P233CFuel Pressure Regulator C Control Circuit High
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- 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.
- What you may notice
- Check engine light on immediately
- Long cranking or no start
- Reduced power, sometimes stalling
- Likely causes
- LikelyControl wire chafed against a battery-fed wire in the harness
- PossibleDamaged valve connector with pins touching
- RareShorted turns in the metering valve coil
- RareLow-side driver in the engine control module faulty
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €60 – €900
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.