runn4

I just got a 95 4runner 3.0, 5spd, 4wd a couple weeks ago and am having problems with the code 52. I understand that the problem is either the knock sensor, pigtail wiring, harness wiring to ecu, or the ecu itself. I just recently replaced the pigtail between the intake manifold but not the knock sensor. I tested it for continuity and it checked out as good.

Well i put it all back together and still code 52... It does seem to run better but that might be because of me rebuilding the injectors and putting the vacuum lines where they should go. I can't tell if its running normal as I bought it with the code.

So now i need to check the wiring from the pigtail to the ecu but am unsure how to do that and where the wires and the ecu are/go to. Ive been searching the threads but have not found a specific answer.

Team420

You cant test the knock sensor with a multimeter. You would need an oscilliscope(spelling?) for that. I had this same issue a few years back, did the same test, replaced the pigtail... rewired to the ecu, swapped the ecu with a known good one, and still had the code 52.
Finally...I had to tear it down again to do intake gaskets, and vc gaskets, and replaced the sensor while I was in there and the code went away.

Now...most ppl agree that it was the sensor that fixed the problem... but I still have half the opinion that it was the intake and vc vacuum leaks that was causing her to run super lean, and ping like mad that set off the code... Either way... it was gone after all that.

j2the-e

Quick and dirty knock sensor test: Set your voltmeter to the millivolts setting, key and engine off, disconnect the knock sensor wire under the throttle body. Stick a long extension into the valley and lightly rap the end with a hammer. You should see voltage between the knock sensor and ground. If you have a voltage reading, it doesn't necessarily mean the sensor is good, but if you have nothing, it means the sensor is dead.., If you replace the sensor, I recommend a Toyota sensor only and be sure to torque it properly with a torque wrench!

runn4

How should I test the wires going to the ecu to see if they could be bad? There was a break in the wire insulation right before the connector to the pigtail, I wrapped it in electrical tape but im starting to wonder if there could be a problem in the wireing that is preventing a good connection.

I just want to make sure it is the sensor before I replace it. I would be ok with spending the money and going through the work to replace the sensor if it was a sure fix. I just would hate to replace the sensor and be out 200$ and still have the code..

j2the-e

You would test the wire with an ohmeter from the pigtail to the ecu.

scope103

The pinouts are here: http://personal.utulsa.edu/~nathan-b...86troubles.pdf

The sensor wire shield is grounded only at the ECU; not at the block. The shield is fairly important. You can, at a minimum, check the KNK wire for continuity.

runn4

OK so on the connector there are two pins, one of the pins has continuity from to the ecu pinout but not to ground. The other pin on the conector does not have continuity to the ecu but does have continuity to ground on the block...

Is the second pin not supposed to have continuity to the block?

runn4

So I determined that the second pin/wire is for the shield.. But when checking for resistance, one end touching the pin the other the block I get continuity. Is this how it should be?
Also where does the end of that wire end up?

runn4

bump.. Can anyone please confirm this?

scope103

The brown wire in the 2-pin connector (from the ecu, which connects to the pigtail) is the sensor ground/shield. It eventually connects to ground at the cam bearing cap.

So yes, when probing the 2-pin connector that connects to the pigtail, the brown wire has continuity to "ground," which includes the block.

runn4

Thank you scope! That was driving me crazy.. So my knock sensor is most likely the culprit, I need to get one from the dealer and tear it open.


Edit: well to put this thread to an end. I changed out the knock sensor with one from the dealer and no check engine light! Thanks to all who helped me.

50kta

so how do you check continuity on the non shielded wire going to ecm....where do you probe??

scope103

Uh, what are you talking about? This is a thread about the knock sensor, and the knock sensor wire to the ECM is shielded.

50kta

how do I check continuity from knock sensor wire to ecm. ?????plug a jumper wire into the end where the plug is at the knock senor run wire around truck and put my multy meter on jumper wire and knock sensor pin at ecm to check continuity?

scope103

Yes, that sounds like the easiest way to do it.

50kta

cool thanks

djswan36

Hey 50KTA,
Any luck on this fix?