What it means
The ion current signal from cylinder 1 is outside the expected range for combustion conditions. Combustion quality cannot be assessed reliably.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The ECM evaluates the ion-current signal for cylinder 1 to judge combustion after the spark. This code sets when that signal falls outside the expected range for the operating conditions, even if a signal is present, so the ECM cannot assess cylinder 1 combustion reliably.
Common causes
Most likely first.
- Spark plug aged — electrode shape changed
- Ion sense circuit gain drift
- Sensor element aged beyond calibration window
Symptoms
- Check-engine light on
- Rough idle or engine misfire
- Reduced engine performance
How to diagnose it
- Record freeze-frame data and check live misfire counts for cylinder 1 under the conditions when the code set.
- Inspect the cylinder 1 spark plug for wear, deposits, or electrode damage, since plug condition can change the ion-current signal.
- Check cylinder 1's ignition and ion-sense wiring and connectors for damage, corrosion, loose pins, or poor routing.
- Use the manufacturer's wiring diagram and procedure to test the cylinder 1 sensing path and compare its signal with the specified range.
- If the plug and wiring are sound, test the ion-sense circuit gain and sensor or module response using the manufacturer's procedure.
Common fixes
- Replace an aged or damaged cylinder 1 spark plug with the specified type.
- Repair poor connections or damaged wiring in the cylinder 1 ion-sense circuit.
- Replace a failed or out-of-calibration ion-sense component if testing confirms it.
- Correct any cylinder 1 combustion fault found during diagnosis.
Can I keep driving?
If the engine runs smoothly, limit driving and arrange diagnosis soon because a persistent misfire can damage the catalytic converter. Stop driving if misfire becomes severe, power drops noticeably, or the warning light flashes.
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.