P0333

Diagnostic Chart:

Schematic:

The knock sensor 2 (bank 2) is a piezoelectric device that produces an AC voltage of different amplitude and frequency depending on the level of engine mechanical vibration. The ECM uses the sensor to determine if spark knock is occurring during a cylinder combustion event. If spark knock is detected, the ECM will retard timing on succeeding firing cylinders until the spark knock is eliminated. The ECM will always try to work back to zero compensation or no spark retard. In order to differentiate between normal engine noise and actual spark knock, the ECM will sample the knock sensor 2 signal for a certain length of time under different engine speeds and loads during non-cylinder firing events. This sampling is used to determine a range of acceptable normal engine noise. DTC P0333 sets when the ECM detects too much normal engine noise from knock sensor 2 for a certain length of time.

DTC PARAMETERS
DTC P0333 will set when if knock sensor 2 signal voltage exceeds the maximum normal engine noise level (based on engine speed and load) when:
^ Engine speed is greater than 2400 rpm
^ ECT is greater than 40°C (104°F)

DTC P0333 diagnostic runs continuously once the above conditions have been met.

P0333 is a type B DTC.

DIAGNOSTIC AIDS
Knock sensor 1 and knock sensor 2 voltages should be around 0.25 volts at idle and up to around 2 volts at fuel cutoff in Park. If a short voltage occurs on either wire, KNOCK SENSOR voltage on Scan tool will be slightly higher at idle, but may look normal as the engine is revved.

With the engine Off, the voltages on the Scan tool for each sensor should be the same. If they are, DTC P0333 is most likely due to excessive engine noise and not a short to voltage.

DTC P0333 may set due to excessive noise due to mechanical concerns. Possible causes may include:
^ Valve lifter noise
^ Belt tensioner loose
^ Loose accessory bracket
^ Noisy A/C compressor operation
^ Low octane fuel in high ambient temperatures under heavy engine load

The ECM has the ability to learn spark retard. If spark knock is present long enough, the ECM may retard timing far enough to incur a noticeable reduced engine power condition. Spark timing will return to normal once the spark knock condition is corrected.