Powertrain, generic (extended)

P2E5B Cylinder 3 Alternative Fuel Misfire Detected

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

P2E5B flags misfire on cylinder 3 during operation on CNG or LPG; on petrol the matching code is P0303. No manufacturer publishes P2E5B. One cause that belongs to gas engines in particular is valve seat wear: dry gaseous fuels leave few combustion products, so valve and seat insert rub metal on metal and the seat recedes, as a Honda patent on seat materials explains. Once a valve stops sealing, compression in that cylinder falls and combustion becomes unreliable. For this reason natural-gas engines usually carry hardened exhaust valves and seats, and Ford's 2014 F-150 gaseous-fuel prep package added hardened valves, seats, pistons and rings. A compression or leak-down test on cylinder 3 separates this from injector or ignition faults; engines converted without hardened parts deserve extra suspicion.

Likely causes

Faulty gas injector on cylinder 3
Valve seat recession on cylinder 3 from dry gas operation, valve no longer seals
Worn plug or failing coil on cylinder 3
Retrofit gas conversion on an engine without hardened valves and seats

Symptoms

  • Misfire on gas that slowly gets worse, later also on petrol
  • Low compression on cylinder 3, sometimes a ticking valve noise
  • Check engine light

Repair estimate

DifficultyHardWorkshop job
Parts and labour€100–2,500
Time0–12 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

alt fuel injector cyl 3ignition coil cyl 3

Related codes

P2E58P0303P2E5AP2E5CP0203

References: law.cornell.edu, image-ppubs.uspto.gov, afdc.energy.gov, government-fleet.com.