What it means
The ECM detects that the injection pulse on cylinder 1 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 1 and evaluates whether the resulting combustion matches expectations. This code indicates that cylinder 1's injection-pulse performance differs from the expected result, which can reflect 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 data to confirm that cylinder 1 is the outlier under the conditions that set the code.
- Inspect the cylinder 1 injector connector and wiring for looseness, damage, corrosion, or signs of fuel leakage.
- Compare cylinder 1's injection-pulse data and combustion contribution with the other cylinders at idle and under the conditions recorded in freeze-frame data.
- Check fuel quality and whether the fault appeared after refuelling, then assess whether the symptom affects multiple cylinders or mainly cylinder 1.
- If wiring and fuel are not the cause, test cylinder 1 injector operation and flow using the manufacturer's procedure before replacing parts.
Common fixes
- Correct contaminated or unsuitable fuel if the problem began after a fuel change.
- Reconnect or repair the cylinder 1 injector connector and wiring.
- Clean or service the fuel system if testing identifies a fuel-quality or contamination issue.
- Replace the cylinder 1 injector if its measured performance is outside the manufacturer's specification.
Can I keep driving?
A mild rough idle may allow a short, gentle trip, but avoid hard acceleration if power is reduced. Stop driving if the engine shakes severely, the warning light flashes, or it begins misfiring badly, since continued operation 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.