My car was throwing code 0304 from the ECU, (Knock sensor) so I decided to remove the sensor, cleaned the sensor with special electronics spray (from pepboys), as well as the 2 grounds at the upper intake manifold that are part of the knock sensor wiring, cleared the codes on the ECU, take the car for a drive (2 hours), AC on, AC off, and now the ECU doesn't throw the 0304 code anymore, just the happy 0505 ! Hope this can help others ! By the way, I did not need to remove the upper and lower intake manifold to remove the knock sensor as the HAYNES MANUAL stated, just get my hands a little scared, but that's all !