Powertrain, generic (extended)

P229A Fuel Pressure Regulator B Exceeded Control Limits - Pressure Too Low

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

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.

Likely causes

Rail pressure regulator valve leaking internally
High-pressure pump delivering too little
Excessive injector leak-off
Restricted low-pressure supply or clogged filter

Symptoms

  • Check engine light
  • Lack of power under load
  • Longer cranking times

Repair estimate

DifficultyHardWorkshop job
Parts and labour€150–2,500
Time1–5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

fuel pressure regulator

Related codes

P229BP228CP228BP2293P0087

References: gsi.ext.gm.com, law.cornell.edu.