jbtvt

Vibration and EMI would be even worse if moving than revving standing still. Road and powertrain vibrations and constant voltage fluctuations from pressing the brakes, using headlights,radio etc.

jbtvt

Didn't ask if it was a closed circuit, was only correcting a piece of terminology from page 1 that bothered me. I assume the knock sensor requires both power and ground wires which would make that portion of the system a closed circuit, regardless of the shielding wire.

It is possible for EMI to cause voltage drop. If it caused enough of a voltage drop due to defective shielding it seems to me a possibility that the reading could drop below what the ECU expects to see from any functioning knock sensor, thereby triggering a code 52.

rasdavid5446

Changed my distributor and haven't seen a check engine light since.

rasdavid5446

www.toyotanation.com/forum/80-89-95-toyota-pickup-hilux/309179-massive-truck-info-post-everyone-must-read-before-posting.html

h_louviere

But why would it do that when rpms are increased rapidly in neutral or anytime while driving but not when truck in neutral and rpms increased slowly?

jbtvt

Thread's going off the deep end again. To save future searchers the trouble, let me point out that nowhere on that page does it say anything about replacing a distributor to fix a code 52. 3 links on the page do deal with it - one says to do exactly what Schaeff has said throughout this thread, one has to do with what seals to order, the third...redirects you to this very thread. Secondly, no decent mechanic "tries" to fix an issue by throwing $200 parts at it, even if they were related to the issue. Again, I believe EMI could trigger a code 52 IF there was a faulty shielding wire, and a distributor being part of the electrical system may affect EMI readings. But the root cause of the issue would still be the shielding wire.

StealthySteph

i have the exact same problem the code 52 keeps reacureing my problem is check engine light comes on during acceleration already replaced ox sensor/egr valve/timming belt ks sensor with wire/pcv valve all to no good results.i noticed iside the wireing loom that the wires going to ks looks like it was installed after it arrived in california .looks like small coax cable.the problem remains as it was from the start rpm @2500 the light pops on every time without fail after reset of ecu.by the way i bought another ecu for test purposes same problem.it seems when the rpms get around 2500 the light comes on starting to think i have a bad ks paid $190.00 for it.i have owned this truck since 1990 new

twgin

Presently working through my own Code 52 experience. The code started appearing after a head gasket job by a local mechanic I have used for a long time. He called me up when he was into it and suggested a lot of work that should be done while it was torn down, good suggestions all. Unfortunately, after all done persistent Code 52. After some (not enough) research the problem was ASSumed to be that the pigtail was rotten and was disturbed during the HG job. A more experienced Toyota mechanic might have suggested putting in a new sensor and pigtail when the top end was torn apart. Anyway, going on the ASSumption that this was the case, another several hundred to go back in and replace the pigtail and the sensor, to absolutely no avail. Still Code 52's up the ying yang.

Trying to think through it I threw out the previous ASSumption and started thinking that maybe the sensor, et al, were GOOD and the engine really was knocking. Put a tank of premium in to no avail. Back to the boards for more research, specifically this great thread (thanks Schaeff !)

Code 52 doesn't mean the engine is knocking, it means no knock sensor signal to the ECU.

Most likely cause is bad wires, either the pigtail or the wiring back to the ECU. The sensor and the ECU fail rarely. Sometimes people sit backwards in the driver's seat or mash a few bananas into the valve covers and the code goes away, but this does not fix the wiring problem.

There is only one wire between the knock sensor and the ECU, there is not a power and a ground wire to the knock sensor (although the sensor body is grounded by virtue of being threaded into the engine block), there is only a single signal wire straight from the sensor to the ECU. This single signal wire is shielded against EMI; the shield begins in the pigtail, is connected through the pigtail/harness connector, and is connected to ground only at the ECU.

I spent part of the day running a replacement cable from the ECU to the pigtail. This link has some pictures of how a Supra guy fixed his, gives wire information. A little easier in the Supra as no pigtail involved.

http://oldschool.supracentral.com/htm/knock.htm

Finally, I think I have ID'ed the two pin male connector on the harness side that plugs into the pigtail: 90980-10242

I cut the plug off the harness and removed the pins; a new one is only $6-8, if I can get ahold of one fairly easily I'll use the new one instead of trying to rework to the old one.

Hopefully this will kill this Code 52 business, I'll post in a few days with results...

