Injection Pump Fuel Metering Control A Malfunction
The P0251 code indicates a malfunction in the injection pump fuel metering control circuit, specifically related to the cam, rotor, or injector components. This typically occurs in diesel engines with rotary injection pumps. The Engine Control Module (ECM) detects an abnormal signal from the fuel metering control system, which can lead to improper fuel delivery, affecting engine performance and emissions.
1. Most Common Causes
- Faulty fuel metering control valve (IMV/FCA) on the injection pump
- Worn or mechanically damaged injection pump rotor
- Faulty rotor position sensor or injector camshaft position sensor
- Open, shorted, or high-resistance wiring in the pump control circuit
- Corroded or loose electrical connections in the injection pump harness
- Internal injection pump failure (worn mechanical components)
- Malfunctioning injection pump control module (pump ECU)
2. Symptoms You Will Notice
- Engine hard to start or no start
- Loss of power and poor acceleration
- Excessive smoke from exhaust (black or white)
- Engine misfire or rough idle
3. Step-by-Step Diagnosis
Step 1: Scan for additional codes and check freeze frame data.
Step 2: Inspect wiring and connectors to the injection pump metering control actuator.
Step 3: Test the fuel metering control actuator resistance and voltage per manufacturer specs.
Step 4: Perform a fuel pressure and volume test to rule out fuel supply issues.
Step 5: If electrical tests pass, suspect internal pump failure and consult a diesel specialist.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
No, it is not safe. The vehicle may experience sudden loss of power or stalling, which can be dangerous. Have it diagnosed and repaired promptly.
How much does it cost to fix?▼
Diagnosis typically costs $50-$150. Repair costs vary widely: if the injection pump needs replacement, it can range from $1,000 to $3,000 or more, depending on the vehicle.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.