doublel

I've searched and think I have read every thread on the site. 92 4Runner, 3vze, auto 4wd. I bought it in January...no CEL and no codes set. Shortly after I bought It, I replaced the timing belt, water pump, thermostat, drive belts, spark plugs....just general preventative maintenance. Also tested and ended up replacing the TPS and cleaned the throttle body while I had it removed for the TPS replacement.

About two months after I had completed the repairs I get my first check engine light and it is the dreaded "52". At first it was itermittent but then it pretty much became a solid fault. After reading everything that I could find on the site, I checked the continuity on my wiring and all checked out ok. I also checked to make sure that there was no continuity between the sensor wire and ground and there was not.

I decided to order a knock sensor which I ended up buying off of Ebay as it appears others have done on here and after reading that it is usually a wiring issue and not the knock sensor or ECU. It is a genuine OEM knock sensor. I ordered a new pig tail from a Toyota dealer. Upon inspection, there was some missing insulation on my wiring harness near the knock sensor plug even though everything checked out, so I made up a new knock sensor wire using a piece of shielded coax and ran it direct to the ECU. I made a bracket and mounted the knock sensor externally and hooked up the new wire. As soon as I start accelerating and get around 1500-1800 rpm I get the CEL. I contacted the Ebay seller that I bought the knock sensor from and he agreed to send me another knock sensor. I replaced it and still get the CEL everytime I accelerate. I rechecked the continuity on my new direct wire and all is good. I have checked and cleaned up the engine grounds.
I decided to hook my new direct wire back up to my existing knock sensor pig tail and I am back to an intermittent CEL. I can accelerate and drive until I have to stop for the first time. Upon acceleration from that first stop I get the CEL. I can pull over and turn off the engine and restart and no CEL. Again I can drive until I have to stop and upon acceleration from that stop I get the CEL. I am just about at wits end with this thing. Is there anyway to check the ECU or do I just have to buy a used one and hope that it is good and that it will fix the problem?

I am sure glad that I didn't tear into the engine and replace the knock sensor and pigtail at this point or I would be really upset. Tell me what I have missed and more importantly what else I can do to get rid of this code!

abecedarian

Make sure one end of the shield is grounded, usually by the ECU is best. It helps keep electrical noise off the KS wire itself for a good signal to the ECU. Without the ground, the signal will have interference from the ignition and injection wiring.

scope103

You forgot to replace the knock sensor and the pigtail.

Actually, your knock sensor is probably fine, and the pigtail is probably bad. The knock sensor is just as tough as that (old) pigtail is brittle and broken.

You said you mounted a replacement knock sensor "externally." Do you have any reason to think that would work?

I have no way to guarantee that your old knock sensor is good, so if you're really worried about wasting your time go ahead and replace it. But your pigtail is almost certainly bad. So suck it up and pull off the lower intake manifold. You'll be glad you did.

doublel

I only grounded the cable that I made up at the ECU. It is not grounded on the knock sensor end.

I didn't forget to replace the KS and pigtail, I was trying to determine if the existing knock sensor and pigtail was the culprit BEFORE I went thru all the work required to replace it. I have read on this forum where others have done the same. I have also read where some have replaced them both and still get the code 52.

If it is usually a wiring problem then why is my temporary mounting of the knock sensor externally not working.....at least fooling the ECU where it "sees" the knock sensor? No way am I willing to tear down and replace the knock sensor and pigtail until I know it is definitely the problem. One thing I failed to mention is that the previous owner had the knock sensor and pigtail replaced several years ago by a Toyota dealer so the pigtail is not the stock wire. Granted it could still be bad but may not be as brittle as a stock wire would be.

scope103

The knock sensor is a piezo transducer that produces a voltage pulse when it is subject to a shock with the correct frequency spectrum. So if the knock sensor is, for instance, being held in your hand it will not produce the voltage pulse for the ECU to see. For the knock sensor to produce any output (and make the ECU think it is getting a signal), your temporary mounting would have to be mechanically coupled to pick up the correct vibration.

I have no idea where that would be, other than right between the heads where it is supposed to be installed. I have read some threads where others have tried bolting one to a lifting eye, but I don't believe any of those actually worked.

While your efforts to assure electrical continuity between the ecu and the pigtail are wise, I believe the "most likely" culprit is the pigtail, based my observations and the experience of many others. But there is no guarantee that is actually your problem.

Is there some way to tell for sure? Some on this list have talked about putting a digital storage scope on a working knock sensor and recording what a "good" waveform would look like. Then you could hook your oscilloscope up to your wiring and check. But I don't know of anyone who has actually done that.

AZSPEED

I also changed everything and nothing helped i adj the timing to run better when the KS retards it. I got tired after trying everything but an ecu. New sensor new pigtail ran coax moved KS nothing helped, now there is a Lexus V8 in my garage waiting to be transplanted into my runner. Good Luck keep us posted.

doublel

Getting way over my head here! :-)

I read a few threads where some had relocated the KS to the lift hook and some had made a bracket and relocated it and it eliminated the code. What I gleaned from most of the threads it came down to the CEL only coming on due to a wiring problem, bad knock sensor or bad ECU which was quoted from the FSM. The concensus was that whatever the knock sensor was sensing did not set a code it just did what it was supposed to do in the background to eliminate the knock.

