My trac light is on most of the time. No check engine light, just that light and the car idles weird if the A/C is not on. How can I find out what the light means?

 

It is a 95 SC400

 

the "trac off" light on the bottom left, or the traction light in the tachometer?
First thing I would check is whether or not the check engine light comes on when you switch the key to the "on" position (without starting). It'll be the second to left light. If this light doesn't come on, your CEL bulb is likely bad, and you have an o2 sensor issue.
if the cel light does come on, there might be a problem with your traction control ecu, wiring, or possibly an unplugged traction control plug on the throttle body.

 

Its the Trac light in the tachometer. The check engine light bulb is working, but the light never comes on. So if the check engine light doesnt come on with the trac light, it would be something with the traction control only?

 

Hey I have been having the IDENTICAL problem. Same make LEXUS, model SC400, and year 1995. TRAC light is on. Multiple mechanics cannot diagnose. Also, car idles low when AC is off, and idles high when AC is on. Have researched and found various hints people have contributed from the site:

#1 There is an accumulator next to the master cylinder ,should be some yellow tape on it cautioning about contents under high pressure, use a small piece of vacuum hose on the bleeder nipple to avoid brake fluid squirting all over your engine compartment, with engine running bleed all the air from system , the trac light should go out. I followed these instructions from my buddy at Cherry Hill Lexus and the light does not come back on. They also stated the high pressure hose that runs beside the accumulator gets soft and clogs up the unit.

#1.2 to add to that, go to www.lexls.com look up diagnosis, there they will show you how to diagnose the car, i have the same trac light problem, the problem according to the diagnostics is a constant running of the motor because the accumulator keeps loosing pressure. there is no leaking break fluid, so i believe i just need a new accumulator. Please dont go to the dealership, im buying mine on ebay and installing myself hopefully, just as soon as my VIP grill and window tint come in, so in other words if your not leaking break fluid just press the trac off button when you get in until its fixed.

#2 Most likely it is TPS.
1. Check the code
2. Replace the TPS - http://www.lexls.com/tps.html
I had a same problem. I checked the code and it was a bad TPS.
Replaced the TPS and the problem was fixed.

#3 On each wheel hub assembly there should be a magnetic pick up sensor(wheel speed sensor), check and see if there are any partially torn wires(should be 2 wires each sensor), or loose continuity. I believe these are for the ABS, but they are also utilized in TRAC control.

#4 mine did the same thing, ended up being brake fluid too low

If anyone has a DIRECT answer, or solution, would be greatly appreciated!

 

The high pressure hose solved my problem.

 

So I am still working on trying to solve this issue in my '95 SC400...

Have replaced ABS/TRAC ECU (light is still on)
Have replaced Sub-throttle Position sensor (light is still on)
Have replaced high pressure hose (light is still on)
Bled the actuator, fluid came out, no air (light is still on)
Attempted to bleed the accumulator, no fluid came out, even when jacking the car up and pushing the throttle with engine running, still no fluid came out (light is still on)

Any ideas?? Thanks in advance!

 

Check your ABS sensors. When I replaced the rear k member I broke the bolt that holds on one of the sensors. I've had a trac light on ever since.

 

Thanks for the suggestion. Will get it on the hoist and update the thread.

Part of me is leaning to the accumulator since no brake fluid would come out of it when bleeding it, even when jacking the car up and pressing the throttle to spin the rear wheels..