Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Normal Operation and Fault Conditions
The ABS module uses a pressure sensor located inside the HCU to monitor the integrity of the hydraulic system. When the brake pedal is pressed, the ABS module compares the value of the brake fluid line pressure sensor to the BOO switch input from the PCM over the HS-CAN. If the brake fluid pressure sensor value is not comparable to the BOO switch input, the ABS module sets one or more DTCs.
| DTC | Description | Fault Trigger Conditions |
|---|---|---|
| C1A99:01 | Pressure Sensor: General Electrical Failure | This DTC indicates the brake fluid line hydraulic pressure sensor located inside the HCU has failed. |
| C1A99:28 | Pressure Sensor: Signal Bias Level Out of Range/Zero Adjustment Failure | This DTC indicates the brake fluid line hydraulic pressure sensor located inside the HCU has failed. |
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.