Technical Description of OBD-II Trouble Code
The knock threshold in Cylinder 4 has been exceeded.
What is the meaning of P2339?
P2339 is a generic powertrain code that applies to many OBD-II vehicles (1996-newer), including Mercedes-Benz, Ford, Sprinter, Nissan, and others. The exact repair steps may vary depending on the year, make, model, and powertrain configuration.
If your vehicle has stored a code P2339 and the malfunction indicator lamp (MIL) is illuminated, it means that the powertrain control module (PCM) has detected a signal from the knock sensor in cylinder #4 that is outside of the acceptable threshold.
The knock sensor is responsible for monitoring excessive vibration and noise in an individual cylinder or bank of cylinders. It uses a chemical reaction to detect engine knock, which can be caused by timing, detonation, or internal engine failure. The knock sensor reacts to changes in engine noise by increasing voltage. Since it is part of a low voltage circuit, any changes in voltage are easily detected by the PCM.
If the PCM detects an unexpected level of voltage on the knock sensor circuit for cylinder four, it will store a code P2339 and illuminate the MIL. Multiple failure cycles may be required for the MIL to illuminate.
What is the severity of this DTC?
When a P2339 code is stored, it is important to diagnose the cause as soon as possible. The symptoms associated with this code can range from minimal to catastrophic.
What are some of the symptoms of the code?
Symptoms of a P2339 trouble code may include:
What are some of the common causes of the code?
Common causes for this code may include:
What are some P2339 troubleshooting steps?
Ensure that the engine has the correct oil level and is in good working order. Any actual engine noise, such as spark knock, must be addressed before diagnosing a P2339 code.
To accurately diagnose a code P2339, you will need a diagnostic scanner, a digital volt/ohmmeter (DVOM), and reliable vehicle information.
It may be helpful to search for technical service bulletins (TSB) that match the stored code, vehicle information, and symptoms. This information can be found in your vehicle information source and may provide a quick solution to the diagnosis.
After connecting the scanner to the vehicle diagnostic port and retrieving all stored codes and freeze frame data, write down the information in case the code is intermittent. Then, clear the codes and test drive the vehicle until either the code is restored or the PCM enters readiness mode.
If the PCM enters readiness mode, diagnosing the code may be more difficult because it is intermittent. The condition that caused the P2339 code to be stored may need to worsen before an accurate diagnosis can be made. If the code is restored, continue with the diagnosis.
You can obtain connector face views, connector pinout charts, component locator charts, wiring diagrams, and diagnostic flow charts specific to the code and vehicle in question from your vehicle information source.
Inspect the related wiring and connectors visually. Repair or replace any wiring that is cut, burned, or damaged. Spark plug wires and boots should be replaced as part of scheduled maintenance. If the vehicle is overdue for a tune-up, suspect bad spark plug wires/boots as the cause of a stored P2339 code.
After disconnecting the PCM, use the DVOM to check continuity in the knock sensor circuit. Take caution when removing the knock sensor to avoid contact with coolant or oil. Test continuity through the sensor and back to the PCM connector.
