OBD-II Code P0257 — What It Means & How to Fix It

What it means

P0257 means the injection pump fuel metering control signal on Bank B is reading lower than expected.
The engine computer isn't getting enough signal back from the Bank B metering solenoid.
This is exclusively a diesel engine code.
You may experience hard starting, lack of power, lean running on one bank, and rough idle.
Left unaddressed, under-fueling on one bank can cause uneven wear and engine damage over time.

Affected Models

All diesel vehicles 1996+
Common in V-engine diesel trucks
Common in Ford Power Stroke V8 diesels
Common in GM 6.6L Duramax diesel
Common in diesel engines with per-bank injection control

Common Causes

Open circuit or broken wire in the Bank B metering solenoid circuit
Metering solenoid on Bank B failed in the closed/low-fuel position
Corroded or high-resistance connector at the Bank B pump connection
Low fuel pressure preventing adequate solenoid operation
ECM failing to output sufficient signal voltage to Bank B

How to Fix It

Connect an OBD-II scanner and check for additional codes. Look especially for fuel pressure codes (P0191, P0192) which would suggest the fuel supply is starving the Bank B solenoid.

A fuel pressure problem often triggers codes on both banks — a Bank B-only code is more likely electrical.
Replace the fuel filter as a first step, especially if it's been over 20,000 miles since the last change. Low pressure from a restricted filter can cause low-signal codes on one or both banks.

Diesel filters are cheap.
Don't skip this step.
Inspect the Bank B wiring harness and solenoid connector. Use a multimeter to check for continuity from the ECM connector to the pump connector. An open circuit indicates a broken wire.

Look specifically for wire damage near the firewall, engine mounts, or anywhere the harness is clamped.
Test the resistance of the Bank B metering solenoid directly. A solenoid that's open internally (infinite resistance) won't work at all, causing a low-signal reading.

Compare the measured resistance to the spec in your service manual.
Out-of-spec resistance means a failed solenoid.
If all electrical checks pass, have the injection pump professionally tested. The Bank B metering valve may be mechanically stuck and not responding to the solenoid signal.

A diesel shop can test the pump on a bench and determine if solenoid replacement or full pump rebuild is needed.

When to Call a Professional

Per-bank injection diagnosis requires a diesel-capable scan tool with live data.
A general mechanic without diesel-specific tools cannot properly diagnose this code.
Seek a diesel specialist who can monitor Bank A and Bank B injection data simultaneously while driving.
If basic wiring checks don't reveal the problem, professional diagnosis is the only reliable next step.

Frequently Asked Questions

Can I drive with P0257?

Light driving on local roads is generally okay in the short term.
However, under-fueling on Bank B means those cylinders aren't performing properly.
Extended driving with this code active leads to uneven combustion stress and potential injector damage.
Prioritize getting it diagnosed within a week or two.

How do I know if it's a wiring problem or a pump problem?

Wiring problems usually cause sudden fault codes and may be intermittent.
Pump problems tend to develop gradually and may cause noticeable symptoms before the code sets.
A multimeter can quickly rule out wiring and connector issues.
If wiring is fine, the pump is the likely culprit.

How much does P0257 cost to fix?

Fuel filter: $50–$150.
Wiring or connector repair: $100–$400.
Bank B solenoid: $200–$700.
Full pump replacement: $1,000–$2,500 installed.
Always start with the cheapest and most accessible checks first.