What it means
The ECM detects that the injection pulse on cylinder 4 does not produce the expected combustion result. Pulse width, timing, or quantity drift compared to the bank average.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The engine control module adjusts the injection pulse for cylinder 4 and checks whether combustion responds as expected. This code means cylinder 4's injection-pulse performance differs from the expected result, potentially due to injector flow drift or fuel affecting combustion.
Common causes
Most likely first.
- Injector aged - flow characteristic drifted
- Fuel quality affecting injection result
Symptoms
- Check-engine light may be on
- Rough idle or engine vibration
- Hesitation or reduced power
How to diagnose it
- Save freeze-frame data and check cylinder-specific misfire or contribution information to confirm whether cylinder 4 is the outlier.
- Inspect the cylinder 4 injector connector and wiring for corrosion, loose pins, damage, or signs of fuel leakage.
- Compare cylinder 4 injection-pulse data and combustion contribution with the other cylinders at idle and under the recorded operating conditions.
- Check fuel quality and recent refuelling history, noting whether similar symptoms or data changes affect other cylinders.
- If fuel and wiring checks pass, test cylinder 4 injector operation and flow according to the manufacturer's procedure.
Common fixes
- Correct unsuitable or contaminated fuel if it coincides with the fault.
- Reconnect or repair the cylinder 4 injector connector and wiring.
- Resolve fuel contamination if testing shows it is affecting injector performance.
- Replace the cylinder 4 injector if testing finds its flow or operation outside specification.
Can I keep driving?
If the engine is running smoothly, limit driving to short, gentle trips. Stop if it shakes badly, loses substantial power, or the warning light flashes, because continued misfire can damage the catalytic converter.
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.