P2E5B: Cylinder 3 Alternative Fuel Misfire Detected

What it means

Misfire detected on cylinder 3 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

While the engine uses alternative fuel, the controller detects misfires from changes in crankshaft rotation. P2E5B points specifically to cylinder 3, where restricted alternative-fuel injector flow or a poor injector connection can leave that cylinder without a reliable charge.

Common causes

Most likely first.

1. Injector clogged or weak
2. 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

1. Use a scan tool to check cylinder 3 misfire counts and the freeze-frame conditions when the alternative-fuel misfire occurred.
2. Compare cylinder 3 operation on petrol and alternative fuel to see whether the problem is limited to alternative-fuel mode.
3. Visually inspect cylinder 3's alternative-fuel injector, connector, and wiring for damage, corrosion, looseness, or leakage.
4. Check fuel quality and the alternative-fuel supply conditions, especially if symptoms started after a refill or occur under acceleration.
5. Test cylinder 3's alternative-fuel injector operation and delivery against the other cylinders and the manufacturer's specification.
6. If cylinder 3 also misfires on petrol, investigate its ignition and compression rather than assuming the alternative-fuel injector is the cause.

Common fixes

• Repair a damaged or poorly seated cylinder 3 injector connector or harness.
• Use known-good alternative fuel if the current fuel may be off-spec.
• Clean or replace the cylinder 3 alternative-fuel injector when testing confirms restricted or weak delivery.
• Repair a confirmed fault in alternative-fuel pressure regulation or supply.

Can I keep driving?

Avoid hard acceleration and stop if the check-engine light flashes or the engine becomes very rough, because ongoing misfire can damage the catalytic converter. If it runs smoothly on petrol, use that mode if available while arranging diagnosis.