808nickh

So, before i posted this thread, i did allot of reading and im not sure sure if im doing this right but im at a stand still on what to do. The truck is an 87 toyota ex cab 4x4 that i bought from another member on yota tech. when i bought it, it was throwing two different codes and the truck was running really weird. It was throwing a 51 switch signal, and a 52 code knock sensor signal. I pulled the valve cover to check the mechanical timing and it was off a tooth that would explain the 40+ degrees advanced it was running. I put it all back together with new injector o-rings and gaskets on everything. Got it started and timed correctly and that must of cleared the code 51 because i no longer have it. As for the Code 52 its still there, this is were i get confused i was reading through this pirate thread. http://www.pirate4x4.com/forum/toyot...ck-sensor.html and my wiring seems good, and i replaced my knock sensor with a used junk yard replacement and its still throwing the code i tryed pulling the ecu out of my 85 4runner which is also a 22re and the truck wont even start with that ecu. Is there something im over looking?

JustinTime

Are you sure the knock sensor from the yard was good? You checked resistance and got infinite (indicates good sensor)? Did you trace the wires and make sure they were good going to the ecu, too?

808nickh

im not 100% about the knock sensor from the j-yard i can pull that one out of my 4runner that i know is good and conferm, but yea i checked all the wireing to the ecu, the resistance is infinite. What i dont understand if the knock sensor is bad why is it when i reset my computer and drive it the code doesnt appear until im around 2k rpms??

JustinTime

Ok just to clarify, you unplugged the wires at the ECU and got infinite and tested using the procedure in the above link? Basically what you are looking for in all the steps listed is that the sensor itself should read infinite. You can also test the continuity of the wires by unplugging the wires at the ECU, unplugging them at the knock sensor, then jumper the wires (make sure you do this well) at the knock sensor, then test resistance between the two wires at the ECU. You basically just make a big loop and see if the loop has any breaks in it.

If it tests OK, then you are down to the ECU and sensor. If the loop reads high resistance, you have a break somewhere in the wire. My bet is still on the sensor though. Those things are freaking expensive...

fdp101452

When I was having code 52 trouble, I could clear the code and it wouldnt come back until I reached 2k rpms. I was told by a Toyota mechanic that was how it was supposed to work, the code wouldnt reappear until 2k. I finallly ordered a new knock sensor from Toyota and replaced it. I also ordered some shieled wire with new ends and replaced the wire at the same time. That combo cured my problem, but I dont know which of the two things did the trick. You can still get the wire ends from Toyota if you decide to go that way. Hope this helps......regards.....Rick

scope103

Code 51 just means that the A/C switch was on when you tried to retrieve codes. http://personal.utulsa.edu/~nathan-b...85diagnosi.pdf It's not a "trouble" code, just used for diagnosing switches. Don't worry about it.

Remember that code 52 means "I haven't heard from the knock sensor at all." It doesn't have anything to do with timing or whether the engine is knocking. JustinTime gives the correct procedure for checking the wiring.

Keep in mind that the knock sensor signal is very small, and the engine bay is an electrically noisy environment. So the knock sensor wire is shielded, and the shield is connected to ground only at the ECU, not at the sensor (so you can't make the loop at the sensor; that's a one-pin connector. You can make the loop at the pigtail.) If the shield is not grounded (or has a long piece missing, like someone tried to replace part of the wire with non-shielded wire), you can have continuity onthe signal wire but the ecu can't pick the signal out of the noise.

Scirocco16v

I had the same issue as fdp101452... I just replaced the wire though and was cured (I had brittle wires with other systems seemed the logical step)

808nickh

Thanks for all the quick responses guys im gonna be swapping out the knock sensor in my 85 tomorrow morning. I also found a full passanger side harness out of an 86 22re i had laying around so if its wiring thats the issue i got that covered. This problem is becoming a real PITA.

808nickh

So i installed the known good knock sensor out of my 85 and still nothing.... so looks like im down to wiring or ecu im gonna get some pics a post them also c if that might help

j2the-e

Not likely the ecu. They so very rarely have any issues.

808nickh

This is exactly what my friend said, i would think that if my ecu was bad i would have other problems as well not just the knock sensor. After my wheeling trip this weekend i plan on pulling it apart and replacing all the wiring i have the whole passanger side harness.

808nickh

Ok Guys finally got picks up for everyone ive had a real messed up schedule at work and havent had the chance to work on it.

Here is a pic of the 18 pin connector on the 88 pickup thats throwing the code.


Here is a pic of the 86 4runner donor harness that i have


But the Knock sensor plug for the donor harness is pretty beat down


I guess im not sure if i should change the whole harness or just the knock sensor wire itself?? as u might notice the 86 4runner ecu plug does not have as many pins as the 88 pick up ecu 18 pin plug.

808nickh

so that last picture i found out was not the knock sensor connecter. The connector was actually in really good shape! so last night i hooked it up (just the wire) to the knock sensor drove around the block and the light came on. The only thing im not certain about is the wire itself the donor wire actually has black insulation with an additional brown insulation around that. In between the black and brown insulation there is like loose steel stranded wire?? it was hooked up to a few other wires on a different connector to the ecu. does this need to be hooked up like this?? if anyone could shed some light on this it would be greatly appreciated. thanks

scope103

Yes, the knock sensor wire is shielded. The shield is connected to ground at the ECU, and not at the other end (engine block).

I'm not sure what your question is.

808nickh

ill have to post up a picture of it im not sure how to explain it but the knock sensor wire at the ecu was connected to a different wire going to the ecu also by what looks like stranded steel in between the black and brown insulation.

808nickh

so regarding the knock sensor wire this is what i was referring too, when i removed the knock sensor wire from the 86 harness this is what it looked like

This is the Jumper wire already installed in the truck but as you can tell the steel braided insulation is sticking out away from the wire itself.



The steel braided end was connected right here with the brown wires u can see the crimp were they were all together at one point



Now my ? is when using this jumper wire method do you need to connect the steel braided insulation or what ever that is to the same area? or is that not needed?