Knock Sensor Rewire Write-up (code 52)

[Boosted Supra]

Authored by: Manny Akim (Boosted Supra)
Purpose: To clear code 52, also known as Knock Sensor; restore ECU from “Limp Mode”.

Tools Required: Wire strippers/cutters, Soldering Gun, Electrical tape, Jeweler's screwdriver(s), and Socket tools for starter removal (if required).
Parts Needed: Coax Cable (RG-5, RG-6 or RG-58), 16 or 18 Gauge Wires, Barrel Splicer’s/Crimpers, Wire Looms, Terminal Connectors.

Skills Required: Electrical splicing/soldering and Mechanical knowledge.
Pictures were taken by Larry Anderson

Let’s begin:


1. You need to purchase new KS wire connectors from Toyota, you’ll need two of them if plan on re-wiring both of your sensors. Call Jeff Watson at Champion Toyota (800) 327-2087, and give him these part numbers 82219-89103, he'll know what you're talking about. Also get some standard RG-6 (thicker) coax cable or RG-5 (thinner and easier to work with) coax cable. If you can find some stranded core coax (RG-58) cable it will make your life easier. Why coax? Coax will shield the knock sensors signal from any electrical interference. Get enough cable so that you can rewire both KS sensors from the driver’s side of the block to the ECU (measure and do the math). Also get some 16-18 gauge wires for the grounding part of the KS rewire.

2. After receiving your KS connectors (it's a wire that is about 1 ft long that has two connectors in each end). Cut off the end you don't need and cut off the access wire. All you need is the KS connector. KS connector is the round connector like this:


3. You’ll need to slide the rubber piece (use small jeweler's screwdriver) from underneath the KS connector. Next, you will have to use the small jeweler's screwdriver to lift the notch on the top end of the connector to slide/remove metal conductor from the bottom of the KS connector, which the wire is connected to. It should look like this when you’ve successfully separated the metal conductor and the KS connector.''



4. You have to solder the coax cable onto that metal conductor, cut off the wire that's already on the metal conductor (cut off all of the wire). Now you just have a metal conductor with no wires attached to it. Try to clean off all the excess stranded wires.

5. Strip back the coax cable to expose the braided wire and the white insulator, which has the center conductor in it. Peel down the braided wire so it's nowhere next to the center conductor or the KS connector, peel down enough so that you could attach the 16-18 gauge wire onto it.

6. Before you solder the coax cable, remember the rubber piece you took off earlier? Slide that rubber piece all the way down the center conductor white insulator. Now, you can solder the coax cable onto the metal conductor. Make sure it sits properly when you solder it. Also make sure you don't leave a huge solder bump, if you do, you won't be able to slide it back in the KS connector. Once the metal conductor is back in the KS connector, you can slide the rubber piece up to KS connector. Repeat all steps for the other KS connector. It should look like this:



7. Take your 16-18 gauge wire and splice/join it to the braided wire, put enough length so you can find a good grounding point in the engine bay. When prepping your KS wiring, choose which side you want to ground it. Ground it in the engine bay or the ECU location, PICK ONLY ONE location!! Connect a terminal connector on the other end of the 16-18 gauge wire. Repeat this for the other KS connector. Connector should look like this when it’s complete:



8. 86.5-88 MK3's, you do not have to remove the starter to get to the rear sensor. 89-92 MK3's, you have to remove the starter to get to the rear sensor. To get to the front sensor, just remove alternator and you should be able to see the front sensor. Please remove the negative terminal of the battery before removing the alternator; I don't think you want to short out anything if a tool gets in contact with the alternator and the battery. Be safe or else you're going to have some blown fuses.

9. Connect the new-made KS connectors to the front and rear sensors. Choose a good grounding point in the engine bay, intake manifold, firewall or even on the block. Ground both of your braided grounding wire at the location you choose. Run the KS wire along the engine harness and through the firewall, remember to use wire looms to protect your coax cable. There is a big round rubber piece, just remove it with a screwdriver so you can run your KS wire to the ECU.

10. Remove the glove box and plastic black cover to expose the ECU. Pull the KS wire through.

11. On this side of the coax cable you strip the wire again to expose the braided wire and the white insulator. Peel down the braided wire and tape it off unless you choose to ground at the ECU location, strip the white insulator to expose the center conductor.

12. You have to find the KS wire coming from the ECU harness. There are three ECU harnesses connected to the ECU, the one that has the KS wire is the harness in the middle. Even if it's not on the middle ECU harness, you should be able to find because it's the only two transparent wires out of all those three harness wires (for all MK3yrs). DO NOT cut the two wires at the harness, cut it at the furthest point away from the ECU harness. You should have about 5 to 6 inches of KS wire on the ECU harness.

13. Strip enough of the KS wire so you can splice it onto the coax cable. You can use barrel splicers from RadioShack and crimp them together. Or you can also do it my way, I used environmental splicer’s (Military Grade). Here’s a picture of the splicer’s I am talking about. The ones in the back are standard barrel splicers. The environmental splicer’s crimp just like the barrel ones but it has a tiny hole on the top to drop in solder for a perfect splice. The plastic tubes next to them are shrink wraps. Looks like this:



14. If you choose to ground at the ECU location there should be a 12mm or 14mm bolt on the right side wall. It should be about 8 inches below from the ABS ECU (if you have ABS), it's the only 12mm or 14mm bolt there; that will be your grounding point.

15. Replace the glove box, Alternator and Battery. After doing so, Reset your ECU by pulling the EFI fuse, wait 20-30 seconds. Replace the EFI fuse, start your Supra up and take her for a ride. Go WOT and feel the difference! You’ll notice the car does not feel sluggish anymore. Car will be able to surpass the 125mph limit that the ECU retards. Gas mileage will also increase due to the fact that the ECU will NOT be in “limp mode”.

16. If your code does not clear, you could probably have one or two bad Knock Sensors, or you made a mistake in the wiring (if you followed my directions carefully, you should not have made a mistake in the wiring). If you have a bad Knock Sensor, find a used one or call Jeff Watson at Champion Toyota in Houston, TX. Purchase only one new or used Knock Sensor, this way you can substitute either the front or back Knock Sensor with the new or used one to determine which one is bad.

This procedure should take a first timer about 2hrs more or less, depends if you have to drop the starter or not. Hope this helps, Good Luck.