Team420

Found some info on testing a knock sensor, I performed the test and it seems my k/s is functioning...still getting the code 52 though, and I assume it is in the ground, as I do have continuity from the connector to the ecm, there is also continuity between the ground and neg batt terminal( not sure if thats good or not). Any way... here it is

"About the only way to test this sensor is to over-advance the timing, attach your digital meter (AC scale), and take the truck for a test drive. If the sensor is working, you should see AC readings that correspond to the pinging you hear."

found on this page http://www.asashop.org/autoinc/JULY/techtips.htm

I advanced my distributor as far as it will go, and still didnt hear any pinging or knock, but the multimeter did jump around as I accelerated, and only minimally at idle... I would assume this means that the k/s is functioning, turn the truck off, and the meter reads 0.
Hopefully someone else will chime in to verify that this is a legit test of the k/s.

Team420

Just curious but... Is it possiblr that over advanced timing could cause the code 52? And if so, why dosent the fsm mention that as a possible cause. Just decided to check my timing and it's at 25 btdc...I can only turn it down to about 5 or 8 btdc with the distributor, cant figure out why that would be, seeing as the dist has never come off the truck. Any advice is greatly appreciated, as I have been racking my brain on this for several weeks now.

toytech76

no. over advanced timing wouldnt cause that. Your timing is probably off because your tps is out of adjustment. On any 3.0, if you go in to fix a code 52, I would replace the sensor and the wire since it is alot of work to get to it

refried

Quick knock sensor test
1 check timing
2 watch timing marks as you tap on block with hammer
3 did timing retard? if it did your knock sensor is working

Team420

I read that tapping on the block will not retard the timing, it is not the frequency the k/s is looking for, I agree that the tps is prob out of whack, as when I jumper the diagnostics terminals, the idle does not drop, and I did not think overadvanced timing would set the code 52... afaik the code 52 just means there is a bad connection between the k/s and ecu, or the k/s is no good. I guess i'm going to try to rewire the k/s to the ecu using coax cable(cable tv wire) and ground both ends to the block. hopefully that will do the trick. Anyone know if the above mentioned test is an accurate way to test the k/s? and what would be the proper way to test the connection to the ecu?

Team420

Ok, so I rewired all the way to the ecu, and grounded to the neg batt terminal, still code 52!!
I thought these things would throw a code after 1700 rpm, revved it in my garage held at 2500 and no "cel" brought up to 3000, still no cel,, so i decided to take it down the road a bit, and sure enough as soon as I move 10 ft, the cel comes on...52.... Why does this thing not light the cel when I rev it to 2500 rpm, but yet lights it as soon as I start to move? I am starting to think that maybe I have an inaudible knock that may be causing the k/s to generate too much signal, and the ecu is mistaking it for interference. Any one wanna chime in as to weather or not that is possible? I can see that there is voltage coming from the knock sensor when I drive it down the road, but I have no idea on what it SHOULD be . I am running out of options, and I guess i am going to spend the $175 on a sensor that most likely will not fix my problem. But first, I am going to get the tps sorted out, and get my timing to where it should be, to see if that helps.

Team420

No luck...got the tps adjusted... and still code 52.... so I gues I'm gonna order the sensor, and hope that fixes it... I am very doubtful that it will, When I rev to 3k rpm, in driveway...no cel...go over 1700 rpm while under load...cel pops on ev time...but yet I hear no knock.....

to4menon4u

you might wanna replace the wire running to the sensor as well those are know to go bad.

Team420

yeah...I replaced the pigtail that runs from the k/s to under the throttle body, that didnt fix my prob, so I replace the rest of the wire all the way to the ecu... still code 52, then I checked my timing (just for s and giggles) and noticed that it was 28 btdc, and that the tps was out of spec, so I adjusted the tps, and now...it runs better...but still code 52...the only option I have left is to replace the k/s itself, even tho the test I ran on it tells me it is producing signal...I just donr know if it is too much or not enough, or if there is some underlying problem, also...I replace the ecu with a known good one.

to4menon4u

well this may be a shot in the dark but this is what i think is happening to my motor as well. if the knock sensor is designed to adjust the engine timing to prevent engine knock. what if your engine is producing a slight knock and the sensor is doing everything it can to prevent it? i have a slight knock in my motor and my timing goes crazy from time to time.

