Pinpoint Test L: The Brake Warning Indicator Is Always On
Instrumentation, Message Center and Warning Chimes
Pinpoint Test L: The Brake Warning Indicator Is Always 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.
- DTC B2479 (Park Brake Switch Circuit Short to Ground)- an on-demand DTC that sets when the SJB (Smart Junction Box) detects a short to ground on the parking brake warning indicator switch input circuit during the module self-test.
- DTC C1125 (Brake Fluid Level Sensor Input Circuit Failure)- a continuous and on-demand DTC that sets in the SJB (Smart Junction Box) if the SJB (Smart Junction Box) detects a short to ground on the brake fluid level input circuit.
NOTE: If DTC U0140 is set in the IC (Instrument Cluster), other symptoms may also be present such as Tire Pressure Monitoring System (TPMS), instrument panel backlighting, and door ajar indication.
NOTE: Both the ABS warning indicator and the brake warning indicator illuminate if the input to turn on the brake warning indicator is received from the ABS module.
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- Parking brake warning indicator switch
- Brake fluid level switch
- ABS module
- SJB (Smart Junction Box)
- IC (Instrument Cluster)
PINPOINT TEST L : THE BRAKE WARNING INDICATOR IS ALWAYS ON
NOTICE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.
L1 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 off. Observe the brake warning indicator.
Does the brake warning indicator turn off when commanded off?
Yes
GO to L2.
No
INSTALL a new IC (Instrument Cluster). REFER to Instrument Cluster (IC) . TEST the system for normal operation.
L2 RETRIEVE THE RECORDED DTCs FROM THE IC (Instrument Cluster) SELF-TEST
- Check for recorded IC (Instrument Cluster) DTCs from the self-test.
Are any DTCs recorded?
Yes
For DTC U0140, GO to Pinpoint Test BC Pinpoint Test BC: DTC U0140.
For DTC U0121 (non-hybrid), GO to Pinpoint Test AZ Pinpoint Test AZ: DTC U0121.
For DTC U0129 (hybrid), GO to Pinpoint Test BA Pinpoint Test BA: DTC U0129.
For all other DTCs, REFER to DTC Charts Instrumentation, Message Center and Warning Chimes.
No
GO to L3.
L3 RETRIEVE THE RECORDED DTCs FROM THE ABS MODULE SELF-TEST
- Check for recorded ABS module DTCs from the self-test.
Are any DTCs recorded?
Yes
REFER to Antilock Brakes / Traction Control Systems.
No
GO to L4.
L4 RETRIEVE THE RECORDED DTCs FROM THE SJB (Smart Junction Box) SELF-TEST
- Check for recorded SJB (Smart Junction Box) DTCs from the self-test.
Is DTC B2479 recorded?
Yes
GO to L5.
No
GO to L8.
L5 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 and releasing the parking brake.
Does the PID agree with the parking brake position?
Yes
GO to L10.
No
GO to L6.
L6 CHECK THE PARKING BRAKE WARNING INDICATOR SWITCH
- Disconnect: Parking Brake Warning Indicator Switch C2015.
- Observe the brake warning indicator.
Does the brake warning indicator continue to illuminate?
Yes
GO to L7.
No
INSTALL a new parking brake warning indicator switch. CLEAR the DTCs. REPEAT the self-test.
L7 CHECK THE PARKING BRAKE WARNING INDICATOR SWITCH INPUT CIRCUIT FOR A SHORT TO GROUND
- Ignition OFF.
- Disconnect: SJB (Smart Junction Box) C2280C.
- Measure the resistance between the SJB (Smart Junction Box) C2280C-1, circuit CMC25 (WH/VT), harness side and ground.
Is the resistance greater than 10,000 ohms?
Yes
GO to L10.
No
REPAIR circuit CMC25 (WH/VT) for an open. CLEAR the DTCs. REPEAT the self-test.
L8 CHECK THE BRAKE FLUID LEVEL SWITCH OPERATION
- Ignition OFF.
- Disconnect: Brake Fluid Level Switch C124.
- Ignition ON.
Does the brake warning indicator turn off?
Yes
INSTALL a new brake fluid level switch. CLEAR the DTCs. REPEAT the self-test.
No
GO to L9.
L9 CHECK THE BRAKE FLUID LEVEL SWITCH INPUT CIRCUIT FOR A SHORT TO GROUND
- 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 ground.
Is the resistance less than 10,000 ohms?
Yes
GO to L10.
No
REPAIR circuit CMC19 (GY/VT) for a short to ground. REPEAT the self-test.
L10 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 verify that the concern is still present.
Is the concern still present?
Yes
INSTALL a new SJB (Smart Junction Box). 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.