning indicator.
Does the brake warning indicator illuminate when commanded on?
Yes
GO to K2.
No
INSTALL a new IC (Instrument Cluster). REFER to Instrument Cluster (IC) . TEST the system for normal operation.
K2 DETERMINE IF THE BRAKE WARNING INDICATOR OPERATES WITH THE PARKING BRAKE
- Apply the parking brake while monitoring the brake warning indicator.
Does the brake warning indicator illuminate with the parking brake applied?
Yes
GO to K7.
No
GO to K3.
K3 CHECK THE PARKING BRAKE SWITCH PID
- Enter the following diagnostic mode on the scan tool: SJB (Smart Junction Box) DataLogger.
- Select the SJB (Smart Junction Box) parking brake (PRK_BRAKE) PID. Monitor the parking brake PID while applying the parking brake.
Does the PID agree with the parking brake position?
Yes
GO to K9.
No
GO to K4.
K4 CHECK THE PARKING BRAKE WARNING INDICATOR SWITCH
- Ignition OFF.
- Disconnect: Parking Brake Warning Indicator Switch C2015.
- Connect a fused jumper wire between the parking brake warning indicator switch C2015-1, circuit GD182 (BK/GY), harness side and the parking brake warning indicator switch C2015-2, circuit CMC25 (WH/VT), harness side.
- Ignition ON.
- Monitor the brake warning indicator.
Does the brake warning indicator illuminate?
Yes
REMOVE the jumper wire. INSTALL a new parking brake warning indicator switch. TEST the system for normal operation.
No
REMOVE the jumper wire. GO to K5.
K5 CHECK THE PARKING BRAKE WARNING INDICATOR SWITCH GROUND CIRCUIT FOR AN OPEN
- Ignition OFF.
- Disconnect: Negative Battery Cable.
- Measure the resistance between the parking brake switch C2015-1, circuit GD182 (BK/GY), harness side and ground.
Is the resistance less than 5 ohms?
Yes
GO to K6.
No
REPAIR circuit GD182 (BK/GY) for an open. TEST the system for normal operation.
K6 CHECK THE PARKING BRAKE WARNING INDICATOR SWITCH SIGNAL CIRCUIT FOR AN OPEN
- Disconnect: SJB (Smart Junction Box) C2280C.
- Measure the resistance between the SJB (Smart Junction Box) C2280C-1, circuit CMC25 (WH/VT), harness side and the parking brake switch C2015-2, circuit CMC25 (WH/VT), harness side and ground.
Is the resistance less than 5 ohms?
Yes
GO to K10.
No
REPAIR circuit CMC25 (WH/VT) for an open. TEST the system for normal operation.
K7 CHECK THE BRAKE FLUID LEVEL SWITCH
NOTE: Verify that the brake fluid level is low or was low prior to either adding brake fluid or a brake system repair.
- Ignition OFF.
- Disconnect: Brake Fluid Level Switch C124.
- Connect a fused jumper wire between the brake fluid level switch C124-1, circuit GD120 (BK/GN), harness side and the brake fluid level switch C124-2, circuit CMC19 (GY/VT), harness side.
- Ignition ON.
- Monitor the brake warning indicator.
Does the brake warning indicator turn on?
Yes
INSTALL a new brake fluid level switch. TEST the system for normal operation.
No
REMOVE the jumper wire. GO to K8.
K8 CHECK THE BRAKE FLUID LEVEL INPUT CIRCUIT FOR AN OPEN
- Ignition OFF.
- Disconnect: SJB (Smart Junction Box) C2280F.
- Measure the resistance between the SJB (Smart Junction Box) C2280F-9, circuit CMC19 (GY/VT), harness side and the brake fluid level switch C124-2, circuit CMC19 (GY/VT), harness side; and between the SJB (Smart Junction Box) C2280F-22, circuit CMC19 (GY/VT), harness side and the brake fluid level switch C124-2, circuit CMC19 (GY/VT), harness side.
Is the resistance less than 5 ohms?
Yes
GO to K9.
No
REPAIR circuit CMC19 (GY/VT) for an open. TEST the system for normal operation.
K9 CHECK THE BRAKE FLUID LEVEL 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
GO to K10.
No
REPAIR circuit GD120 (BK/GN) for an open. TEST the system for normal operation.
K10 CHECK FOR CORRECT SJB (Smart Junction Box) OPERATION
- Disconnect all the SJB (Smart Junction Box) connectors.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect all the SJB (Smart Junction Box) connectors and make sure they seat correctly.
- Operate the system and determine if the concern is still present.
Is the concern still present?
Yes
INSTALL a new SJB (Smart Junction Box). CLEAR the DTCs. REPEAT the self-test.
No
The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. CLEAR the DTCs. REPEAT the self-test.