What it means
Ion current from cylinder 5 is below the expected window. Spark plug fouled, signal wire shorted to ground, or sensing path interrupted.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The ECM reads ion current through the spark plug after combustion to assess cylinder 5. This code sets when cylinder 5's signal is below its expected range, which can result from a fouled plug or a problem pulling the sense signal toward ground.
Common causes
Most likely first.
- Spark plug fouled with carbon or oil
- Sense wire shorted to ground
- Connector pins corroded - high contact resistance
Symptoms
- Check-engine light on
- Rough idle or engine misfire
- Reduced engine performance
How to diagnose it
- Check freeze-frame and live data for a low cylinder 5 ion-current reading and note whether rough running or a misfire occurs at the same time.
- Inspect cylinder 5's spark plug for carbon or oil fouling, which can weaken the ion-current signal.
- Inspect cylinder 5's sense-wire routing and connector for a short to ground, damaged insulation, corrosion, or poor pin contact.
- With the circuit safely isolated as specified by the manufacturer, test the cylinder 5 sense wire for continuity and unwanted connection to ground.
- Check the cylinder 5 sensing path and module output against the manufacturer's specification if the plug and wiring are sound.
Common fixes
- Replace a carbon- or oil-fouled cylinder 5 spark plug and address any evident source of contamination.
- Clean and secure corroded cylinder 5 connector pins.
- Repair or replace cylinder 5 sense wiring shorted to ground or otherwise damaged.
- Replace a failed cylinder 5 sensing element or module if testing confirms an internal fault.
Can I keep driving?
Avoid extended driving or heavy loads while cylinder 5 is misfiring, since unburned fuel can overheat the catalytic converter. If the engine shakes severely or the warning light flashes, stop driving and arrange diagnosis.
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.