So I just got my first 4Runner and found it has probably most of the
issues mentioned on this board, the most frustrating being the power robbing
code 52.
I Ohmed the knock sensor wires from ECU to sensor and they look good, put a scope on it and see a small AC signal with a lot of spikes(ignition noise I am guessing).
I went to the junkyard and got a sensor and pigtail from a 94 and it appears to test good using the Oscope.
So I cut the wire from the ECU connector near the ECU, and hooked up the new used sensor and pigtail. I wrapped the sensor in foil and grounded it to the chassis.
Started the engine let it run a few minutes observing the Oscope, revved to to about 3000 a couple times, no code 52, so I drove it. Got a hundred yards or so and the CE light came on, code 52 again.
Again I see noise spikes on the Oscope, which I assume is what is triggering the code.
My guess is engine noise is entering the wiring harness and effecting the ECU, inducing errors into the KS circuit. Does that sound plausible?
While looking under the hood at the wiring harness I see many cracks in the harness insulation and can easily cause more by simply moving the harness.
My thought is to replace the ECU harness, but I don't want one from Ebay as I may get crap
and induce other issues.
Finally, my question is : Are new harnesses available or will I have to build my own?

 

Look online or go to your local dealer .

You might get lucky.