For 1990-2009 cars

### 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.

### DTC Descriptor

DTC C0126 00: Low Brake Fluid Indicated

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Brake Fluid Level Signal | 1 | C0126 00 | C0126 00 | --
Park Brake Signal | 1 | 1 | 1 | --
Ground | -- | C0126 00 | -- | --
1. Brake Warning Indicator Malfunction

### Circuit/System Description

The brake fluid level switch monitors the level of brake fluid in the master cylinder. When the instrument panel cluster (IPC) sees the brake fluid level switch input closed, it turns ON the Red Brake Warning indicator and sends a serial data message to the electronic brake control module (EBCM) that the brake fluid level is low.

### Conditions for Running the DTC

Ignition ON.

### Conditions for Setting the DTC

• | A short to voltage or open/high resistance on the signal circuit.

• | An open/high resistance on the ground circuit.

### Action Taken When the DTC Sets

• | The EBCM disables the antilock brake system (ABS)/traction control system (TCS) and vehicle stability enhancement system (VSES).

• | A DIC message and/or a warning indicator may be displayed.

### Conditions for Clearing the DTC

• | The condition for the DTC is no longer present.

• | The EBCM clears the history DTC when a current DTC is not detected in 100 consecutive drive cycles.

### Reference Information

#### Schematic Reference

Hydraulic Brake Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

Brake Warning 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

Inspect for proper brake fluid level, the fluid level should be at or above the proper level.

⇒ | If low, refer to Brake Fluid Loss

### Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the brake fluid level switch.
2. Test for less than 5 ohms between the ground circuit terminal 2 and ground.

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

3. Ignition ON, test for 4.8 - 5.2 volts between the 5 volt reference circuit terminal 1 and ground.

⇒ | If less than the specified range, test the 5 volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the IPC.

⇒ | If greater than the specified range, test the 5 volt reference circuit for a short to voltage. If the circuit tests normal, replace the IPC.

4. If all circuits test normal, test or replace the 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 IPC replacement, setup, and programming