Brake Booster Pressure Sensor Circuit Low

Your vehicle has a brake booster that helps make your braking easier. The sensor that tells the computer how much pressure is in the booster is not working properly, indicating less pressure than expected.

The brake booster pressure sensor should send a voltage signal between 0.5V (low pressure) and 4.5V (high pressure) to the Engine Control Module (ECM). If it reads below 0.5V, the code C0729 will trigger.

Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.

1. 11. Check brake fluid level; ensure it is within the recommended range. If low, top up and retest. Decision: Was the brake fluid level low? Yes - refill and retest. No - proceed to the next step.
2. 22. Inspect the wiring and connectors to the brake booster pressure sensor for corrosion or damage. Make sure all connections are secure. Decision: Are there any visible issues with wiring or connectors? Yes - repair as necessary and retest. No - proceed to step 3.
3. 33. Using a multimeter, measure voltage at the brake booster pressure sensor connector while someone operates the brake pedal. The voltage should rise based on pedal pressure. Decision: Is the voltage within the expected range of 0.5V to 4.5V? Yes - the sensor is likely good, and there may be an issue with the booster. No - proceed to step 4.
4. 44. Replace the brake booster pressure sensor if the voltage is outside the expected range, then retest. Decision: Did replacing the sensor clear the code? Yes - repair complete. No - further diagnosis of the brake booster may be needed.

• Faulty brake booster pressure sensor
• Wiring issues or bad connections
• Vacuum leaks in the brake booster system
• Corroded connectors
• Low brake fluid level

$$