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Discussion Starter #1
I know several board members have had problems in the past with getting a check engine light when removing the TRAC butterfly out of the throttle body with an OBDII ECU. I recently did this mod using the HKS TRAC elimination kit and I ended up with a check engine light after completely disconnecting both the sub-TPS and TRAC motor electrical connectors.

The reason for the check engine light is because the sub-TPS is unplugged, which is done to remove the hesitation at light throttle and throttle tip-in. The reason for the hesitation is because when the sub-TPS is plugged back in AFTER the TRAC butterfly is removed, the spring-loaded sensor has moved to the CLOSED position. The ECU thinks the TRAC butterfly is in the closed position and this is what causes the hesitation.

I have a 1998 Supra with OBDII ECU. I performed the mod below and plugged the sub-TPS back in. I get NO check engine light and NO hesitation. Enjoy!

I have seen in the past where some people have successfully (and unsuccessfully) tried to clear the check engine light by installing resistors into the sub-TPS connector. While this may work, there is an easier way. I am now going to plagiarize some text from Jade Supra who told me how to do it. Here goes:

"If you are facing the motor (from the front of the car), on the left of the throttle body is the TPS for the trac control. Remove the two screws holding it in. Once removed, you can see how the inside rotates. There is a spring in there that causes it to stay in place. The only direction you can rotate it is to the "open" position. Just disconnect that spring and rotate it to the "open" position. It'll stay in place by itself now. Then you can use some hot glue or whatever to make sure it doesn't vibrate down to the "closed" position which causes the off-idle hesitation. When you put it back on, plug it in. There will be no more check engine light."

I did not find the spring easy to remove, so I just rotated the sensor to the open position and then crammed two pieces of round, solid rubber bungy material I had on the workbench into each of the rotating "tracks" so that it could not rotate back to the closed position.

I'm one happy camper after doing this. Now I just need to get my O2 Fooler working!
 

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Discussion Starter #3
The HKS TRAC delete kit works on both auto and 6-speed cars (they have the same throttle body; nothing is different)

I have heard that on OBDI cars (which is what you have), that you do not get a check engine light like the OBDII cars do, but you will get a mil code stored. No big deal really.
 

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o2 sensor

If you get your o2 simulator working let us know. I have a 98 with the o2 sim and I still get the Check light. It is driving me crazy. I have tried 2 units as well just in case. It looks like it is installed right, blinks like it is supposed to but the check light still comes on and it still throws the second O2 sensor code.

Reed
 

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Beau, did you notice any difference performance wise with the HKS TRAC Elimination Kit? I haven't seen one of these for sale in a LONG TIME - ever since we figured out how to disable the TRAC for free. How much was it and where did you get it?

If you have any questions with the OBD2 fooler just ask. I put one in my car recently. It's only 3 wires. Tap ground, tap positive, and cut and connect the signal feed.


John H
 

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Discussion Starter #6
rhibbs - I'm going to trouble shoot my O2 fooler soon. When I tested it, the voltage would oscillate between 2.xx to 6.xx if I recall correctly. It is made by Casper Electronics. However, I was looking at the description of the codes from Toyota and it says that the ECU will throw a code if the voltage drops below 7v from the rear O2 sensor. I wonder if this is the problem.

John - I can't say I noticed a difference in performance with the butterfly removed, but I wanted the peace of mind knowing that the non-operations butterfly was not disrupting airflow any longer.

I too had not seen one for sale for awhile. I guy I met up at Real Performance Motorsports (Josh Smith) told me he had one lying around and I could have it if I wanted it. I said yes! He's into Supras and Mustangs; JPI just finished putting a fresh 2JZ-GTE motor in for him.

I may take you up on the O2 fooler help John. Is your's made by Casper's? When I got mine it seemed like one of the wires was in wrong, so I pulled it out and repositioned it . Perhaps that was my problem. I thought you posted in another thread awhile back that you never got a check engine light when you put your downpipe on? People were surmising that perhaps in 1996 the rear 02 stuff was not yet working on the OBDII ECU.
 

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"I may take you up on the O2 fooler help John. Is your's made by Casper's? When I got mine it seemed like one of the wires was in wrong"

Hey I got mine from Caspers and the instructions did not compare to the instructions on the board. However, I did figure it out and passed the info on to John H and we both have had success. If for some reason John cannot help you let me know whereas I will look at mine. I am afraid to tell you how I think it goes off the top of my head without looking.

Jason
 

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fencekey said:
I may take you up on the O2 fooler help John. Is your's made by Casper's? When I got mine it seemed like one of the wires was in wrong, so I pulled it out and repositioned it . Perhaps that was my problem. I thought you posted in another thread awhile back that you never got a check engine light when you put your downpipe on? People were surmising that perhaps in 1996 the rear 02 stuff was not yet working on the OBDII ECU.
You're correct in that I never got a check engine light. I recently tried to get emissions tested and failed the cat and rear o2 sensor so I freaked out and bought the Caspers the same day. [They passed last year]. I wired it up correctly thanks to Jason and I still failed the cat and o2 sensor on the emissions tester!! I believe the problem resides in that I had the car disconnected from the battery for a LONG time and I hadn't driven it long enough (less than 100 miles) to re-instate the "drive cycles" when I got it tested. So I probably didn't need the fooler in the first place. Except for the lights, my '96 is the best yr I think. :)

John H
 

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HYPER-TT said:
Does the unit from HKS only work on 6 Speed cars? That is what their web site claims. I have a 93 Auto (OBD1) can i do this with no problems at all?

Mike
I've read that if you disable it on an auto, you will fry the transmission because it's supposed to close in between shifts.

As far as an O2 simulator, if you can't make the Casper's work, I made my own from a schematic either off of here or mkiv.com. Can't remember which.

About the spring in the trac TPS, I was going to cut it, but I just used a small flathead screwdriver to push it off of the rotating piece. I used epoxy to fill the holes in the throttle body. The HKS kit would have been nice, but the epoxy cost considerable less.
 
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