ChzSoda

So what's the good word on that rewire job, twgin? I've got my 3VZE apart in the driveway right now, elbow deep in a code 52 fix and a valve adjustment.

AZSPEED

Replacing the capacitor on the ks circuit in the ecu took care of mine. While I was there replaced all the capacitors. Remember that your ecu is 20 plus years old electronics wear out. If your ks is good and the wires are good it's the ecu.....pm me if you want i can fix it.

jbtvt

Lexus had issues with "quaternary ammonium salt" caps in their ~90's ECUs, so it makes sense that Toyota would too then although this the first I've heard of it. Maybe because Lexus wants $2k for their CPUs people are more inclined to try the DIY. Excellent info and clever fix!

http://www.clublexus.com/forums/ls40...capacitor.html

twgin

I still have my problem; have rewired it twice with progressively better coax to no avail. I'm thinking on how to proceed. I have the sheild grounded to the case of the ECU, or more accurately, to the little elbow bracket that holds the ECU in place, think I might try grounding shielding directly to a ground pin in one of the plugs. I'm intrigued by the post above about capacitors in the ECU, sounds logical. Still working it...

AZSPEED

It's very simply take your multimeter and check the wire at your ecu while the engine is running. You should see a small milivolt signal. If you do the wire to the KS and the KS are working. Code 52 is ecu not seeing signal. Now the problem is ecu. Why does everyone rewire with coax ground this and that? The capacitor on the KS circuit in the ECU is either out of spec or bad. If you look inside the ECU most parts are durable and should last a long time if not subjected to heat or water. The capacitors wear out with age. So the ECU does not get a good signal it can read so it throws code 52.lots of little stuff like this happens due to the age of the vehicles.

ChzSoda

That wouldn't be out of the question, given that mine is very unpredictably intermittent. Over 2 years I have not been able to find a pattern of temperatures, rain, driving style, fuel, etc etc that can consistently force the error. Sometimes it's there every startup for a month, then it might disappear for another month. Sometimes week intervals. Literally NO pattern. Maybe it's the ECU caps. I'm replacing the sensor and pigtail because I'm mid valve adjustment. If the code remains, I'll look into the ECU fix.

jbtvt

Verdict on that? I recently fixed a code 52 by swapping in a knock sensor with 260k miles on it and a new pigtail for $15. Pigtail was crispy and the likely culprit but figured I'd go with a known good sensor while I had it apart.

AZSpeed, I'm curious what caps you replaced, did you take any photos? I was in the ECU the other day and didn't see any electrolyic caps connected to the knock circuits, only ceramic which should outlast any of us alive. It's tough to trace the circuitry with the multi layered PCBs though.

RJR

Ceramic caps don't fail from age like electrolytics do, but it is certainly possible for them to crack due to vibration and thermal cycling. When that happens they either short or go open; either way they'll take the knock circuit out of operation.

YPO

FWIW...got OEM knock sensor with the blue band from dealer did not work. Got a Denso brand and problem solved. https://www.yotatech.com/forums/f116.../#post52294287

AZSPEED

When I hear that one knock sensor works and another doesn't that makes me think that the problem is more likely related to the ecu. Maybe one is generating more signal strength but if the ecu was working properly should be able to pick up both of them. That is just my thought.
I have another ecu laying around I will see if it is like mine and take some pics if it is to show what was replaced.mine is a 90 4.runner 5 speed I know the autos.have different plugs that year. Maybe the newer ones have different caps. I have a 94 lexus 1uz ecu I will see what it looks like.

a51young

In case anyone wants the part numbers for the wire harness side, I did some digging and here is what I found

A connector that fits (round rev) 90980-10242
It will need 2 terminals too, should be pn 82998-12080

The connector fits my old pigtail, but it is just the plastic connector housing, around $7, and the terminals are around $7 each from the dealer too.

My plan was to make a new harness from the pigtail to the ECU but since I didn't realize the connector didn't come with the terminals and non of the dealers have them in stock, I'm probably just going to use the old ones...

Hopefully that'll fix my code 52 as it's already got the new pigtail and this happened after a rebuild.

AZSPEED

A51young check to see if you have a signal at the ecu with the engine running. If you have a signal.check your capacitor on the KS circuit. Where are you in AZ? I'm in Tucson