This is exactly why I haven't replaced mine. I recall reading your exploits along with others that replacing the knock sensor and pigtail in the proper location along with direct wiring to the ECU didn't fix the problem.

Thanks for your input....keep it coming.

wheelin_toyota_guy

So I have been battling the code 52 since I got my truck. I have tried everything I could think of including what people have said on numerous forums. I replaced the knock sensor twice. Replaced the wire. Still had the code... I finally looked into getting a computer but as probably most of you know reman's aren't cheap and you never know what your going to get used. So my solution was to try to directly replace the wire from knock sensor to computer. I took apart a good RCA cable cause it was shielded. I grounded the shielding to the engine next to the sensor. On the other side by the computer I grounded it to the ecu itself. The wire went from sensor to black wire on ecu. Which was c8 on my ecu. 89661-35350. Which seems from research to be a rare ecu, only early model runners and pickups... The factory service manual led me the wrong way... Come to find out, if you take the lid off it tells you on your circuit board. Anyhow, my code is gone! For those of you with a stereo system, make sure when doing this the sensor wire has a good shielding, at least what I've found out.

abecedarian

That you had success grounding it at both ends suggests you and the OP may have issues with engine and chassis grounds, i.e. the system had/has "ground loops", where grounds at one point are not electrically the same as a ground at another point.

wheelin_toyota_guy

Sorry grounded at computer only. And as far as that goes, it does not matter... Here's why, the ground is specifically part of the shield. The wire from knock sensor to computer does not care if it's grounded or not. The main reason is the shielding. It keeps out frequencies that may trigger the piazo knock sensor supplying ecu with voltage telling it that the motor is knocking. And constant that's why cel is set. Power and mileage suffer.

doublel

I've already run a direct wire from the KS to the ECU and grounded only at the ECU. Mounted a KS external and still have a solid CEL code 52. Thought I would eliminate everything prior to tearing it down and replacing KS and pigtail since others on this website have done that and still have code 52. I know I have read other posts on here where mounting a KS external has been done and it eliminated the code. Guess that is not going to work on mine.

scope103

Sorry, it DOES matter. Abecedarian is right; if you get a "ground loop" in the shield it won't do you any good.

Ground loops are more of an audiophile thing, but the knock sensor signal is of the order of that from a tape-head (or LP pickup, if you even know what that is). So it is amplified to be sensed. If your shield is connected to "ground" at each end, and there is any voltage difference between the ends, current will flow in the shield (and get induced into the signal wire). So every time the ignition coil fires a few thousand volts into the block, some current flows in the shield, and your knock sensor signal is lost in the noise.

XtraSlow_XtraCab

I've gone through this with my 22RE. It took a couple of hours to finally find a YouTube video that explains the piezo knock sensor and the wire being a frequency transmitter (knock sensors generate their own signal without electrical assistance... like plucking a guitar string).

Anyway, I'm suprised that most people really figure the wiring becomes chafed so easily! Sure it's possible, but if recent repairs involving timing (both valve or iginition) have been made then all attention should be turned to that. If someone has already said this, then my bad. I wasn't going to read EVERYTHING. Just thought I'd throw in a snippit.

My 22RE threw this code because all in all the igniotion timing was WAY off and it knocked. IMHO the troubleshooting guide in the FSM was written incorrectly. It should have included basic maintenance in the SOLUTION column. Anyway, the ignition timing had been off for a long time, BUT the spark plugs were very old and the gap had doubled... thus making a weaker spark at an extremely advanced timing... so it never actually knocked until I gave it stronger spark (new, correctly gapped plugs) but at the overly-advanced timing setting.

wheelin_toyota_guy

You must not have read my other reply. But you might not know how. To explain how to do this, you must start at the top. Read right to left as your going down the page. I hope this helps...

vasinvictor

iTrader: (3)

^ That's not necessary. I had a code 52 when I broke my pigtail wire, and mounted a knock sensor in the engine hook with a new pigtail wire to temporarily "fix" my truck til I could tear it apart and do it the right way. I know if it's been suggested yet, but some are using a coax cable for a shielded solution. Hope you resolve this.

wheelin_toyota_guy

It's been mentioned, but the reason I've used a good RCA cable is cause its a little more forgiving in being able to flex where you want it. I am ready to my swap. I know for sure this is the last 3vze I'll ever buy. I've only had 1 before this and like 6 others that had the 22re in it and I will tell you, I will take the 22re's lower power over the pain of dealing with these 3vz probs...

XtraSlow_XtraCab

Right to left?

wheelin_toyota_guy

It's called sarcasm, like your comment

some drunk guy

I'm a little confused, can someone explain the shielded wire? Looks like there are 2 wires in the wire harness to the ks pig tail connector, which turns into 1 wire on the KS. What is the shield? Is one of the 2 wires a ground?

some drunk guy

Wait.. I re read it. The "added" wire was shielded and then grounded at the ecu...