When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
yes the knock sensor wires should be shielded they look like speaker wire. maybe where it goes back into the harness the shielding is touching the signal wire. I would peel it back and repair it the right way or run a whole new wire.
the insulation is gone for about 4 or 5 inches up to where it goes back into the main harness so I can't even see where I need to in order to repair it. I may have no choice but to run a new wire. So the question now is where does the shielding land at the plug? I see only one wire at the connector so does it just end at the plug and not terminate anywhere?
Originally Posted by Ali SC3
yes the knock sensor wires should be shielded they look like speaker wire. maybe where it goes back into the harness the shielding is touching the signal wire. I would peel it back and repair it the right way or run a whole new wire.
And as you stated, this shows the shielding for the knock sensors. Awesome, that has got to be my problem, thanks again.
Originally Posted by Ali SC3
yes the knock sensor wires should be shielded they look like speaker wire. maybe where it goes back into the harness the shielding is touching the signal wire. I would peel it back and repair it the right way or run a whole new wire.
Knock sensor wiring will definitely throw a code and reduce timing from the 20 range down to 12ish, from what I logged when one of mine was bad. The shielding only runs, like you said, to about 5" away from the plug. You can buy shielded wire from any electronics place, then make sure you ground it to the ECU ground, as the ECU has a built in ground to read sensors like TPS, CPS, Knock, Cam sensor etc.
Cool build. My SC was one of the fastest on the track when I did WRL. I ran 275/40/17 crap tires as well. I've found the wider the better, I gained about 5 seconds a lap swapping to 315/30/18's. Only problem is tires are EXPENSIVE, but if your team has the extra funds for $1200 a race weekend the SC will pretty much be unbeatable.
My car with Gutted doors/hood and trunk weighed 2809lbs with 20.6 gallons of gas. Going a bit further with fiberglass doors/CF hood and Trunk LS1/T56 it weighed 2729lbs. I completely removed the entire body wiring harness which saved a good 40lbs. Think you already posted a while back in the thread with what I was doing.
Thanks for the info. I repaired the wiring at the sensor, thought I had found the issue. The copper plug in the connector wasn't making good contact with the pin on the KS so I got that bent/adjusted to make good contact and heat shrunk over the bare wiring. The wiring looked good once it got into the harness so I thought I was good. Took the car out to test, threw code 52 again. So, now I am back to completely rewiring. I looked at the wiring at the ecu and I can't seem to figure out which wire I need to replace and where the ecu ground is. Any suggestions? I had enough shielded wire left over from the stripping I should have enough to run all the way to the ecu.
I did get all the ACIS stuff hooked back up, at least it is working properly now.
Originally Posted by fried_rice
Knock sensor wiring will definitely throw a code and reduce timing from the 20 range down to 12ish, from what I logged when one of mine was bad. The shielding only runs, like you said, to about 5" away from the plug. You can buy shielded wire from any electronics place, then make sure you ground it to the ECU ground, as the ECU has a built in ground to read sensors like TPS, CPS, Knock, Cam sensor etc.
Cool build. My SC was one of the fastest on the track when I did WRL. I ran 275/40/17 crap tires as well. I've found the wider the better, I gained about 5 seconds a lap swapping to 315/30/18's. Only problem is tires are EXPENSIVE, but if your team has the extra funds for $1200 a race weekend the SC will pretty much be unbeatable.
My car with Gutted doors/hood and trunk weighed 2809lbs with 20.6 gallons of gas. Going a bit further with fiberglass doors/CF hood and Trunk LS1/T56 it weighed 2729lbs. I completely removed the entire body wiring harness which saved a good 40lbs. Think you already posted a while back in the thread with what I was doing.
Thanks for the info. I repaired the wiring at the sensor, thought I had found the issue. The copper plug in the connector wasn't making good contact with the pin on the KS so I got that bent/adjusted to make good contact and heat shrunk over the bare wiring. The wiring looked good once it got into the harness so I thought I was good. Took the car out to test, threw code 52 again. So, now I am back to completely rewiring. I looked at the wiring at the ecu and I can't seem to figure out which wire I need to replace and where the ecu ground is. Any suggestions? I had enough shielded wire left over from the stripping I should have enough to run all the way to the ecu.
