jdog0411

I've searched the forums but haven't found an exact answer to this issue/question, so here goes:

I've owned my 1990 LS400 for a little over a month, and have been driving it around with the "TRAC CONTROL OFF" light illuminated. This light is on when I start the car and stays on while driving. I never thought much about it because I figured that pushing the "TRAC OFF" button would turn it on (thinking the button had the dual purpose of turning it on if it was off, and turning it off it was on). I also assumed that the default setting was "off".

On a whim today, I pushed the TRAC OFF button and nothing happened. The TRAC CONTROL OFF light stayed illuminated. After reading the manual, I learned that the traction control should default to "on" every time the car is started and it stays on unless the button is pressed to turn it off. So.....why isn't mine on and why does my trac off button appear to do nothing? Is there a procedure I need to follow to turn the traction control on? Do I need to hold the button down for a period of time, or ? I'm assuming this isn't normal and I need some clarification on this before I start trying to troubleshoot a potential problem with the system.

twofanman

First step should be to pull the trouble code(s) for your TRAC system - stored in the ABS ECU. Here is a tutorial on how to accomplish pulling the code(s).

jdog0411

Ok, didn't think there would be any codes since I don't have a CEL light. I'll pull codes and see if there are any.

fencera

No procedure, just touch the button and it should go on/off.

Do what was posted above... also, when was the last time your brake fluid was flushed/changed? That can often clear up any issues with the system. See above site for tutorial.

Good luck.

jdog0411

I have no idea when the brake fluid was flushed, I've only had the car for a short time. It has had impeccable maintenance based on the Lexus service records, but I will probably need to have the system flushed since I don't have records for that. I'm going out in a few minutes to pull codes so I'll update with what I find.

deanshark

The brake system and the traction control system work together but I think if there's a problem the "trac" light will come on (it does for low fluid) NOT the "trac off" light. Just to clear, when testing for codes you would use the "trac" light. Does your traction control work? (try spinning the tires) I ask b/c one time my trac off light was on but the trac control still worked. The light went out on it's own after a while.

jdog0411

Well it turns out I don't think I have a problem with the traction control. I have a check engine light on now. When the CEL comes on, the TRAC OFF light also goes on. I am diagnosing the CEL now. I relplaced my two upsteam O2 sensors, but the CEL came back on. I am replacing the Engine Coolant Temperature sensor next and see how that goes.

curepunx

iTrader: (3)

IMO...

You should pull the codes from the CEL first before going about replacing parts or sensors. The code will lead you to the source of the problem.

Cheers

jdog0411

I did.

I pulled codes and had codes 25 and 26. After searching the forum it seemed the most likely culprit was the O2 sensors. I replaced them (the sensors looked to be original to the car), but am still getting the CEL. I pickd up the Coolant Temp sensor, so I'm going to go ahead and replace that. If I still have issues I'm not sure where to go next...possibly the ECU? We shall see...

curepunx

iTrader: (3)

After installing the new O2 sensors, did you reset the ECU by removing the EFI fuse or d/c the battery ground cable for a minute or so?

Also, are you having any issues with fuel mileage?

Maybe this link will help with the diagnosis:
https://www.clublexus.com/forums/ls4...-help-fsm.html

jdog0411

Yes, after installing the new sensors, I did pull the fuse and reset the computer. When I started the car afterwards, the CEL was not lit. It lit again after driving on the highway for a few miles and remained on.

It's hard to tell if I am having mileage issues, I think the mileage has gone down some recently, but I haven't owned the car long enough to know what I "should" be getting. On this current tank I'm at about 230 miles on a half tank, mostly city driving. That doesn't sound too bad comparatively speaking. I just completed the installation of the new Engine Coolant Temperature sensor, and took it for a test drive (I also cleared the codes again before starting up). The car ran very well, and no CEL this time after about 30 minutes of mixed city and highway driving. I'm hoping maybe the issue is resolved. Guess I will find out after more test driving tomorrow.

jdog0411

The CEL came back on....*&$^%! Not sure what to do now, I'm still getting codes 25 and 26.

curepunx

iTrader: (3)

Maybe you should get a second opinion from a local trusted mechanic on the O2 sensors. Maybe the wiring isn't sending proper signal?

jdog0411

I think that's the point I'm at now....I think either the wiring is faulty, there is an issue with the Computer, or something along those lines. I'm going to have to take it in I think since I don't want to mess with it anymore. At least not until it gets warmer...tired of freezing my a$$ off in the garage working on this thing.

jdog0411

I took it to a mechanic and they said they tested the sensors and they were not reading anything, so they still thought the sensors were the problem. They said they don't see too many of the universal sensors that actually work. They wanted to replace them with OEM sensors because they can't diagnose any other issues until they have known good sensors installed. They quoted me almost $800 parts and labor to replace the two sensors.

I told them no thank you and picked up the car. I'm going to take the universal sensors off tomorrow and test them out myself. Maybe I screwed up the wire splices/connections. Then if they are indeed bad, I will order OEM sensors from Sewell and see if that rectifies the problem.