Cel Goes On And Off -- Knock Sensor 55

[John Martin]

I know that this is the Bank 1 (Rear) knock sensor code. What I can't figure out is why it only comes on after I heat the car up significantly by driving it on the highway. Does it sound like a failed sensor or something wiring related?

I just put the intake plenum (not the actual manifold) back on as part of my repair of the valve cover gaskets, and I don't want to have to mess with this if I don't have to.

I do have some knock at idle, and probably higher speeds, on what sounds like a single cylinder. It was not so pronounced before I fixed the valve covers and performed a tuneup -- plugs, wires, rotor, cap. Here are the possible knock causes I can think of:

Valves need adjusting -- I'm hoping that this is not it

I put in 20-50 oil while I was tracking down leaks, and have yet to change back to 30 weight

I changed the plug wires to aftermarket (don't know whether the ones I replaced were OEM)

I have not Seafoamed the car yet, so there's lots of carbon

I'll check the timing again, but it doesn't sound like a general timing problem

Any other possible causes I might have missed?

Thanks,

JM

[Toysrme]

Get rid of the carbon & clean the EGR valve. You may have a cylinder lean also.

The valvetrain is kinda far out there.

But yeah, check the timing too, and the o2 sensors.

Thats for fixing the knocking.

Understand that the code isn't thrown for knocking. It's thrown when the sensor has a short in the loop. Either the wiring, or the sensor is bad. That means pulling the upper manifold off, along with the lower.

[John Martin]

Understand that the code isn't thrown for knocking. It's thrown when the sensor has a short in the loop. Either the wiring, or the sensor is bad. That means pulling the upper manifold off, along with the lower.

So what's the best way to check the sensor, and, if it's bad, is a used one an option? The new ones seem to be in the $150 range which is more than I want to spend on this problem. The risk with a used one is that I'd have to remove the intake twice, which I'd like to avoid. Do the knock sensors go bad, or is it usually the wiring?

Thanks,

JM

[LarryR]

MY experience was the wiring was bad. So I replaced it and still had the code. I bought a used one and when I went to put it in I noticed that the sensor wasn't very tight. I still put the used one in because like you I didn't want to do the job 3 times. I really believe that it was probably good. It did omh out ok. You can be sure that the wires will be pretty burnt because of where they are located.

Hope this helps.

Larry :D

[John Martin]

Thanks, Larry. That is exactly the kind of experience I am trying to tap into.

This part of the Toyota design does not inspire confidence in the wiring, sensor or connector, as having unshielded electricals underneath the intake manifold would seem to me a generally bad idea. But then I am prejudiced, since my automotive experience is mostly with pre-pollution-control vehicles. Their wiring was mostly worn as an exoskeleton, rather than a lymphatic system.

I'll report back once I have resolved the problem.

JM