Code P0252: Injection Pump Fuel Metering Control “A” Circuit Malfunction
Complete guide to diagnosing and resolving the issue
1. What is code P0252?
P0252 is a generic OBD-II code related to the Injection Pump Fuel Metering Control “A” Circuit, commonly found on diesel vehicles (Ford, Chevy, Mercedes, VW, etc.). It indicates a range/performance problem in the fuel control system, often linked to the Fuel Rail Pressure (FRP) sensor or its electrical circuit.
Fuel Metering Circuit Operation
- The FRP sensor converts the amount of fuel delivered by the pump into an electrical signal for the PCM.
- The PCM uses this signal to regulate fuel injection based on engine demands.
- If the FRP signal falls outside expected parameters, the PCM stores code P0252.
2. Severity of Code P0252
- Mechanical failure (e.g., faulty injection pump): Severe (risk of stalling or engine damage).
- Electrical issue (e.g., short circuit): Moderate (PCM may partially compensate).
3. Common Symptoms
- Malfunction Indicator Lamp (MIL) illuminated.
- Decreased fuel economy.
- Occasionally: Rough idle or power loss.
4. Possible Causes
Electrical Problems
- Open or short circuit (to ground or voltage) in the FRP signal wire.
- Faulty power supply or ground to the FRP sensor.
- Corrosion in connectors or damaged wiring.
Mechanical/Electronic Failures
- Faulty FRP sensor (most likely cause).
- Failed fuel quantity actuator.
- Rare: PCM failure (check as last resort).
5. Troubleshooting Steps
Preliminary Checks
- Check Technical Service Bulletins (TSBs): A known fix may exist for your model.
- Visual inspection:
- Locate the FRP sensor (mounted on injection pump).
- Check connectors, wires, and terminals for corrosion, burn marks, or physical damage.
- Clean contacts with electrical spray and apply dielectric grease.
Electrical Tests
- Power and ground test:
- Disconnect FRP connector.
- Measure voltage between power terminal and ground (ignition ON).
- Expected: 5V or 12V (per manufacturer specifications).
- If out of range: Check power circuit or PCM.
- Signal wire test:
- Measure voltage at signal terminal (ignition ON).
- Expected: 5V.
- If abnormal: Repair wiring or replace PCM.
FRP Sensor Replacement
- If electrical tests are normal but code persists, replace the FRP sensor or fuel quantity actuator.
- Note: Some PCMs require reprogramming after replacement.
6. Conclusion
P0252 indicates a malfunction in the fuel metering circuit, often related to the FRP sensor. While basic checks (connectors, voltage) are DIY-friendly, professional diagnosis is recommended for advanced testing or PCM replacement. Ignoring this code may lead to increased fuel consumption or engine damage.
🔧 Tip: Use a vehicle-specific repair manual to accurately identify the “A” circuit and technical specifications.