Powertrain, generic (extended)

P233A Fuel Pressure Regulator C Control Circuit/Open

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

Fuel pressure regulator C is a third pressure actuator that only a few high-pressure systems have; which valve carries the letter is up to the manufacturer. GM's 2025 diesel table 25OBDG04B assigns C to a second fuel metering unit valve on the pump, driven by the ECM through a high-side and a low-side switch. P233A is logged when, with the valve commanded on, almost no current flows between the two drivers, i.e. the loop resistance looks higher than 200 kOhm; samples are taken every 100 ms above 11 V system voltage, and the fault is Type A, so the MIL comes on in the first trip. GM bulletin 21-NA-149 lists P233A for the 3.0L LM2 Duramax among codes caused by a chafed engine harness. P233B and P233C cover shorts; delivery can falter while the valve is dead.

Likely causes

Valve connector loose, corroded or a terminal pushed back
Engine harness wire broken where it rubs on brackets or clamps
Coil of the metering valve interrupted
Output driver in the engine control module faulty

Symptoms

  • Check engine light on in the first trip
  • Rail pressure deviates, hesitation or reduced power
  • Possibly hard starting or stalling

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€60–900
Time0.5–3 h

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

Parts involved

fuel pressure regulator chigh pressure fuel pumpwiring harness

Related codes

P233BP233CP2C00P0090P2294

References: gsi.ext.gm.com, static.nhtsa.gov, law.cornell.edu.