Injection Pump Fuel Metering Control A Malfunction (Cam/Rotor/Injector)
The P0251 code means the vehicle's onboard diagnostic system has detected: Injection Pump Fuel Metering Control A Malfunction (Cam/Rotor/Injector). This is a serious severity code.
- Keep driving?
- Short distances only
- DIY difficulty
- hard
- Estimated cost
- $50 - $4,000+ (a fuel filter or supply-side restriction at the low end; wiring or connector repair in the middle; injection pump replacement at the top)
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Common Symptoms
- Check Engine Light on
- Hard starting or long cranking
- Rough running, low power, possible stalling
- Possible smoke on diesels
Probable Causes (Ranked by Likelihood)
- Injection pump fuel metering fault (cam/rotor/injector control) High
- Low fuel supply to the pump — filter, lift pump, restriction High
- Wiring or connector fault to the pump's metering control Moderate
- Failing injection pump Moderate
Frequently Asked Questions
What does P0251 mean?
The engine computer detected a malfunction in the injection pump's fuel metering control — the mechanism (cam, rotor, or injector control depending on pump design) that decides how much fuel is delivered. It is a diesel code; check fuel supply and wiring before suspecting the pump itself, because a starved or poorly connected pump sets the same code.
Is this the wastegate code some sites list?
No. P0251 is sometimes mislabeled as a turbo wastegate solenoid code, but the wastegate solenoid codes are the P0243-P0249 range. P0251 opens the injection pump fuel metering block (P0251-P0260), which is why it appears on diesel trucks and equipment rather than turbocharged gas cars.
Mechanics Guide Step-by-step diagnosis
Step-by-Step Diagnostic Procedure
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This is a DIESEL injection-pump code: the computer cannot control fuel metering as commanded.
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Check the low-pressure supply first — fuel filter and lift pump. A starved pump sets metering faults while itself being healthy.
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Inspect wiring and connectors to the pump's metering control before condemning the pump.
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Injection pump replacement is the last step, not the first — supply and wiring faults produce identical codes.
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Meaning corroborated against this site's independently researched diesel-family pages for the same code (Duramax, Hino, Isuzu, Power Stroke — 4 independent families).
Sources 2
This page is built from documented references. Verify against your own service info before repair work.
- SAE J2012Diagnostic Trouble Code Definitions (defines the generic OBD-II code ranges)
- Cross-checked against the SAE J2012:2002 DTC table (2026-08-27)archived scan of the SAE standard — readable copy, not SAE’s current edition
P0251 on Diesel, EV & Equipment
The same code ID appears across other engines and platforms. The diagnostic flow varies by manufacturer — these are the platform-specific breakdowns:
Commonly Affected Vehicles
- Diesel engines with electronically metered injection pumps
Related Codes
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