DrCreosote

1990 4Runner, 3VZE, Automatic

Just started throwing code 52. The engine was rebuilt some time ago, but it took me a loooooong time to get it installed due to health issues, and even longer to get it road worthy. It's been running great, but CEL came on two days ago; code 52. The rebuilder replaced the knock sensor and the pigtail. I have about 15000 miles on the rebuild, so it isn't like it's brand new, but not terribly old. I sent them an e-mail to ask if they used Toyota branded knock sensor and was told they have no idea what brand they put in it. Visual inspection of the wiring harness shows the wrap flaking off. In my mind, the easy thing is to test the signal wire to the ECU. After scouring this site and the web for a day or so, I find references to simply replacing it, but no details on what wire or class of wire to use. Some say TV coax, like an RG6, I presume. All of this I can do, but I'm hoping for more clarification before I go to that much trouble. As for testing the wire, testing for a short is easy enough, but should I also be testing for resistance? Of course I should, but how much resistance should it have?

I've found lots of posts that refer to forums that detail the full project of replacing the wire, but no one gives a link to them, they just say "they are out there" and I'm apparently using the wrong search terms to get there. If anyone can link me to a post that's already done that replacement and gives details, I would certainly appreciate it.

Thank you in advance.

DrCreosote

So while I was at work today, I managed to find some time to study on this and I found a few things:
For testing the wiring from the ECM side, To test, best to do at ECM connector so you can test wiring in between as well:

Automatic: test resistance between term-13 and ground
Manual: test resistance between term-14 and ground

Should be greater than 1M-ohm (> 1000K ohm). But not fully open or shorted. If fully open or shorted, then it might be wiring. Re-test at sensor itself.

And I also found a YouTube video that describes a way to test the knock sensor itself:


If anyone else is dealing with this problem, perhaps it will help.

DrCreosote

Just in case anyone is watching this post or interested in any way at all. I tried following the steps I listed above and I can tell you, it isn't gonna work. The ECM has a LOT of wires going into it. There are three plugs and none of them are numbered, so there is not going to be any number 12 or number 13 to easily locate.

However, I was not to be beaten that easily and I set about testing from the other end, where I should have started. One lead had a nice ground, the other didn't. I didn't really know which one was supposed to be grounded, but I knew one and only one would be. Resolved that the problem is not in the wires, I put it all back together and went to look up prices on a new one and plan a weekend repair.

However, when I got in the car to come to work today, no CEL. It made it all the way with no problems (about 28 miles) so I feel pretty good that it just needed to be unplugged and re-connected. That's one of those repairs they always tell you to do, but almost never works. I'm happy to say it did work this time. I'm still gonna get new parts though because I don't know if the wire and sensor are Toyota branded or not. Since the rebuilder can't say for sure, I'm going to presume there is a fix in my future.

So the lesson here is to check and clean your connections as an early step in your diagnostic procedure.

cmorla23

Tengo el mismo problema, soy de Venezuela