OK, I have a 1989 22re. I am getting a Code 52, knock sensor code, but only if the motor is not warmed up. If I start it and let it come to temp, it will not throw the code. Also, if it does throw the code and I drive it and again, once it is up to temp, I shut down and restart... no code.

My question is, when I am throwing a 52 code, is that telling me the knock sensor is sensing a knock, or is it telling me the knock sensor is bad?

I searched and was not able to find an answer to these questions. Thaks

 

I just had this same issue with my 89 4Runner but mine has a 3.slow - with only throwing a code if I put a load on it without letting it come up to op temp first. Then after a week or so, the code came on only after it got to op temp.
The guy I take my 4Runner to is a Toyota Master Mechanic and he said (at least in my case) that the throws the code either when there is a knock or when the computer stops receiving a signal from the sensor. In my case, the problem was that the wire harness to the knock sensor had dry rotted and the wires oxidized and were cracking. At 25 years old and 210k miles, we decided to replace the harness as well as the sensor. Plus, while we had it apart, we ended up replacing most of the hoses, valve cover gaskets, cleaned up the entire motor. I have had my 4Runner for close to 10 years and it has never driven better than it does now

Not sure if that really answers your question but that was my experience.

 

Its when the ECU is not sensing the knock sensor, So its ether the wire is bad (most likely) or the sensor itself has become faulty.
The ECU is always seeing a signal from the sensor, It only makes an adjustment (retards timing) when it becomes to extreme.

 

Thank You, thats exactly whet I needed.