What it means
Misfire detected on cylinder 4 during alternative fuel operation. Specific to bi-fuel CNG/LPG operation.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
- The engine or gearbox may go into limp mode
How it works
The engine controller monitors crankshaft speed to detect incomplete combustion while running on alternative fuel. This code identifies cylinder 4 as the misfiring cylinder, directing attention to cylinder 4's alternative-fuel injector, wiring, and fuel delivery.
Common causes
Most likely first.
- Injector clogged or weak
- Fuel quality off-spec
Symptoms
- Check engine light on or flashing
- Rough idle and uneven running
- Power loss, hesitation under acceleration
- Increased fuel consumption
- Possible smell of unburned fuel from exhaust
How to diagnose it
- Review freeze-frame data and cylinder-specific misfire counts to verify that cylinder 4 misfires during alternative-fuel operation.
- Check whether the misfire disappears on petrol; that comparison helps distinguish alternative-fuel delivery trouble from a fault affecting both modes.
- Inspect cylinder 4's alternative-fuel injector and its connector and wiring for loose pins, corrosion, damage, or leakage.
- Consider recent refuelling and check alternative-fuel quality and supply conditions, including whether the symptom appears under load.
- Test cylinder 4's injector operation and delivery, comparing it with the other cylinders and the manufacturer's specification.
- If cylinder 4 misfires on petrol too, check its ignition components and mechanical condition.
Common fixes
- Repair damaged or corroded wiring at the cylinder 4 alternative-fuel injector.
- Refill with known-good alternative fuel if fuel quality is suspect.
- Clean or replace the cylinder 4 alternative-fuel injector if it is confirmed weak or restricted.
- Correct a verified alternative-fuel supply or pressure-regulation problem.
Can I keep driving?
Do not continue driving with a flashing check-engine light or severe rough running; misfire can overheat and damage the catalytic converter. If petrol mode runs smoothly, use it if available and have the cylinder 4 fault diagnosed soon.
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.