P0555 code meaning
Brake Booster Pressure Sensor Circuit
Powertrain system Generic code P05xx codes Check engine light
What P0555 means
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.
P0555 at a glance
- Check engine lightYes, usually on
- Emissions testNot an emissions code
- Limp modeNot expected
- Repair difficultyMedium, DIY possible
- Typical labor0.5 to 1.5 hours
- Clears after repairAfter a drive cycle
Symptoms of P0555
- Check engine light or brake booster warning
- Stop-start inactive
- Often no change in driving
Common causes of P0555
- Most likelyConnector or wire to the sensor open or corroded
- PossibleSensor faulty
- Possible5 V reference disturbed (short at another sensor on the same reference)
- Less likelyEngine module
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Brake booster pressure sensorSensor wiringEngine control module
What each part of P0555 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 5 | Area: vehicle speed, idle control and auxiliary inputs. |
| 55 | The exact fault in that area. |
What to do next
- Note P0555 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0555
What does P0555 mean?
P0555 means "Brake Booster Pressure Sensor Circuit". The brake booster pressure sensor (5 V reference, signal, ground) measures the vacuum in the brake booster. It is a generic code, so it means the same on every make.
Is it safe to drive with P0555?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P0555 fail an emissions test?
P0555 is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is P0555 to fix?
Difficulty: medium. A typical repair takes 0.5 to 1.5 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P0555 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.