P2338 code meaning
Cylinder 3 Above Knock/Combustion Vibration Sensor Threshold
Powertrain system Generic code P23xx codes Check engine light
What P2338 means
P2338 sets when the knock signal assigned to cylinder 3 rises above its threshold. Because one or two knock sensors serve several cylinders, the module relies on the crank-angle window to tell which cylinder knocked; a code for just one cylinder therefore suggests something local: carbon build-up, a hot spot, a lean-running injector, a wrong spark plug, or mechanical noise that happens to fall into that window. Low-octane fuel tends to raise knock on every cylinder. Stellantis names P2338 with P2336, P2337 and P2339 in bulletin 09-009-26, which covers the 2.0L PHEV engine in Wrangler 4xe and Grand Cherokee 4xe models from Jeep, where foundry sand and machining chips are the cause and the engine is exchanged. Persistent knock can hole or melt pistons, so it should not be ignored.
P2338 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyHard
- Typical labor0.5 to 13 hours
- Clears after repairAfter a drive cycle
Symptoms of P2338
- Check engine light on
- Pinging under acceleration
- Noticeably less power
Common causes of P2338
- PossibleCarbon build-up or a hot spot in cylinder 3
- PossibleInjector of cylinder 3 delivering too little (lean, hot combustion)
- PossibleEngine damage from casting sand or chips (Stellantis 2.0L PHEV)
- Less likelyKnock sensor loose or wrongly torqued, picking up noise
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Knock sensorSpark plug
What each part of P2338 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 3 | Area: ignition system or misfire. |
| 38 | The exact fault in that area. |
What to do next
- Note P2338 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P2338
What does P2338 mean?
P2338 means "Cylinder 3 Above Knock/Combustion Vibration Sensor Threshold". P2338 sets when the knock signal assigned to cylinder 3 rises above its threshold. It is a generic code, so it means the same on every make.
Is it safe to drive with P2338?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P2338 fail an emissions test?
Yes, it can. P2338 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P2338 to fix?
Difficulty: hard. A typical repair takes 0.5 to 13 hours of work. This is a job for a workshop.
Will P2338 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.