What does it mean?
This diagnostic trouble code (DTC) is a generic powertrain code, meaning it applies to vehicles equipped with OBD-II. Although generic, specific repair steps may vary by make/model.
Knock sensors are used to detect engine pre-detonation (engine knock or pinging).
The knock sensor (KS) is typically a two-wire sensor. A 5-volt reference is provided to the sensor, and there is a signal return from the knock sensor to the PCM (Powertrain Control Module). The sensor’s signal wire informs the PCM when a knock occurs and its severity. The PCM will retard spark timing to prevent pre-detonation. Most PCMs have the capability to learn spark knock trends in the engine during normal operation.
A P0333 code is a generic DTC, so it applies to all vehicle makes and refers to a high output voltage from the knock sensor. In many cases, this means the voltage is above 4.5V, but this specific value depends on the particular vehicle make and model. This code refers to the sensor on bank #2 (the engine side that does not contain cylinder #1).
Symptoms of a P0333 DTC may include:
- MIL (Malfunction Indicator Lamp) illumination
- Audible knocks from the engine compartment
- Engine pinging under acceleration
- Loss of power
- Irregular RPM
Potential causes of a P0333 code include:
- Damaged knock sensor connector
- Open or short-to-ground knock sensor circuit
- Short-to-voltage knock sensor circuit
- Failed knock sensor
- Loose knock sensor
- Electrical interference in the circuit
- Low fuel pressure
- Incorrect fuel octane
- Mechanical engine problem
- Faulty/defective PCM
Possible Solutions
If you hear the engine knocking (detonation), first repair the source of the mechanical issue and retest. Ensure the correct octane fuel has been used (some engines require premium fuel, consult the owner’s manual). Beyond that, for this code, the problem will likely lie either with the knock sensor itself or with the wiring and connectors running from the sensor to the PCM.
Realistically, for a DIY vehicle owner, the best next steps are to measure the resistance between the two terminals of the knock sensor wire where they enter the PCM. Also check the voltage at the same terminals. Compare these figures to the manufacturer’s specifications. Also inspect all wiring and connectors leading from the knock sensor to the PCM. Additionally, you should also check the resistance of the knock sensor itself using a digital voltmeter (DVOM), comparing it to the vehicle manufacturer’s specifications. If the knock sensor’s resistance value is out of specifications, it must be replaced.
Other knock sensor DTCs include P0324, P0325, P0326, P0327, P0329, P0330, P0331, P0332, P0333, P0334