Technical Description of OBD-II Trouble Code
Intermittent Circuit Issue with Knock Sensor 4 (Bank 2)
What does that signify?
This diagnostic trouble code (DTC) is a generic powertrain code that is applicable to OBD-II equipped vehicles (such as Dodge, Ram, Ford, GMC, Chevrolet, VW, Toyota, etc.). While it is a generic code, the specific repair steps may vary depending on the make and model of the vehicle.
Whenever I have encountered the diagnosis of a stored code P033E, it has indicated that the powertrain control module (PCM) has detected an intermittent signal from the knock sensor for engine bank two. The designation of knock sensor 4 can refer to a specific sensor in a multiple sensor configuration or it can indicate a particular cylinder. Bank 2 refers to the engine bank that does not contain the number one cylinder. To determine the configuration of the knock sensor system for the specific vehicle in question, consult a reliable source of vehicle information.
The knock sensor is typically threaded directly into the engine block and it is a piezoelectric sensor. The location of the sensors in a multi-sensor system may vary among manufacturers, but most are located on the sides of the block, between water jacket freeze plugs. Knock sensors that are positioned on the sides of the engine block are often threaded directly into engine coolant passages. It is important to note that removing these sensors when the engine is warm and the engine cooling system is pressurized can result in severe burns from hot coolant. Therefore, before removing any knock sensor/s, allow the engine to cool down and always dispose of coolant properly.
The knock sensor contains a piezoelectric sensing crystal, which is the core component of the sensor. When the crystal is shaken or vibrated, it generates a small amount of voltage. Since the knock sensor control circuit is typically a one-wire ground circuit, the PCM recognizes the voltage generated by the vibration as engine noise or vibration. The level of voltage produced in the circuit depends on the severity of the vibration experienced by the piezoelectric crystal inside the knock sensor.
If the PCM detects a level of knock sensor voltage that indicates spark detonation, it may retard ignition timing and no knock sensor control code will be stored. However, if the PCM detects a higher level of knock sensor voltage that suggests a more severe engine noise (such as a connecting rod contacting the inside of the engine block), it may cease fuel delivery and ignition spark to the affected cylinder, and a knock sensor code will be stored.
A small amount of voltage is always generated by the knock sensor when the engine is running. This is because a slight amount of vibration is inevitable, regardless of how smoothly the engine runs. If the PCM detects an unexpected signal from knock sensor 4, such as battery voltage, complete battery ground, or pulsing voltage, a code P033E will be stored and the malfunction indicator lamp (MIL) may illuminate.
Other knock sensor/circuit trouble codes that are related to this issue include P0324, P0325, P0326, P0327, P0328, P0329, P0330, P0331, P0332, P0333, and P0334.
Severity of the Code & Symptoms
A stored code P033E could indicate a severe internal engine failure. Therefore, it should be addressed with a certain level of urgency.
The symptoms associated with this code may include:
Possible Causes
The potential causes for this code to be set are:
Diagnostic and Repair Procedures
To diagnose a code P033E, you will need a diagnostic scanner, a digital volt/ohmmeter, and a reliable source of vehicle information. If the engine sounds like it is knocking or excessively noisy, address that issue before attempting to diagnose any knock sensor codes.
Refer to your vehicle information source for any technical service bulletins (TSB) that correspond to the exhibited symptoms and stored codes in the specific vehicle. If the problem you are experiencing is a common one, the appropriate TSB may assist in achieving a successful diagnosis. Follow the diagnostic steps outlined in the TSB, and you will likely arrive at the correct solution.
I prefer to begin with a visual inspection of all wiring harnesses and connectors related to the system. I am looking for any burnt, corroded, or broken wiring and connectors that may cause an open or shorted circuit. Knock sensors are often located in the lower part of the engine block, which makes them vulnerable to damage during the replacement of heavy parts like starters and engine mounts. System connectors, wiring, and delicate knock sensors are frequently broken during repairs in the vicinity.
Connect the scanner to the vehicle’s diagnostic connector and retrieve all stored codes and freeze frame data. Take note of this information for use in the diagnostic process. Clear the codes and test drive the vehicle to see if any codes are reset.
If the P033E code is reset, start the engine and use the scanner to monitor knock sensor data. If the scanner indicates that the knock sensor voltage is not within the manufacturer’s specifications, use the DVOM to test live data at the knock sensor connector. If the signal at the connector falls within the specifications, suspect a wiring issue between the sensor and the PCM. If the voltage at the knock sensor connector is not within the specifications, suspect a defective knock sensor.
Additional diagnostic notes:
