P2339 OBD-II Trouble Code: Cylinder #4 Above Knock Threshold

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P2339 is a diagnostic trouble code (DTC) for "Cylinder #4 Above Knock Threshold". This can happen for multiple reasons and a mechanic needs to diagnose the specific cause for this code to be triggered in your situation. Our certified mobile mechanics can come to your home or office to perform the Check Engine Light diagnostic. Once we are able to diagnose the problem, you will be provided with an upfront quote for the recommended fix and receive $20.00 off as a credit towards the repair. All our repairs are backed by our 12-month / 12,000-mile warranty.

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P2339 code definition

The P2339 trouble code indicates that a voltage level read from the knock sensor for engine cylinder 4 has been reported falling over the voltage limits outlined by the manufacturer.

What the P2339 code means

An engine's knock sensor detects vibrations caused by the engine being physically knocked. This will affect the It may be found on the engine block, intake manifold or the engine cylinder head. The knock sensor will record physical disturbances by varying voltage levels and feed the data into the vehicle's Powertrain Control Module (PCM). A P2339 will be registered in the vehicle's computer if the knock sensor detects an abnormally high amount of shock to engine cylinder 4.

What causes the P2339 code?

Although a faulty knock sensor is sometimes the case for a P2339 trouble code, if the sensor received a higher-than-normal voltage, a real engine problem is likely. The exact cause of the engine trouble should be evident by the other trouble codes that come alongside the P2339. The P2339 can also be the result of wiring concerns; broken, faulty or corroded wiring or connectors can ruin the knock sensor's electrical circuit, thereby feeding an inaccurate voltage input signal to the PCM.

What are the symptoms of the P2339 code?

In the case of a P2339 code, the engine may suffer from a general lack of power and experience problems with acceleration. The P2339 can be identified easily with the trouble code on the vehicle computer, as well as the illuminated dashboard trouble lamp. These symptoms are for purely diagnostic purposes only. In addition, because a P2339 indicates a potential malfunction in an engine-related sensor, the service engine lamp on the dashboard may act erratically until the issue is fixed.

How does a mechanic diagnose the P2339 code?

The P2339 code may be first identified by using an OBD-II code reader to scan the code. If there aren't any discernable issues with the engine itself, it is reasonable to suspect a faulty sensor. However, in the majority of cases, the P2339 code will come alongside other trouble codes relating to the engine. These other engine-based codes should be addressed before looking at the knock sensor. If all other engine issues are fixed, the P2339 should go away on its own. Nonetheless, all electrical wiring related to the knock sensor should be inspected for potential issues, including corrosion, disconnection and general damage.

Common mistakes when diagnosing the P2339 code

When a P2339 trouble code is reported, the engine's knock sensor is sometimes mistakenly reported as faulty. If the knock sensor has reported an issue, it is quite possible that the issue is real. Faulty knock sensors are known to occur, by replacing a sensor mistakenly will waste resources without doing anything to solve the root problem.

How serious is the P2339 code?

Due to the fact that the knock sensor is used to report potentially serious issues with the engine, a knock sensor code is most often a subsequent effect of an engine problem. Although the P2339 code is known to cause acceleration issues on its own, its accompanying trouble codes are usually what define its severity as an issue.

What repairs can fix the P2339 code?

  • Other trouble codes relating to the engine's performance should be solved before dealing with the knock sensor, provided others have been reported.

  • If there is nothing else wrong with the vehicle's engine system, suspect a faulty knock sensor. If the knock sensor is faulty, replace it as needed.

  • Replace any other engine-related components you have identified as being worn out or faulty. Any disconnected, broken or otherwise faulty electrical wiring should be replaced.

  • Once you have completed your repairs to the vehicle, give it a test drive. This will let you know whether the problem has been solved permanently or not. Recheck the computer afterwards to see if the code has returned or not.

Additional comments for consideration regarding the P2339 code

Some models and manufacturers will require the vehicle report the issue over the course of multiple drive cycles before the trouble code is officially logged.

Need help with a P2339 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701- 6230.

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Lincoln Aviator - Check Engine Light is on - San Antonio, Texas
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