Brake Warning Indicator Malfunction

/ 9-5 (9650) / 2010 / 5. Brakes / Footbrake system / Fault diagnosis, fault symptoms / Brake Warning Indicator Malfunction

Diagnostic Instructions

•	Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

•	Review Strategy Based Diagnosis for an overview of the diagnostic approach.

•	Diagnostic Procedure Instructions provides an overview of each diagnostic category.

Circuit/System Description

The instrument cluster turns ON the brake warning indicator for 5 s after ignition ON. The body control module (BCM) monitors the parking brake switch and will request the instrument cluster via serial data to turn the brake warning indicator ON when the parking brake is applied. When the electronic brake control module (EBCM) detects a fault, it sends a serial data message to the instrument cluster commanding the indicator ON.

Reference Information

Schematic Reference

Hydraulic Brakes

Connector End View Reference

Component Connector End Views

Description and Operation

Hydraulic Brake System Description and Operation

Electrical Information Reference

•	Circuit Testing

•	Connector Repairs

•	Testing for Intermittent Conditions and Poor Connections

•	Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

1.	Inspect for proper brake fluid level. The fluid level should be above minimum level.

2.	If low, refer to Brake Fluid Loss .

3.	Ignition ON, with a scan tool command the instrument cluster All Indicators test ON and OFF. Verify the brake warning indicator turns ON and OFF.

4.	If the brake warning indicator does not turn ON and OFF, replace the P16 Instrument Cluster.

5.	Observe the scan tool BCM Park Brake Switch parameter while applying and releasing the parking brake. Verify the reading changes between Active and Inactive.

6.	If the parameter does not change between the specified values, proceed with Park Brake Switch Malfunction in Circuit/System Testing.

7.	Apply the parking brake. Verify the brake warning indicator turns ON.

8.	If the brake warning indicator does not turn ON, replace the K9 Body Control Module.

9.	Release the parking brake. Verify the brake warning indicator turns OFF.

10.	If the brake warning indicator does not turn OFF, proceed with Brake Fluid Level Switch Malfunction in Circuit/System Testing.

Circuit/System Testing

Note

Circuit/System Verification must be performed before Circuit/System Testing.

Brake Fluid Level Switch Malfunction

1.	Ignition OFF, disconnect the harness connector at the B20 Brake Fluid Level Switch.

2.	Test for less than 5 Ω between the ground circuit terminal 2 and ground.

3.	If greater than the specified range, test the ground circuit for an open/high resistance.

4.	Ignition ON, verify the scan tool Brake Fluid Level Sensor parameter is Low.

5.	If not the specified value, test the signal circuit for a short to ground. If the circuit tests normal replace the K17 Electronic Brake Control Module.

6.	Install a 3 A fused jumper wire between the signal circuit terminal 1 and ground.

7.	Verify the scan tool Brake Fluid Level Sensor parameter is OK.

8.	If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal replace the K17 Electronic Brake Control Module.

9.	If all circuits test normal, test or replace the B20 Brake Fluid Level Switch.

Component Testing

Brake Fluid Level Switch Test

1.	Ignition OFF, disconnect the harness connector at the B20 Brake Fluid Level Switch.

2.	Test for less than 5 Ω between the ground circuit terminal 2 and the signal circuit terminal 1.

3.	If less than the specified value, replace the B20 Brake Fluid Level Switch.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

•	Brake Fluid Level Indicator Switch Replacement

•	Control Module References for module replacement, setup and programming

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