Brake Warning Indicator Malfunction

/ 9-4x / 2011 / 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.

Diagnostic Fault Information

Circuit	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performance
Brake Fluid Level Signal	C0267 00	1	-	-
Brake Fluid Level Switch Ground	-	1	1	-
1. Brake Warning Indicator Malfunction

Circuit/System Description

Electronic brake control module (EBCM) monitors the brake fluid level in the brake fluid reservoir. When the fluid within the brake fluid reservoir is below the MIN level, contacts within the brake fluid level switch closes causing the voltage within the signal circuit to drop. The EBCM will detect the voltage drop and will send a serial data message to the instrument cluster commanding the brake warning indicator to illuminate.

Reference Information

Schematic Reference

Hydraulic Brake Schematics

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 the brake fluid level within the brake master cylinder reservoir, the fluid level should be above the MIN level.

2.	If not the specified condition, refer to Master Cylinder Reservoir Filling .

3.	Ignition ON, command the instrument cluster All Indicators ON and OFF with a scan tool, the brake warning indicator should turn ON and OFF while changing between the commanded states.

4.	If the brake warning indicator is always ON or always OFF, replace the instrument cluster.

Circuit/System Testing

1.	Ignition OFF, disconnect the harness connector at the B20 brake fluid level switch.

2.	Test for less than 1 Ω between the ground circuit terminal B 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 OK.

5.	If not the specified value, test the signal circuit terminal A for a short to ground. If the circuit tests normal, replace the K17 electronic brake control module (EBCM).

6.	Install a 3 A fused jumper wire between the signal circuit terminal A and the ground circuit terminal B, verify the scan tool Brake Fluid Level Sensor parameter is Low.

7.	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 (EBCM).

8.	If all circuits test normal, test or replace the B20 brake fluid level switch.

Component Testing

1.	Ignition OFF, disconnect the harness connector at the B20 brake fluid level switch.

2.	With the brake fluid in the brake master cylinder reservoir above the MIN level, test for infinite resistance between the signal terminal A and the ground terminal B.

3.	If not the specified value, replace the B20 brake fluid level switch.

4.	With the brake master cylinder reservoir empty, test for less than 2 Ω between the signal terminal A and the ground terminal B.

5.	If greater than the specified range, replace the B20 brake fluid level switch.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

•	Master Cylinder Reservoir Replacement

•	Control Module References for EBCM and instrument panel cluster replacement, setup and programming

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