I did get all the ACIS stuff hooked back up, at least it is working properly now.
I had a code 52 on my MK3 ages ago and I ended up running the shielded wire all the way back to the ecu and grounding the shielded wire on the ecu side (but not tied in to the ecu ground) I also replaced the plugs / connectors at the same time. it worked like a charm for me.
From reading the wiring diagram it shows the knock sensor grounded to the engine block. After wiring newer GTE's and standalones all sensor grounds run through the ECU, to ensure all sensors have a proper ground and readings. Here is a Supra diagram, which shows pin E2 as the sensor ground, pin 80-65.
I've re-wired/pinned knock sensors before which did not seem to fix the problem. Check out the OBDI scan software thread, that may give you a better diagnostic tool, than replacing a bunch of wiring and not knowing what the ECU is reading/doing. https://www.clublexus.com/forums/per...ger-found.html
Man that is great info. I didnt even have anything to go by to know pin numbers at the ecu so very helpful. The problem I have now is I have to be at Road Atlanta on Friday afternoon so I dont have time to do any of that OBD1 software stuff before then. I may have to just run a new wire and hope that gets it. The other thing i thought of that was done right before I started having this issue was the ecu was sent off for capacitor replacement. I wonder if something could have been damaged during that work and cause the 52 code? I will rob the ecu from my other car and see if it throws the same code. If I rewire luckily i kept all the old stripped wire from the car and found a piece of shielded wire long enough to do the job and it already has a pin that will fit the knock sensor connector.
Originally Posted by fried_rice
From reading the wiring diagram it shows the knock sensor grounded to the engine block. After wiring newer GTE's and standalones all sensor grounds run through the ECU, to ensure all sensors have a proper ground and readings. Here is a Supra diagram, which shows pin E2 as the sensor ground, pin 80-65.
I've re-wired/pinned knock sensors before which did not seem to fix the problem. Check out the OBDI scan software thread, that may give you a better diagnostic tool, than replacing a bunch of wiring and not knowing what the ECU is reading/doing. https://www.clublexus.com/forums/per...ger-found.html
I want to say the shielding is just grounded to a regular ground by the ecu somewhere. the shielding is just wrapped around the wire at no point should it ever touch the signal wire or be connected to the ecu.
you would have to unwrap the harness to get to the part of the old wire to repair. hard to say if its worth it, there is a possibility it could be form the ecu if its not working right, but since you messed with the connector recently that seems more likely. also check the other knock sensor's connector maybe you did fix this one and its the other one that is throwing the code.
All good comments. Unless the original wiring is incorrect, the #1 should be the front one and should land on pin 50 of the 80 pin plug. But, I'll ohm it out to make sure. I understand about the shielding and how it can't touch, etc. I was able to unwrap the first 6 inches or so, up to the major joint, of the harness at the sensor and it looked good so problem must be elsewhere. I am going to swap ecu's tonight to make sure it isn't in the ecu. Possible since I just had the capacitors changed, maybe something was damaged. I have the new wire ran, I just didn't want to cut in to the old one until I knew it was a wire problem.
Can someone coach me through unpinning a wire from the plug at the ecu? I couldn't figure it out. I would like to put an old connector in and splice to the new wire instead of cutting the original if possible. I would rather do that in the event it turns out to not be a wiring issue.
