Team420

So I have had this code for over a year now, it really makes the motor sluggish.
I have replaced the pigtails wires, tested the knock sensor itself, and rewired it directly to the ecm.... still code 52.
Now.. this truck also leaks oil at the valve cover gaskets, and that got me thinking... could that also be a vacuum leak? I think a vac leak cause it to run lean and possibly knock... but you cant hear it..which leads me to believe the sensor is actually working, its just not getting the right signal, thus triggering the cel. Does this sound right to anyone? I have been all thru it, and cant find any vacuum leaks anywhere else... I also had a cel code 71(i think) for the egr(another reason I think vac leak)... but I just bypassed it, hoping that would fix both problems.....but it didnt. Someone tell me I'm on the right track here....I gotta get this thing road worthy again, the intrepid has lost reverse....

jpmountainboy

your timing may be too advanced causing knock. its hard to set it correct when its always retarding the timing so it can be a beech to really tell where your timing is...physically advancing it against the ecu retarding it.

I wonder if under test circumstances it seems like it is working, but is actually too sensitive so it always throws the code and retards the timing.

i cant believe you have driven it that long with that code...mine ran like SH%T!!!

Team420

lol... actually...it dosent run too bad, just takes a bit longer to get to speed, and downshifts a lot easier now. I'm pretty sure the timing is ok, This didnt start after I did a t-belt or anything... one day, driving home the cel came on for about 5 min, then went out.... didnt see it again for about 2 mos, then it came back and has been there since. I did check timing, and it was set at 8* btdc, which according to the emmissions label, is right on.

I was wondering the same thhing about the sensitive part, which is why I have a new knock sensor for when I rip it apart.... only thing that stinks about this is.... When I replace it(and valve cover gaskets) I wont know which fixed the problem...assuming either fix the problem.

BTW...I havent driven it in 8 mos, it was buried under 5 ft of snow till 2 mos ago....lol

*EDIT* again...lol Also forgot that I had the high/loping idle before all this, I adjusted that and now she idles fine. hell, after 8 mos of sitting, she fired up on the first crank.... I love these trucks!!!!

sb5walker

If your knock sensor is good, and it has a solid connection to the ecu, and the block has a solid ground, and the ecu is receiving a good Ne signal from the distributor, and you're still getting a 52, then probably it's an ecu issue. Seems to be a number of people with code 52 who have checked everything and still get the code. Could be something like a bad cap, or possibly a bad transistor, in the ecu - our ECUs are at that age where electronic components can start to fail.

Check resistance between the block and the neg batt post. Should be very low - only a few ohms at the most.

The other thing I would do is check resistance on all three signal coils in the distributor, and check signal rotor clearances on all lobes, if you can fit a feeler gauge in there. Those are the crankshaft position and camshaft position signals that the ecu uses to time spark, and if those signals are messed up, it will mess up spark timing and advance. Make sure the connector is clean and no pins are pushed back in the connector. Or you could just try a known good distributor.

If the Ne signal is good and has a good connection to the ecu, then the next step would be to try a different ecu. Make certain it has exactly the same model number, otherwise something won't work.

phranticness

The cause of your knock sensor code is the dissconected EGR system. The EGR system not only reduces NOx emmisions, it also reduces pinging by lowering the combustion temps through dillution.

make the EGR system work as it is supposed to and your CEL will stay off

sb5walker

Code 52 doesn't come from excessive pinging, it comes from the lack of a ping signal, such as would occur with a bad sensor or bad connection.

But fixing the EGR would stop the code 71, unless it was caused by a bad egr temp sensor. Fixing the EGR would also help keep combustion temps down as phranticness mentioned.

Team420

This is what I was looking for.... thank you!! I am 100% positive its not the ecu... I have 3 in the garage that I tried with the same results from all, I even tried them in another truck and didnt get the code. I will check it out.

I got the code 52 before the egr was blocked off...I blocked off the egr thinking it may have been stuck open causing a vacuum leak... It was not the problem. I do however at this point know there is/are vacuum leak/s, and I'm working on those... was just wondering if one had anything to do with the other. I have had numerous people say that code 52 is ONLY caused by no signal goin to the ecu from the knock sensor.... but I have also had a few respectable(afaik) techs tell me that it could be caused by excessive knock....

sb5walker

One other check would be for continuity between the neg batt post and terminals E01/E02 on the ecu: those are the ecu's engine grounds. You can use a jumper cable to extend the neg batt post into the cab for testing.

Good luck - if you manage to solve the issue, I think there will be a lot of people interested in what did it.

Team420

hmmm.... I THINK, I checked that a while back, but am not 100% sure...thanks, will check it out.

Team420

Thanks... I WILL solve the issue.... just a matter of time and $. Like I said tho... I'm replacing a bunch of things while I have it apart tho... so it will be hard to know what does fix it...

