The brake booster pressure sensor (5 V reference, signal, ground) measures the vacuum in the brake booster. On direct-injection, turbo, stop-start and hybrid engines intake vacuum is scarce, so the engine module watches it and creates vacuum when needed – closing the throttle, suppressing engine stop or running an electric vacuum pump. That makes it an input to idle and throttle control. P0555 is the general circuit fault without low/high distinction. No manufacturer document available to us uses it; GM splits circuit faults into P0557 and P0558. The module then assumes a substitute value and keeps vacuum available as a precaution.
Medium severity. Can I keep driving?Drive without demanding power and go to a repair shop soon. If you see a lot of blue smoke or hear a metallic noise, shut off the engine.
Symptoms
- Check engine light or brake booster warning
- Stop-start inactive
- Often no change in driving
Most likely causes
- Connector or wire to the sensor open or corroded
- Sensor faulty
- 5 V reference disturbed (short at another sensor on the same reference)
- Engine module
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: medium
What each character of P0555 means
- P: Powertrain: engine and transmission
- 0: Generic code: same on every make
- 5: Speed and idle
- 55: Specific fault in that system
Frequently asked questions
Can I keep driving with code P0555?
Drive without demanding power and go to a repair shop soon. If you see a lot of blue smoke or hear a metallic noise, shut off the engine.
What causes code P0555?
The most common causes are: connector or wire to the sensor open or corroded; sensor faulty; 5 V reference disturbed (short at another sensor on the same reference).
Related codes
- P0556Brake Booster Pressure Sensor Circuit Range/Performance
- P0557Brake Booster Pressure Sensor Circuit Low
- P0558Brake Booster Pressure Sensor Circuit High
- P0559Brake Booster Pressure Sensor Circuit Intermittent
- P0641Sensor Reference Voltage A Circuit/Open
Sources
- law.cornell.edu: 13 CCR 1968.2
- gsi.ext.gm.com: 18OBDG03A Engine Diagnostics
- gsi.ext.gm.com: 2006file10
Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.