Originally Posted by Ali SC3
I want to say the shielding is just grounded to a regular ground by the ecu somewhere. the shielding is just wrapped around the wire at no point should it ever touch the signal wire or be connected to the ecu.
you would have to unwrap the harness to get to the part of the old wire to repair. hard to say if its worth it, there is a possibility it could be form the ecu if its not working right, but since you messed with the connector recently that seems more likely. also check the other knock sensor's connector maybe you did fix this one and its the other one that is throwing the code.
remove ecu plug (phillips screw driver), on the back you will see 2 yellow covers over all the pins.
use a small flat screw driver or just pry the yellow covers off, there are spots on the edges for you to do that.
now that the covers are off you will see all the pins from that side and each pin will have a locking tab that is now exposed. you need a small flat screw driver again (like the very small ones for glasses), and lift up on the plastic locking tab next to the pin you want to remove, and while you are lifting with the screw driver, pull softly on the wire and it should slide right out.
top tip: do not lift on the locking tab too agressively or you will break it, and then forever have a loose pin. loose pins = loose connections = lots of problems. take your time, do not break the plastic locking tab. if the wire is not sliding out then you need a thinner screw driver or you are not lifting the tab enough or properly. once you do one its really easy after that.
to put it back in just slide the pin in and you will hear a "click" when it locks. no click = no lock = bad connection. once you hear the click and are done, put the yellow covers back on and then you should be good from there to plug back into ecu.
This also applies to almost every toyota connector in the car, they all have locking tabs next to the pins, and they all have a cover that hides them except they wont all be yellow covers, some of the "covers" actually go way into the connectors and you have to pull them out with needle nose pliers or work them out with the handy flat screwdriver (I have one I specially use just for pins). the locking cover is always easy to spot its usually a different color (white or yellow or grey).
Once again, thanks. I understand now from your write up, I wasn't taking the yellow covers off. Will update after doing this.
Originally Posted by Ali SC3
remove ecu plug (phillips screw driver), on the back you will see 2 yellow covers over all the pins.
use a small flat screw driver or just pry the yellow covers off, there are spots on the edges for you to do that.
now that the covers are off you will see all the pins from that side and each pin will have a locking tab that is now exposed. you need a small flat screw driver again (like the very small ones for glasses), and lift up on the plastic locking tab next to the pin you want to remove, and while you are lifting with the screw driver, pull softly on the wire and it should slide right out.
top tip: do not lift on the locking tab too agressively or you will break it, and then forever have a loose pin. loose pins = loose connections = lots of problems. take your time, do not break the plastic locking tab. if the wire is not sliding out then you need a thinner screw driver or you are not lifting the tab enough or properly. once you do one its really easy after that.
to put it back in just slide the pin in and you will hear a "click" when it locks. no click = no lock = bad connection. once you hear the click and are done, put the yellow covers back on and then you should be good from there to plug back into ecu.
This also applies to almost every toyota connector in the car, they all have locking tabs next to the pins, and they all have a cover that hides them except they wont all be yellow covers, some of the "covers" actually go way into the connectors and you have to pull them out with needle nose pliers or work them out with the handy flat screwdriver (I have one I specially use just for pins). the locking cover is always easy to spot its usually a different color (white or yellow or grey).
UPDATE
So the new wire did not solve the problem. Only thing left was both old and new knock sensors must be bad. I robbed a sensor from my other car, no 52 code. I hate when that happens.
With the knock sensor working and the acis valve hooked back up the car has been strong this weekend. Bring on Daytona in April.
Awesome, Glad you got it sorted out. I ohmed both knock sensors of a previous SC which came back fine. That's one of the cars I re-did the wiring and still had the code sporadically.
I ended up swapping another engine or selling it I can't remember. In the future I will just replace the sensor and connector if I ever have this issue. Now thinking about it the shielding may not play as big of a role in the older ECU's, as I've seen a harness with no shielding reading the knock sensor fine and throwing no code. It takes me a while sometimes to remember all the little quirks and work arounds I've done over the last 10 years.
I've went through so many engine combinations etc, some of these little issues end up getting fixed by swapping cars or engines out. I've only had 15 SC's so far.
Originally Posted by RXRodger
UPDATE
So the new wire did not solve the problem. Only thing left was both old and new knock sensors must be bad. I robbed a sensor from my other car, no 52 code. I hate when that happens.
With the knock sensor working and the acis valve hooked back up the car has been strong this weekend. Bring on Daytona in April.
02-19-16, 10:37 PM
If shielded, then that's it
