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 Descriptors

DTC C0126 00: Brake Fluid Switch Fault

### Circuit/System Description

The instrument panel cluster (IPC) illuminates the BRAKE indicator and sends a serial data message in order to activate an audible warning when the following occurs, the IPC detects a low brake fluid condition--signal circuit is low or performs the displays test at the start of each ignition cycle. The indicator illuminates for approximately 5 seconds. The IPC illuminates the CHECK BRAKE FLUID indicator in the driver information center (DIC) and sends a serial data message in order to activate an audible warning when the IPC detects that the brake fluid level is below the normal operating range.

### Conditions for Running the DTC

• | Ignition switch is in the ON position.

• | System voltage is 4 volts.

### Conditions for Setting the DTC

The DTC will set when the IPC detects greater then 4.0 volts from the brake fluid switch.

### Conditions for Clearing the DTC

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

• | The DTC can be cleared using a scan tool.

### Diagnostic Aids

The brake fluid level switch is an integral part of the master cylinder reservoir and cannot be replaced as an independent component.

### Reference Information

#### Schematic Reference

Instrument Cluster Schematics

#### Connector End View Reference

Component Connector End Views

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool Reference

Control Module References

### Circuit/System Testing

1. Ensure that there is sufficient fluid in the brake reservoir.
2. Ignition OFF, disconnect the harness connector at the brake fluid level switch.
3. Ignition ON, test for voltage between the brake fluid level switch signal circuit and a known ground.

⇒ | If the voltage is greater than 4.0 volts, test the brake fluid level switch signal circuit for a short to voltage, if the circuit tests normal replace the IPC.

⇒ | If the voltage is less than 4.0 volts, test the brake fluid level switch signal circuit for a short to ground or an open/high resistance, if the circuit tests normal replace the IPC.

4. Ignition OFF, test for less than 1 ohm of resistance between the brake fluid level switch ground circuit and a known ground.

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

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

### Component Testing

1. Ignition OFF, disconnect the harness connector at the brake fluid level switch.
2. Ensure that there is sufficient fluid in the brake reservoir.
3. Test for infinite resistance between the brake fluid level switch signal and ground terminals.

⇒ | If not the specified value, replace the brake fluid level switch.

Caution: Brake fluid may irritate eyes and skin. In case of contact, take the following actions:

• | Eye contact--rinse thoroughly with water.

• | Skin contact--wash with soap and water.

• | If ingested--consult a physician immediately.

Notice: Avoid spilling brake fluid on any of the vehicle's painted surfaces, wiring, cables or electrical connectors. Brake fluid will damage paint and electrical connections. If any fluid is spilled on the vehicle, immediately flush the area with water to minimize the potential for damage.

4. Siphon the brake fluid out of the master cylinder reservoir using a hand vacuum pump.
5. Test for less than 1 ohm between the brake fluid level switch signal and ground terminals.

⇒ | If greater than the specified value, replace the brake fluid level switch.

### Repair Instructions

Important: Always perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Master Cylinder Reservoir Replacement

• | Control Module References for IPC replacement, setup, and programming