Injection Pump Fuel Metering Control B Circuit High
The P0259 code indicates that the Engine Control Module (ECM) has detected a high voltage signal from the fuel metering control circuit B of the injection pump. This circuit controls the amount of fuel delivered by the pump, and a high voltage reading suggests a short to power, a faulty actuator, or an internal pump failure. This can lead to excessive fuel delivery, causing rich running, poor fuel economy, and potential engine damage.
1. Most Common Causes
- Short to battery voltage in the signal or power wire of the fuel metering solenoid 'B'
- Faulty fuel metering solenoid/actuator 'B' (open or internally shorted coil)
- Damaged, corroded, or loose terminals in the actuator connector
- Internal failure of the PCM driver (control transistor)
- Mechanical issues in the injection pump causing abnormal electrical feedback
2. Symptoms You Will Notice
- Check Engine Light illuminated
- Engine running rough or misfiring
- Excessive black smoke from exhaust
- Poor fuel economy
- Hard starting or no start
3. Step-by-Step Diagnosis
Step 1: Scan for additional codes and record freeze frame data.
Step 2: Visually inspect the injection pump wiring and connector for damage, corrosion, or shorts.
Step 3: Test the fuel metering actuator resistance and voltage supply per manufacturer specs.
Step 4: Check for short to power or ground in the FCA circuit using a multimeter.
Step 5: If wiring is okay, test the FCA by applying battery voltage and observing movement (if accessible).
Step 6: If FCA fails, replace it; if pump internal failure, replace or rebuild injection pump.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
No, it is not safe. The high voltage can cause excessive fuel delivery, leading to engine damage, poor performance, and potential stalling. Have the vehicle towed to a repair shop.
How much does it cost to fix?▼
Costs vary widely: replacing the fuel metering actuator can be $200-$400, while a new injection pump can cost $800-$2000 or more, plus labor.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.