Seeking Tech Help: I have a 1996 Toyota Camry V6. About a year ago, the check engine light came on and the car was riding rough. Turned out to be a knock sensor, and both were replaced at that time. The car started running better immediately, but the check engine light came back on within a week, indicating a knock sensor problem again. Mechanic got new sensors, and replaced both again. Within a couple weeks the check engine light came back on, and surprise, surprise... it was a knock sensor code. We ignored it for 6 months and the car has been riding beautifully with great gas mileage. As my emissions test is approaching, I have to clear this up, so my mechanic has replaced multiple wiring harnesses and the ECU. Resets the check engine light, and within blocks it comes back on, showing a knock sensor code. Car is riding like a dream. Any help on how I can fix this and pass emissions (Illinois). Thank you!

 

The sensor outputs a constant 7.1kHz signal. A code is set when the ECU fails to receive this knock sensor signal with engine operating between 2K and 5.6K rpm.

Toyota dealers check the signal output visually with their diagnostic tool You could use a scanner with this capability or an oscilloscope. Operate engine between say 2K and 4K to get a decent signal amplitude. Check for a constant signal and decent output amplitude. Output amplitude should vary with engine RPM.

Check sensor ground points for continuity.

Some state the type of sensor brand makes a difference such as Denso or Toyota brand.

 

This was very detailed info and you responded so quickly! Thank you. Sharing this with my mechanic now!

 

Post back with your progress.