Fuel and air

P0259 — Injection Pump Fuel Metering Control 'B' Circuit High

Severity: medium Drive with care, to a shop

What P0259 means

A diesel ECM controls how much fuel the injection pump delivers through a metering solenoid or actuator. P0259 is set when voltage in control circuit 'B' reads higher than expected, for example from a short to power or a faulty actuator. The ECM then cannot meter fuel accurately.

Symptoms

  • Check Engine light on
  • Rough idle or misfire
  • Reduced power or hesitation
  • Higher fuel consumption
  • More exhaust smoke
  • Stalling or hard starting

Possible causes

  1. Faulty fuel metering solenoid or actuator on the injection pump
  2. Damaged wiring: short to voltage, open circuit or corroded terminals
  3. Poor connection at the pump or ECM connector
  4. Contaminated or poor-quality fuel affecting the metering valve
  5. Failed ECM (uncommon)

How to diagnose

  1. Read all codes and freeze frame data, clear the code and see if it returns
  2. Inspect the pump harness and connector for chafing, corrosion, heat damage or moisture
  3. Test circuit 'B' with a multimeter: supply voltage, no short to power, wire continuity and ground
  4. Measure the metering solenoid resistance and compare it with specification
  5. Check fuel pressure against the commanded value on a scan tool
  6. Review fuel correction values and cylinder balance data
  7. Check fuel quality and the condition of the fuel filters
  8. If wiring and solenoid are good, test the ECM and reprogram or replace it if needed

Common fixes

  • Repair or replace damaged wiring and connectors in circuit 'B'
  • Replace the pump metering solenoid or actuator
  • Replace contaminated fuel and filters
  • Replace or reprogram the ECM if confirmed faulty

Questions and answers

What does P0259 mean?

The ECM detected high voltage in the injection pump fuel metering 'B' circuit. Wiring faults and a bad metering solenoid are the most common causes.

Can I drive with P0259?

Only briefly and carefully, such as to a repair shop. The engine may lose power or stall, which is dangerous in traffic.

How do I fix P0259?

Start by checking the pump harness and connector, then the metering solenoid and circuit power. Replace the ECM last, only after everything else tests good.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.