some drunk guy

After Reading almost every thread on this board about code 52, knock sensor signal, Im more frustrated than ever, and Im looking for some ideas.

Here's what I have. 1991 toyota 4runner. 3.0 I did an engine swap and I swapped the sensor from the old block to the new one, I bought a new Knock Sensor wire plug from toyota dealership and snapped in on because the old was brittle and frayed. Put the whole engine together, everything went smooth, fired it up. No Check Engine Light....Untill, I started driving. Read the code...52

So I bought a new knock sensor, and another new knock sensor wire, and I drilled and tapped the rear engine hanger, like Ive read people can do, to "by pass" or "test" the Knock Sensor signal. Still... CEL Code 52

I pulled the conector plug, on the harness side under the throttle body, and found the pin for it on the ECU and I power probed a signal through, and the wire harness is good signal at the ECU

So whats next to trouble shoot?

I have read that the knock sensor wire is a coax wire with a grouned shield on it, and some may need to be "additionally" grounded at both ends of the wire ???

Can anybody confirm this? Anyone have any other ways to trouble shoot this frustration of a code!!

Thanks in advance, for any info..

doublel

Can't offer any help but I can sympathize with you. I have a thread on here about the dreaded code 52 as well. I haven't torn mine down yet but have tried mounting an external KS and I still have the code. I made up a new shielded wire and ran it direct from my external KS straight to the ECU. I grounded the ECU side (don't ground both ends), fired it up and took it for a drive and get the CEL as soon as I accelerate. I was attempting to "test" with the external KS before I went through all that you have in tearing into your engine to replace the KS and pigtail and still have the problem.

Did you replace the KS with a Toyota OEM KS? There have been a couple of instances on here where I read that some had issues with non OEM knock sensors. Other than that I've got nothing.

some drunk guy

Yes, replaced with Toyota oem Knock Sensor. So how do you "additionally" ground the wire at the ECU? Got any Pics?

TNRabbit

Could also be a problem in the wiring harness....between the pigtail & ECU.

doublel

I crimped on a ring on the shield wire and grounded it to one of the bolts that holds the ECU. Don't have any pictures of it.

I have gleaned from other posts on here that in addition to having continuity from the KS connector to the ECU that you need to be sure there is no continuity from the KS connector (the single wire that goes to the KS) to ground.

some drunk guy

Im a little confused but curious about this last statement. Can you explain a little more detail please.?

some drunk guy

If Im reading that right, at the Knock Sensor connector (the part that snaps onto the knock sensor), that should be reading a positive signal to the ECM correct? and not a ground signal?

doublel

What I understood from reading those posts were that you should have continuity from the KS connector (yes, the part that snaps onto the KS) to the ECU. You should also check the KS connector (again from the part that snaps onto the KS) to ground and make sure that there is no continuity there.
The way I understood the posts were that if you have an open circuit on the KS wire OR if the KS wire has continuity to ground it will set the "52" code.

some drunk guy

Ok thanks doublel Ill report back.

some drunk guy

Well so far no luck, I read in the FSM that there is only 3 main causes of Code 52.
1) The Knock Sensor: but from what Ive been reading, the sensor itself, rarely goes out, most of the time its a wire issue.
2)Wiring or circut:

3)ECU

Im going to try to re run a coax wire to the ECU, where can I buy coax wire?? How hard is it to splice a good connection with the shield on it??

jtree3vze

I just had a similar problem with my 91 3vze. Replaced knock sensor, pigtail, and then all wiring back to ecu. I used the original wire from the wiring harness to connect my new shielded wire to the ecu.

I was still getting error code 52. I then de-pinned the knock sensor wire from the ecu plug/connector and checked to see if the wire was landing on the pin inside the ecu body. Sure enough, the wire connection was loose/not great on the ecu pin.

I went to a salvage yard and found a donor vehicle and got a “new” used ecu plug with all the wires attached. Chopped the plug with about 4” of wire sticking out if it. I then de-pinned the knock sensor wire from the plug and replaced my bad knock sensor wire end with the new wire end (soldered it on), shoved the new wire end into the ecu plug and put the plug back into the ecu. Fired up the engine and the code 52 was gone finally!

moral of the story - de-pin the knock sensor wire from your plug connector and check to see if the wire is making a good connection to the ecu pin. De-pinning requires a special tool available at Napa and a special skill I learned from watching a few YouTube videos on how to de-pin a Toyota ecu plug. But this was the only connection I hadn’t replaced, and it was the fix for my knock sensor code 52.