... but this one is a little different. I know what some of you guys are gonna say, read the other threads first. And I've spent hours on this site and toyotanation trying to figure this out. So I have a 1995 4runner that I am planning on purchasing through my school's auto shop and I'm doing all the work on it myself. It originally started out with a blown head gasket, so I replaced that, put new cylinder heads on it and around 1,200 worth of other parts. After I get it all back together, it has a code 52. And all of the fun symptoms that come along with that (atrocious gas milage, power like you're towing a huge trailer accompanied by hesitation under quick acceleration. Among those parts I replaced was a knock sensor (Napa Auto Parts) and the pigtail wire (Toyota Dealership). You can imagine my frustration as I spent a few months on and off working on this thing only to have to tear it back down again. I tested EVERYTHING : Resistance from block to neg terminal, continuity/resistance from the harness connector to the computer, continuity to the pigtail wire, put one probe on the body of the sensor and checked continuity to ground. It all checked out. All of the wiring seems fine. So I tore it back down again last week. But it so happend I couldn't find a torque value for the knock sensor so like an idiot I left it hand tightened and my shop teacher said that that must've caused the code to go off. It seemed like it made sense that it was a connection problem (looseness) because sometimes the light wouldn't come on for 5 minutes and it would run fine like a lot of these threads. So I tightened it right a ratchet sufficiently and put it all back together. Start it up and let it warm up then I blipped the throttle a few times and to my utter frustration, the engine started hesitating and light came on.
So where I'm at now: the car is running, and I purchased yet another pig tail (whether my current new one is bad or not) and a TOYOTA knock sensor. I'm planning on mounting the new one externally and connecting it to make sure it works but my question is where the best place is? I'm thinkin either the napa sensor is bad (unlikely, but we've gotten bad parts out of the box before) or something with the location of the sensor possibly? Just thought I'd post to see if I can get some helpful input for my specific situation from people who've had to go through this nightmare as well. Thanks guys!

 

Bump... I am going to just ground the new toyota sensor and connect it just to see if the computer will get a signal any input?

 

I'm actually having the same problem. I tried welding a nut to the engine mount engine side. Nothing. Tore it apart replaced both the harness and kn sensor and I'm still getting a code 52. Is there any other sensors that I should check that could be associated?

 

That sucks dude so you definitely feel my pain. I'm gonna mount the new sensor externally tomorrow. Any input from anyone who has done this and made it work? I'm most likely going to tear it down to put it in its proper place eventually though

 

And ben, did you check the black wire going to the computer from that harness connector with an ohmmeter? Until you do that don't bother tearing it down again you can do it without taking anything apart except for a few screws to the PCM. IIRC the terminal t goes to on the pcm is B5 I'll check the wiring diagram tomorrow. And the pcm is in the right kick panel on the passenger side

 

Tested the Napa sensor with a Snap On Vantage lab scope and got nothin. It's gotta be that sensor. Gonna tear it down again and put that toyota sensor in. If this doesn't fix it I have no clue what is wrong. Either way I hope at least some of this information helps someone at some point.
EDIT: Connecting toyota sensor and using a lead going from the sensor to ground it on the battery still caused a code 52 so I believe this is not a sufficient way to give the computer a signal so do not think your sensor is bad if you have this result from doing this. I'm gonna post my results after I get it back together with the new toyota sensor and yet another brand new pigtail wire.

 

UPDATE: tore it down and put the toyota sensor in and I couldn't get the code to set today so I think it's working normally now! That Napa sensor was also sitting in a parts box for a couple months with the other parts getting moved around and possibly dropped and if you drop these things the little crystal breaks inside so DO NOT DROP or be rough with your sensor because it might just end up not working... Glad to finally be over with this nightmare diagnosis.

 

I know this is ab old thread but was the solution really an OEM knock sensor? I inherited a 94 that had low power, poor mileage issues. Didnt get the chance to check the codes before it got torn down. I suspected a fuel problem so i had the injectors cleaned and replaced the fuel filter and pump. I haven't got it all the way back together yet but the more I read I think replacing the KS while its apart is probably best. I was debating on ordering a aftermarket KS....

 

just put a oReilly (import direct) ks in and it came on right after so im woundering the same

 

can someone help I have a toyota 4runner 1992 after doing the head gaskets now truck will not accelerate. I think the mechanic did not put the vacume hoses back properly. will be very thankful.

 

Hi im a new member can anyone help just did head gaskets on toyota 4runner 1992 but now truck will not accelerate i think mechanic did not put vacumine line hoses properly

 

Having been through the same issue, I can't say this enough, buy a Toyota OEM Knock Sensor. I tried non OEM and BAM, code 52 again. Just spend the money on a OEM KS and fix the problem.

 

This, everybody.

 

I too have tried everything except the obvious, Toyota brand knock sensor in the correct location. that has gotta be the answer. tried the remote mount, tried the new wire to ecm coax grounded shield, tried new ecm checked timing, tps and even belt timing, none of this has gotten me cleared of this damn code, truck has been returned to the the condition i received it, original wires from ecm to pig tail, "these wires passed the ohms test to began with... new Toyota pig tail and Napa sensor, original ecm.. only code is 52. going to get the Toyota sensor and install it in the correct location this week. hoping to share some results soon, I cant believe after 25 years the root of the problem for such a simple code cant be pinned down.

 

its the napa sensor, it was all ways the sensor, got the toyota oem part, didn't have time to assemble the engine till this week. got it done code gone!!!!!! truck passed California smog. i got this truck with the light on. I tried EVERYTHING,(see earlier post )finally with all options exhausted, got the right sensor. save yourself a lot of tail chasing. thanks for all the advice I got out of other threads on this site, seemed every body had come to the same conclusion.

 

This seems crazy. I have spent hours now looking for the fix for this too. I ended up buying a new pigtail and sensor off of eBay for total of about $35. I plugged in the pigtail to the harness and grounded the body of the sensor (similar to mounting it on the engine lift) and cleared the code. No luck! I have also checked the continuity of everything back to the ecu.
I am concluding the same as many that the cheap non-oem sensor is probably the problem. So what seems crazy is that there are many new KS's from $10-$45 range and then they jump in price up to $280 for oem, and there is no easy way to check the part before installing it!
So of course I'm going to try a $15 one first but thank god I'm not ignorant enough to spend a day tearing apart my engine top and putting back together to find out it is a junk part, but aside from that, it is also ridiculous that they can charge over $200 for this oem sensor. I can buy an ecu for that much!
I'm still not sure what to do because I'm fearing that maybe the wire shielding is bad and the possibility a spark plug wire is causing a bad signal.
I wish there was an easy way to bench test the Knock Sensor without an oscilloscope. Anyone?

 

do you think the valves being out of whack and clacking around would cause the knock sensor to go off?

 

I think it could but really don't know. Seems like anything that you could hear with metallic sound might affect the sensor but it should not cause a code to occur. If the sensor is working and there is a knock it will just retard the timing.
It should only cause the code to light if the circuit is bad.... open or grounded I believe.

 

No.

Almost exactly right. The code means the ECU has "lost touch" with the knock sensor. The most likely cause of that would be an open or short, but anything that interferes with the signal could do it. The sensor wire is shielded to protect it from all the EMI in the engine bay, and if that shield is lost the ECU will not be able to cull the signal from the noise and it will throw the code.

But the point worth repeating is that code 51 NEVER means "the engine is knocking."

 

so to avoid taking the engine apart could i get another knock sensor say from a junkyard and mount that to the lift hook by welding a nut onto the hook and go get a new pigtail and just hook it up that way?