Pinpoint Test M: The Brake Warning Indicator Is Always On
Instrumentation, Message Center and Warning Chimes
Pinpoint Tests
Pinpoint Test M: The Brake Warning Indicator Is Always On
Refer to Wiring Diagram Set 60, Instrument Cluster for schematic and connector information. Diagrams By Number
Refer to Wiring Diagram Set 13, Power Distribution/SJB for schematic and connector information. Diagrams By Number
Normal Operation
The brake warning indicator alerts the driver if any of the following brake system conditions are present: the parking brake is set, the brake fluid level is low, the ABS module detects a base brake system failure, there is a loss of communication between the Instrument Cluster (IC) and the Smart Junction Box (SJB), or there is a loss of communication between the IC and the ABS module.
When the parking brake is applied, circuit 1309 (RD/YE) to the SJB is grounded by the parking brake switch through circuit 1205 (BK). The SJB receives the ground signal and sends the IC a message over the communication network to illuminate the brake warning indicator. When the brake fluid level is low, the brake fluid level switch closes, providing a signal to the SJB on circuit 547 (LG/YE) which is then routed back to the SJB on the signal return circuit 512 (TN/LG). When a base brake system concern is detected, the ABS module sends a signal to the IC over the communication network to illuminate the brake system warning indicator.
- DTC B2479 (Brake Park Switch Circuit Short to Ground) - sets on-demand if the SJB detects that the parking brake is applied during the self-test or if there is a short to ground on the parking brake input circuit 1309 (RD/YE).
- DTC C1189 (Brake Fluid Level Sensor Input Short Circuit to Ground) - sets on-demand and continuously if the SJB detects that the brake fluid is low or there is a short to ground on the brake fluid level input circuit 547 (LG/YE).
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- Parking brake switch
- Brake fluid level switch
- SJB
- IC
PINPOINT TEST M: 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.
NOTE: Verify that the brake fluid level is full and the parking brake is fully released before proceeding with diagnostics.
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M1 RETRIEVE THE RECORDED DTCs FROM BOTH THE CONTINUOUS AND ON-DEMAND SJB SELF-TESTS
- Check for recorded SJB DTCs from the continuous and on-demand self-tests.
- Are any SJB DTCs recorded?
Yes
For DTC B2479, GO to M4.
For DTC C1189, GO to M6.
All other SJB DTCs, REFER to DTC Charts. Instrumentation, Message Center and Warning Chimes
No
GO to M2.
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M2 RETRIEVE THE RECORDED DTCs FROM BOTH THE CONTINUOUS AND ON-DEMAND ABS MODULE SELF-TESTS
- Check for recorded ABS module DTCs from the continuous and on-demand self-tests.
- Are any ABS module DTCs recorded?
Yes
REFER to Antilock Brakes / Traction Control Systems. Testing and Inspection
No
GO to M3.
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M3 CARRY OUT THE IC INDICATOR LAMP CONTROL 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) active command on while monitoring the brake warning indicator.
- Does the brake warning indicator illuminate?
Yes
GO to M9.
No
INSTALL a new IC. REFER to Instrument Cluster (IC) Instrument Cluster (IC). TEST the system for normal operation.
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M4 CHECK THE PARKING BRAKE SWITCH
- Ignition OFF.
- Disconnect: Parking Brake Switch C306.
- Ignition ON.
- Observe the brake warning indicator.
- Does the brake warning indicator continue to illuminate?
Yes
GO to M5.
No
INSTALL a new parking brake switch. CLEAR the DTCs. REPEAT the self-test.
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M5 CHECK CIRCUIT 1309 (RD/YE) FOR A SHORT TO GROUND
- Ignition OFF.
- Disconnect: SJB C2280c.
- Measure the resistance between the SJB C2280c-50, circuit 1309 (RD/YE), harness side and ground.
- Is the resistance greater than 10,000 ohms?
Yes
GO to M9.
No
REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test.
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M6 CHECK THE SJB OPERATION USING THE SCAN TOOL
- Ignition OFF.
- Disconnect: Brake Fluid Level Switch C124.
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: SJB DataLogger.
- Monitor the SJB brake fluid level (BRK_FLUID) PID.
- Does the PID indicate the brake fluid level is OK?
Yes
INSTALL a new brake fluid level switch. TEST the system for normal operation.
No
GO to M7.
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M7 CHECK CIRCUITS 512 (TN/LG) AND 547 (LG/YE) FOR A SHORT TO GROUND
- Ignition OFF.
- Disconnect: SJB C2280c.
- Measure the resistance between the SJB C2280c-35, circuit 512 (TN/LG), harness side and ground; and between the SJB C2280c-48, circuit 547 (LG/YE), harness side and ground.
- Are the resistances greater than 10,000 ohms?
Yes
GO to M8.
No
REPAIR the circuit in question. CLEAR the DTCs. REPEAT the self-test.
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M8 CHECK CIRCUITS 512 (TN/LG) AND 547 (LG/YE) FOR A SHORT TOGETHER
- Measure the resistance between the SJB C2280c-35, circuit 512 (TN/LG), harness side and the SJB C2280c-48, circuit 547 (LG/YE), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to M9.
No
REPAIR the circuit in question. CLEAR the DTCs. REPEAT the self-test.
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M9 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. 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. CLEAR the DTCs. REPEAT the self-test.
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