What it means
The control module detects an intermittent fault in injection pump fuel metering control A. The fault may involve the control circuit or the metering control itself.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Injection-pump fuel metering control A regulates fuel delivery, and the control module monitors its command and feedback over time. P0255 sets when control A's signal or operation drops out intermittently rather than remaining consistently normal or faulty. Vibration or a loose connection can make the engine lose fueling briefly.
Common causes
Most likely first.
- Connector loose or corroded
- Connector with intermittent contact under vibration
- Harness routed against vibrating component
Symptoms
- Check-engine light on
- Intermittent rough running
- Intermittent loss of power
- Hard starting
How to diagnose it
- Save freeze-frame data and review pending codes and available live data to see whether the dropout coincides with vibration, engine movement, or a particular load.
- Inspect control A's connector for looseness, corrosion, damaged seals, or terminals that do not grip securely.
- Trace the harness to the injection pump and look for chafing, heat damage, or routing against a vibrating component.
- With the engine safely stationary, gently move the harness while watching scan data for a signal dropout; avoid hot or moving parts.
- Check circuit continuity and actuator response using the manufacturer's procedure, including conditions that may reproduce the intermittent fault.
Common fixes
- Secure a loose control A connector and clean or repair corroded terminals.
- Repair chafed wiring and reroute or secure the harness away from vibration and heat.
- Replace a control A actuator that intermittently fails testing.
- Repair the injection pump or module only if the intermittent circuit fault has been ruled out.
Can I keep driving?
If the engine is currently running normally, make only a short, gentle trip and avoid situations where a brief loss of power would be dangerous. Stop driving if it stalls or power cuts out repeatedly, since the fault may leave you unable to restart.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.