Technical Description of OBD-II Trouble Code
The knock threshold in Cylinder 3 has been exceeded.
What is the meaning of P2338?
P2338 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 of the vehicle.
If your vehicle has stored a code P2338 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 #3 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 three, it will store a code P2338 and illuminate the MIL. Multiple failure cycles may be required for the MIL to illuminate.
What is the severity of this DTC?
When a P2338 code is stored, it is important to diagnose the cause as soon as possible. The severity of symptoms associated with this code can range from minimal to catastrophic.
What are some of the symptoms of the code?
Symptoms of a P2338 trouble code may include:
What are some of the common causes of the code?
Common causes of this code may include:
What are some P2338 troubleshooting steps?
Ensure that the engine has the correct oil level and is in good working order. Eliminate any actual engine noise, such as spark knock, before diagnosing a P2338 code.
To accurately diagnose a P2338 code, 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 exhibited.
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. 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, the code may be more difficult to diagnose because it is intermittent. The condition that caused the P2338 code to be stored may need to worsen before an accurate diagnosis can be made. If the code is restored, continue with the diagnosis.
Use your source of vehicle information to obtain connector face views, connector pinout charts, component locator charts, wiring diagrams, and diagnostic flow charts specific to the code and vehicle in question.
Perform a visual inspection of the related wiring and connectors. Repair or replace any wiring that is cut, burned, or damaged. Consider replacing spark plug wires and boots if the vehicle is beyond the recommended maintenance interval for a tune-up.
Before removing the knock sensor, disconnect the PCM and use the DVOM to check continuity in the knock sensor circuit. Take caution to avoid getting burned by coolant or oil when removing the sensor. Test continuity through the sensor and back to the PCM connector.
