Powertrain, generic (extended)

P229C Fuel Pressure Regulator B Exceeded Learning Limits - Too Low

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

P229C means the learned correction for fuel pressure regulator B has reached its lower bound. No manufacturer documents this code publicly. The matching check for regulator A is described by Ford for its 2023 diesels: the controller adapts at steady rail pressure of 600 bar or more and stores P228E or P228F when the adaptation would exceed roughly a 20 % sensor-slope error. On systems with two regulators, such as GM diesels with a pump metering unit (A) and a rail pressure valve (B), the B value describes the learned behaviour of that spill valve. CARB requires a monitor to report a pressure control that has used up its adjustment authority. Expect a lit MIL with little drivability effect; P229D is the upper bound.

Likely causes

Rail pressure regulator valve characteristic drifted
Rail pressure sensor characteristic drifted
Adaptation values not reset after a component replacement

Symptoms

  • Check engine light
  • Usually no noticeable change in driving

Repair estimate

DifficultyHardWorkshop job
Parts and labour€100–1,500
Time0.5–4 h

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

Parts involved

fuel pressure regulator

Related codes

P229DP228EP229AP2293

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