GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The brake fluid level switch monitors the level of brake fluid in the master cylinder. When the IPC sees the brake fluid level switch input grounded, it turns ON the red Brake indicator and sends a serial data message to the EBCM that tells the EBCM that the brake fluid level is low.

Conditions for Running the DTC

The ignition is ON.

Conditions for Setting the DTC

The EBCM receives a serial data message from the IPC indicating that the brake fluid level is low.

Action Taken When the DTC Sets

    • The EBCM disables the TCS until the DTC becomes a history DTC.
    • The red Brake warning indicator turns ON.
    • The Traction Off indicator turns ON.
    • The message center displays the Service Traction System message.
    • The ABS remains functional.

Conditions for Clearing the DTC

    • The condition for the DTC is no longer present and the DTC is cleared with a scan tool.
    • The electronic brake control module (EBCM) automatically clears the history DTC when a current DTC is not detected in 100 consecutive drive cycles.

Diagnostic Aids

Inspect the master cylinder reservoir for the proper brake fluid level.

Step

Action

Yes

No

Schematic Reference: Brake Warning System Schematics

Connector End View Reference: Hydraulic Brake Connector End Views

1

Did you perform the Hydraulic Brake Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - Hydraulic Brakes

2

Inspect the brake fluid level.

Is the brake fluid level OK?

Go to Step 3

Go to Brake Fluid Loss

3

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, observe the Low Brake Fluid parameter in the Instrument Panel Cluster data list.

Does the scan tool indicate that the Low Brake Fluid parameter is Off?

Go to Testing for Intermittent Conditions and Poor Connections

Go to Step 4

4

  1. Turn OFF the ignition.
  2. Disconnect the brake fluid level switch.
  3. Turn ON the ignition, with the engine OFF.
  4. With a scan tool, observe the Low Brake Fluid parameter.

Does the scan tool indicate that the Low Brake Fluid parameter is Off?

Go to Step 6

Go to Step 5

5

Test the signal circuit of the brake fluid level switch for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 8

Go to Step 7

6

Replace the brake fluid level switch. Refer to Brake Fluid Level Indicator Switch Replacement .

Did you complete the repair?

Go to Step 8

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7

Important: Perform the setup procedure for the replacement IPC.

Replace the instrument cluster (IPC). Refer to Instrument Cluster Replacement .

Did you complete the repair?

Go to Step 8

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8

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2