P2338 OBD-II Trouble Code: Cylinder #3 Above Knock Threshold

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Cost of diagnosing the P2338 code

P2338 is a diagnostic trouble code (DTC) for "Cylinder #3 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 for $70.00. Once we are able to diagnose the problem, you will be provided with an upfront quote for the recommended fix and receive $30.00 off as a credit towards the repair. All our repairs are backed by our 12-month / 12,000-mile warranty.

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P2338 Code Definition

A P2338 code is a generic powertrain code related to an ignition-related problem, such as an engine misfire. It appears when the engine control module (ECM) has received a voltage reading outside the allowed variances from engine cylinder number three.

The P2338 code may be related to:

  • P0324: Knock Control System Error
  • P2336: Cylinder #1 Above Knock Threshold
  • P2337: Cylinder #2 Above Knock Threshold
  • P2339: Cylinder #4 Above Knock Threshold
  • P2340: Cylinder #5 Above Knock Threshold
  • P2341: Cylinder #6 Above Knock Threshold
  • P2342: Cylinder #7 Above Knock Threshold
  • P2343: Cylinder #8 Above Knock Threshold
  • P2344: Cylinder #9 Above Knock Threshold
  • P2345: Cylinder #10 Above Knock Threshold
  • P2346: Cylinder #11 Above Knock Threshold
  • P2347: Cylinder #12 Above Knock Threshold

What the P2338 Code Means

A knock sensor is a one-wire sensor that helps the engine control module (ECM) “hear” engine noise to help determine proper function through the use of a low-voltage signal. When the ECM receives a voltage reading from the knock sensor in cylinder 3 that varies 10% or more from the set voltage parameters, a P2338 code will be stored. If an abnormal reading is received by the ECM, it can adjust engine timing to reduce possible damage.

What Causes the P2338 Code?

A P2338 code can be caused by:

  • Incorrect air/fuel mixture
  • Damaged or defective knock sensor
  • Damaged or frayed wiring
  • Damaged or broken connectors

What are the Symptoms of the P2338 Code?

  • Warning or Check Engine Light may illuminate
  • Vehicle hesitates during acceleration
  • Decreased fuel efficiency
  • A loss in vehicle power or decreased acceleration
  • Spark knock

How Does a Mechanic Diagnose the P2338 Code?

  • Utilize an OBD-II scanner to check for a stored P2338 code
  • Visually inspect all wiring and connectors for damage
  • Check engine oil levels and oil quality
  • Listen to the engine for excessive noise
  • Check oil pressure
  • Test individual knock sensor
  • Clear the code, test drive the system, and rescan to see if the code appears

Common Mistakes when Diagnosing the P2338 Code

Because the knock sensor is essentially a microphone for the engine, it is possible that a sensor may be “hearing” an issue with a different cylinder and storing an inaccurate code. Ensure that all cylinders are checked for possible damages before returning to the road.

How Serious is the P2338 Code?

Since a vehicle’s knock sensors can decrease acceleration, this can impacting drivability and may possibly signify a more serious problem. This is considered a potentially serious code and it is recommended to have the vehicle immediately diagnosed and repaired.

What Repairs can Fix the P2338 Code?

  • Replace any damaged, frayed, shorted, or burned wiring or connectors
  • Change engine oil and ensure that it is full
  • Perform a manual engine oil pressure test
  • Replace affected sensor
  • Test electrical circuits (continuity and resistance)

Additional Comments for Consideration Regarding the P2338 Code

As not all knock sensors are easy to access, so test and diagnose all other sensors to avoid unnecessary engine removal or repair. Also, ensure that care is taken when removing knock sensors, as the coolant passage can cause severe burns.

Need help with a P2338 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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