P0256: Injection Pump Fuel Metering Control B Malfunction
The P0256 code indicates a malfunction in the fuel metering control circuit 'B' of the injection pump, which controls fuel delivery based on engine demand. This can be caused by a faulty fuel metering solenoid, wiring issues, or internal pump damage. The ECM detects an incorrect voltage or signal from the metering control, leading to improper fuel metering and potential drivability issues.
01. Most Common Causes
- Faulty fuel metering solenoid
- Open or shorted wiring in the metering control circuit
- Internal injection pump failure (cam, rotor, or injector)
- ECM software or hardware issue
02. Symptoms You Will Notice
- Engine hard to start or no start
- Loss of power or hesitation during acceleration
- Black smoke from exhaust
- Check Engine Light illuminated
03. Step-by-Step Diagnosis
Step 1: Scan for additional codes and freeze frame data.
Step 2: Visually inspect wiring and connectors for damage or corrosion.
Step 3: Test fuel metering solenoid resistance and voltage supply.
Step 4: Perform a fuel pressure test to verify pump output.
Step 5: If all else fails, replace the injection pump.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
No, driving with P0256 can cause poor performance, stalling, or engine damage. It's best to have it diagnosed and repaired promptly.
How much does it cost to fix?▼
Repair costs range from $200 to $800 depending on the cause. Replacing the injection pump is the most expensive option.