Powertrain, generic (extended)

P233C Fuel Pressure Regulator C Control Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

With P233C the ECM sees the control line of fuel pressure regulator C pulled towards battery voltage. GM's 2025 diesel table 25OBDG04B runs this test while the low-side driver of the second metering unit valve is switched on: if the voltage across the driver stays high, the line evidently has a path to power of less than about 0.5 Ohm. The check samples every 100 ms with system voltage above 11 V and is Type A, lighting the MIL in the first trip. Because the driver can then no longer pull current through the coil, the valve stays without power and the ECM loses part of its control over high-pressure delivery; hard starting or reduced power can follow. GM bulletin 21-NA-149 lists the code for the 3.0L LM2 diesel with chafed harnesses. P233B is the ground-short counterpart.

Likely causes

Control wire chafed against a battery-fed wire in the harness
Damaged valve connector with pins touching
Shorted turns in the metering valve coil
Low-side driver in the engine control module faulty

Symptoms

  • Check engine light on immediately
  • Long cranking or no start
  • Reduced power, sometimes 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

P233AP233BP2C00P0092P2296

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