Nashman00

all right the infamous code 52 it pretty easy to fix

when you re wired it to your ecu did you use a shield wire ?

you do not have to use the stock connector ether just use a male flat blade crimp connector and makes sure the sure to ground it at the ecu as in shielding

i fix these allt eh time the stock crimp is junk and case this code that or a power wire causing the signal to distort

Team420

Finally decided to get this rig goin again. My p/u has low compression on cyl 3, and I figured this would be an easier fix.

I dont know what fixed it, but heres the list of stuff I did

1- new knock sensor
2- valve cover gaskets
3- new vaccum lines, a bunch of the old ones were cracked, and I couldnt tell till I got it apart.
4- pcv valve, the old one was nasty and stuck open...couldnt have helped any...
5- used rtv to seal the intake mani, and tb. The old gaskets were not all that good, and may have been casuing a vacuum keak.

At this point... with all the vacuum leaks I had... I'd have to say it was all the unmetered air getting in there that was causing me to run way too lean, and knock/ping, thus setting off the code, but I guess it coulda been the knock sensor itself. The truck actually jumps when I mat it now, and gets up to speed quicker than my 5spd, It feels like a brand new truck!

So to all you guys with code 52..... Mke sure you have NO vacuum leaks!! And if you do tear the mani off to replace the pigtail wire...Make sure you replace the knock sensor while your in there... I replaced just the wire last time, and it didnt solve my problem. so I had to tear into her again, and do it right.

Hope this thread helps someone.

BTW.. the valve cover on the driver side was leaking really bad... like a quart every 200-300 mi, I assume that was a huge vacuum leak, and casued most of my problems.

Marc Lindsey

i have same issue changed wire and sensor still code 52 also changed timing, spark plugs, wires, cap, rotor, radiator, fuel injectors, ecu, egr. only thing i have left to try is engine wiring harness and going to start that tomorrow unless anyone else has any input please call any time i am frustrated and broke Marc 401-450-6698

AZSPEED

Caps in ecu go bad. Take your ecu to someone who knows how to replace the cap on the knock sensor circuit it is like a dollar part if that. Code 52 has nothing to do with a vacation leak......it is the ecu saying it does not see the knock sensor....

T.j. Mackmer

This is my first post so pardon me if it is ot clear. I just bought a 1990 4runner that has code 52. And with as many forms I have read they all say it has to do with the ecu not hearing from the sensor. So I bought a new pigtail and sensor. I put the sensor in the lift hook just to get my power and fuel milage back until I have time to do it right. Code 52 still. So I tested from pigtail to ecu. Had continuity. Bought a new ecu still code 52. Engine ground is also good. Is it because I bought a 30 dollar aftermarket knock sensor instead of a 200 dollar one? All feedback appreciated.

scope103

If putting the knock sensor on the lifting hook would work, why would Toyota bury it under the lower intake manifold? This suggestion comes up all the time, and I don't believe it will ever work.

I think you're going to have to install the knock sensor correctly.

Good luck!

T.j. Mackmer

So the cheap knock sensor should not be a problem then?

T.j. Mackmer

I have had the upper intake off twice not looking forward to doing it again. Either that or I am going to sell the pos to buy the parts for my 1985 toyota pickup with the unbeatable 22r.

your-real-dad

Posting here after the fact for posterity of future generations that encounter the dreaded code 52. I replaced the pigtail and sensor on a rebuilt 3vz. Code 52. Bench tested the old sensor by placing it in a vice and whacking it. You get maybe 12mV out. Tested the sensor in the truck; same output spike. Ran a shielded cable back to the ECU, no help. Bought a used ECU for $100, no joy (anyone want to buy a used ECU for a 3VZ-E?) Mounted the old sensor, known still good, to the engine hoist hook with the shielded cable and it worked! But I don't trust it to sense all pings when located on the outside of the block, so I spent an entire day and pulled the new sensor out and replaced it with my old Toyota brand sensor. Now everything is fine. The moral of the story? Don't buy the $14 knock sensor off of Amazon... All the OEM numbers matched up, and I felt safe buying it because the site says ASIN, which I confused with AISIN the trusted OEM supplier, not ASIN (Amazon Standard Identification Number...duh..). Went back to the supplier and noticed several reviewers reported the same problem, but they are still "selling them by the thousands", according to the vendor. I don't usually go with Toyota brand parts because of the expense, but in this case it cost me 5 full days of trouble-shooting and replacement time!

AZSPEED

Sorry to say I bet it comes back, these computers are 20 plus years old and the caps and electrolytics are getting old. Not a electrical engineer but my friend is who tested and repaired it, he said most vehicles from this Era will have similar problems with capacitors and such on the computers. When you are talking about such weak signals to begin with it doesn't take much for these components to be out of spec, the cap on my computer was 23% off from the rest of them he replaced all of them with new ones. Wasn't even 5 bucks worth of parts.