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.
Medium severity. Can I keep driving?You can drive in moderation without pushing the engine. If you hear knocking, avoid full-throttle acceleration.
Cylinder 3 is numbered according to the manufacturer: check your engine's manual before working on it.
Symptoms
- Check engine light on
- Pinging under acceleration
- Noticeably less power
Most likely causes
- Carbon build-up or a hot spot in cylinder 3
- Injector of cylinder 3 delivering too little (lean, hot combustion)
- Engine damage from casting sand or chips (Stellantis 2.0L PHEV)
- Knock sensor loose or wrongly torqued, picking up noise
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: hard
- It affects emissions.
What each character of P2338 means
- P: Powertrain: engine and transmission
- 2: Generic code: same on every make
- 3: Ignition and misfires
- 38: Specific fault in that system
Frequently asked questions
Can I keep driving with code P2338?
You can drive in moderation without pushing the engine. If you hear knocking, avoid full-throttle acceleration.
What causes code P2338?
The most common causes are: carbon build-up or a hot spot in cylinder 3; injector of cylinder 3 delivering too little (lean, hot combustion); engine damage from casting sand or chips (Stellantis 2.0L PHEV).
Related codes
- P2336Cylinder 1 Above Knock/Combustion Vibration Sensor Threshold
- P2337Cylinder 2 Above Knock/Combustion Vibration Sensor Threshold
- P2339Cylinder 4 Above Knock/Combustion Vibration Sensor Threshold
- P0324Knock/Combustion Vibration Control System Error
- P0327Knock/Combustion Vibration Sensor A Circuit Low
- P0303Cylinder 3 Misfire Detected
Sources
- static.nhtsa.gov: MC 11032844 0001
- saabwisonline.com: dtc p0324 p0326 p0331 p06b6 or p06b7
- en.wikipedia.org: Engine knocking
- law.cornell.edu: 13 CCR 1968.2
Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.