What does it mean?
This diagnostic trouble code (DTC) is a generic powertrain code, meaning it applies to OBD-II equipped vehicles (Dodge, Ram, Ford, GMC, Chevrolet, VW, Toyota, etc.). Although generic, the specific repair steps may vary by make/model.
In instances where I have been faced with diagnosing a stored P033E code, it has been indicative of the powertrain control module (PCM) detecting an intermittent knock sensor signal for engine bank two. The knock sensor 4 designation may refer to a particular sensor (in a multi-sensor setup) or it may point to a specific cylinder. Bank 2 refers to the engine bank that does not contain cylinder number one. Consult a reliable vehicle information source for the knock sensor system configuration for the vehicle in question.
Typically threaded directly into the engine block, the knock sensor is a piezoelectric sensor. The location of sensors in a multi-sensor system can vary by manufacturer, but most are located on the sides of the block (between the cylinder head coolant jacket freeze plugs). Knock sensors that are located on the sides of the engine block are often screwed directly into engine coolant passages. When the engine is hot and the engine cooling system is under pressure, removing these sensors can result in severe hot coolant burns. Before removing any knock sensor, allow the engine to cool and always dispose of coolant properly.
A piezoelectric sensing crystal is at the heart of the knock sensor. When shaken or vibrated, the piezoelectric crystal produces a small amount of voltage. Since the knock sensor control circuit is normally a one-wire ground circuit, the voltage generated by vibration is recognized by the PCM as engine noise or vibration. The severity of the vibration encountered by the piezoelectric crystal (inside the knock sensor) determines the level of voltage produced in the circuit.
If the PCM detects a degree of knock sensor voltage indicating spark knock; it may retard ignition timing and no knock sensor control code may be recorded. If the PCM detects a level of knock sensor voltage that indicates more severe engine noise (like a connecting rod contacting the inside of the engine block), it may interrupt fuel delivery and ignition spark to the affected cylinder and a knock sensor code will be stored.
A very small voltage is always produced by the knock sensor when the engine is running. This is because slight vibration is unavoidable, no matter how smoothly the engine is running. If the PCM detects an unexpected signal from knock sensor 4, such as battery voltage, complete battery ground, or pulsing voltage, a P033E code will be stored and a MIL may be illuminated.
Related knock sensor/circuit malfunction codes include P0324, P0325, P0326, P0327, P0328, P0329, P0330, P0331, P0332, P0333, and P0334.
Code Severity and Symptoms
A stored P033E code could be indicative of a severe internal engine failure. For this cause, it should be addressed with some urgency.
Symptoms of this code may include:
Decreased engine performance
Hesitation upon acceleration
Loud noises from the engine area
Decreased fuel efficiency
Causes
Possible causes for setting this code are as follows:
Faulty knock sensor
Internal engine malfunction
Misfire/s
Contaminated or poor quality fuel
Faulty knock sensor control wiring and/or connectors
Incorrect PCM or PCM programming error
Diagnostic and Repair Procedures
To diagnose a P033E code, a diagnostic scanner, digital volt/ohmmeter, and a reliable vehicle information source will be needed. If the engine feels like it is knocking or is excessively noisy, resolve this issue before attempting diagnosis for any knock sensor code.
Consult your vehicle information source for technical service bulletins (TSBs) that coincide with the symptom(s) displayed and the code(s) stored in the vehicle in question. If the issue you are experiencing is common; the correct TSB can help lead to a successful diagnosis. Follow the diagnostic steps in the TSB and you will likely arrive at the correct solution.
I like to start with a visual inspection of all wiring harnesses and connectors related to the system. I look for burned, corroded, or otherwise broken wires and connectors that may create an open or shorted circuit. Knock sensors are often located in the lower portion of the engine block. This makes them susceptible to damage when heavy components (like starters and motor mounts) are replaced. System connectors, wiring, and fragile knock sensors are frequently broken during nearby repairs.
Connect the scanner to the vehicle diagnostic connector and retrieve all stored codes and freeze frame data. Note this information for use in the diagnostic process. Clear the codes and test drive the vehicle to see if they reset.
If the P033E resets, start the engine and use the scanner to observe live knock sensor data. If the scanner indicates that the knock sensor voltage is not within manufacturer specifications, use the DVOM to test the live data at the knock sensor connector. If the signal at the connector is within specifications, suspect a wiring problem between the sensor and the PCM. If the voltage at the knock sensor connector is not within specifications, suspect a faulty knock sensor.
Additional Diagnostic Notes:
Multi-knock sensor systems are arranged differently from vehicle to vehicle. Be careful to address the correct knock sensor for the displayed code
Beware of hot, pressurized coolant when removing knock sensors that are threaded into engine coolant passages