GM (from about model year 2017/18) monitors the brake booster with a vacuum sensor: with the pedal at rest and high intake vacuum the booster must hold its vacuum; a loss over time is filtered as a drift ratio, and above a threshold P050F sets, MIL after two trips. It runs with the engine on, during start-stop auto-stops and after switch-off. Without enough brake vacuum the module must throttle, restart the engine from auto-stop or request a pump – which affects idle and start-stop – and brake assistance can drop. Ford and FCA do not use P050F.
Low severity. Can I keep driving?You can keep driving, but check that the brake lights work: that part is a safety issue.
Symptoms
- Check engine light on
- Hard brake pedal, especially after auto-stop
- Hissing at the pedal, start-stop stops less often
Most likely causes
- Leaking vacuum hose or check valve
- Leaking diaphragm in the brake booster
- Vacuum sensor or its seal faulty
- Electric or mechanical vacuum pump weak (where fitted)
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: medium
- It affects emissions.
What each character of P050F means
- P: Powertrain: engine and transmission
- 0: Generic code: same on every make
- 5: Speed and idle
- 0F: Specific fault in that system
Frequently asked questions
Can I keep driving with code P050F?
You can keep driving, but check that the brake lights work: that part is a safety issue.
What causes code P050F?
The most common causes are: leaking vacuum hose or check valve; leaking diaphragm in the brake booster; vacuum sensor or its seal faulty.
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
- P0171System Too Lean Bank 1
Sources
- gsi.ext.gm.com: 18OBDG03A Engine Diagnostics
- gsi.ext.gm.com: 18OBDG04 Engine Diagnostics
- en.wikipedia.org: Vacuum servo
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.