P2340 code meaning
Cylinder 5 Above Knock/Combustion Vibration Sensor Threshold
Powertrain system Generic code P23xx codes Check engine light
What P2340 means
P2340 reports knock above threshold for cylinder 5, so it can only occur on engines with at least five cylinders – inline-five, six-cylinder, V8 or larger. The principle matches the rest of the series: the module evaluates the knock sensor signal in the crank-angle window of each combustion and retards spark individually when one cylinder knocks. No manufacturer was found that documents P2340 publicly; the Stellantis bulletin for P2336–P2339 concerns a four-cylinder engine and therefore stops at cylinder 4. GM and Saab detect the same condition but store P0324 (excessive knock on a single cylinder for more than 8 s). Causes are usually local to cylinder 5: deposits, a lean injector, a wrong plug or internal damage; poor fuel would affect several cylinders.
P2340 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium
- Typical labor0.5 to 8 hours
- Clears after repairAfter a drive cycle
Symptoms of P2340
- Check engine light on
- Pinging or knocking under load
- Less power, higher consumption
Common causes of P2340
- PossibleCarbon deposits or glowing particles in cylinder 5
- PossibleInjector of cylinder 5 delivering too little
- Less likelyWrong heat range or damaged spark plug
- Less likelyMechanical damage in cylinder 5 (piston, valve)
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Knock sensorCylinder 5
What each part of P2340 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. |
| 40 | The exact fault in that area. |
What to do next
- Note P2340 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 P2340
What does P2340 mean?
P2340 means "Cylinder 5 Above Knock/Combustion Vibration Sensor Threshold". P2340 reports knock above threshold for cylinder 5, so it can only occur on engines with at least five cylinders – inline-five, six-cylinder, V8 or larger. It is a generic code, so it means the same on every make.
Is it safe to drive with P2340?
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 P2340 fail an emissions test?
Yes, it can. P2340 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 P2340 to fix?
Difficulty: medium. A typical repair takes 0.5 to 8 hours of work. This is a job for a workshop.
Will P2340 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.