P229AFuel Pressure Regulator B Exceeded Control Limits - Pressure Too Low
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- P229A is the low-pressure control-limit check for fuel pressure regulator B. In GM's 2018 diesel table regulator B is the rail pressure regulator valve; while it governs the rail in closed loop, the ECM compares setpoint and measured pressure and flags a deficit beyond about 13 MPa, using the same 640-of-800-sample window and Type B rating as the metering unit check P228C. The test pauses at low fuel level, ambient pressure under 60 kPa or ambient temperature below −7 °C. A valve that no longer seals, internal injector leakage or a pump short of delivery create the deficit. GM is the only maker found documenting P229A publicly. P229B is the overpressure case, P228B the stage that forces a shutdown.
- What you may notice
- Check engine light
- Lack of power under load
- Longer cranking times
- Likely causes
- LikelyRail pressure regulator valve leaking internally
- PossibleHigh-pressure pump delivering too little
- PossibleExcessive injector leak-off
- RareRestricted low-pressure supply or clogged filter
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Hard · Usually a job for a workshop.Typical cost: €150 – €2,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.