Team420

Thats exactly what I was thinking, however, everyone I have talked to about this, says that code 52 means the ecu cant see the knock sensor, bad circuit, also..I have never heard a real knock coming from my motor... it used to ping every now and then with 87 octane, but now I run $uper and it sounds ok.
I have a knock sensor coming...so I guess we'll see, also, I'm like 99.9% sure I have a vacuum leak, which I hope to fix while doing the knock sensor, Maybe that is not helping things? Dunno...drawing straws at this point.

Team420

Yes!!! My advice to all is to replace both at the same time...at least that way you can rule them both out.

Team420

and yeah...my timing was like 25-30+ d btdc, after the tps adjustment, it is now down around 15, any lower and it has no power, higher...and it still wont ping..at least not that I can hear.... driving me insane

Team420

Hows this for a crazy theory, I read somewhere that if you have a stuck open egr valve(specifically on 3vze) it will make your engine knock, and I'm not sure which code I got first(I think it was the 52). Now I get code 52 within 2 minutes of drive time, and 71 within 10 miles or so, I was waiting till I figured out the k/s problem to fix the 71, but now I am thinking that the 71 is causing the 52... Am I crazy? Well to see, I am going to block off the egr completely and throw a 10k resistor in, who knows maybe it will fix both, and if not, then I am going in to change the k/s. Starting this project in a couple hours.

bob hennig

did anything work for you? What found? bob

luder

just curious. ive read ten of these same senarios now and everyone avoids replacing the knock sensor and no one can figure it out. its such a simple circut, maybe the knock sensor is bad? save your money and quit messing with other things it sounds like your going to have many problems by the time you figure out that the knock sensor is bad. not trying to be rude but it is what it is and thats what it is.

Innervision

The knock sensor on the 3vze engine is burried deep in the Bowles of the block. It's not a quick fix. that is why so many people exhaust every option before removing the top half of the engine to get to the sensor.

luder

i see, sorry i dont know what im talking about, but seriously sounds like a knock sensor went bad like i said simple circuit. where is it located i would assume removing the oil pan would bring you access to it but like i said dont know where or what im talken about on the 3vze. what i do know is that toyota has made it a bear to work on just about anything. even my 22re is somewhat a pain coolant lines galore and vacume hoses like crazy did i mention the hidden bolts everywhere!! There not just hidden there hard to get to too..plus its a four cylender in an suv and theres no room under the hood what so ever. I always respected toyota for reliability and build qaulity but after reading reviews and tech forems im starting to second guess. i havent even got to drive mine yet picked it up for cheap with what i thought was a bad head gasket turns out timming chain wore through the cover anyways got it all fixed but crushed the knock sensor connector also the tv valve go to your parts store and try to find one of those! damn dealer parts!!!!!

Innervision

The sensor is under the intake manifold. You have to take off the plenum,fuel rails, injectors and intake and it is located down between the heads. Poor location for a sensor. There is no way to get to it with out basically taking the top end off the engine. Not to mention the wires are pinned between the intake manifold and the block in a small grove. I don't see how these wires keep from melting.

But I do agree that most of the time changing the sensor or wires is the cure all.

bob hennig

I have had same exact problem after rebuild, low rpm, light throttle load conditions, code 52 set, Heavy throttle and I can hold code off as long as have foot into car. I have replaced the sensor, wire, back to the computer. I know senser is working tested with Millivolt tester and read bet 200 and 400 millivolt , but under partial load, light load, very wweak signal. I think problem deeper. Original sensor may be out of range for modern comnponants, fuels. Am testing different range sensor. Will let know what I found Read code 52 is there really a fix. amazing problem, lets beat it!!!