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VSC and TRAC OFF light

I have at 2005 Toyota Highland with 175,000 miles. The VSC, TRAC OFF and CHECK engine light came on. Toyota dealership wanted $85 to run the diagnostics. Local repair shop ran diagnostics for free…said I had a small emission leak…we replaced the gas cap and the shop turned off the lights. Drove about 400 miles and the lights came back on (put gas in the car around 350 miles). Any thoughts I what I should do? Does the dealer run a different computer diagnostics check than would the local garage? Could these lights come on if it is just an emission leak, or is there something wrong with the vehicle stability control and/or traction control? Thanks for your thoughts.

To be honest, you can’t expect a free diagnosis to be very accurate. In all likelihood, the check engine light is on for the same reason it was on in the first place. In other words, a flat out incorrect and/or incomplete diagnosis

That is why many of us professionals cringe at the thought of free diagnosis. You get what you pay for

That dealership might have applied the diagnosis fee towards the cost of repairs, had you opted to go with them. I don’t know if dealerships do that, but some independent shops work like that

I suggest you PAY for a diagnosis this time, perhaps from a different shop, or perhaps even that dealer. One thing in the dealer’s favor. He has easy access to all of the Toyota service information, which might prove useful in this instance. It sounds like you had some kind of evap codes, and Toyota has published several service bulletins, in regards to correctly diagnosing and repairing these particular problems. A good independent shop will also be able to access this information, though, but it’s not necessarily a sure thing, depending on what kind of repairs this shop usually does


If for any reason the Check Engine light comes on, the VSC, Trac Off lights will also come on.

The reason is, VSC and Trac systems use the engine to control the vehicle. They also use the ABS.

So once it’s figured out what’s causing Check Engine light to come on and it’s repaired so the Check Light shuts off, the VSC and TracOff lights will also shut off.


Just because it happened to my 2005 Lexus, check the condition of the battery. Mine was on its last legs. A new battery and everything went back to normal.

When I drove my Mexican car to the border, last October, in the happy state of Tamaulipas, a very dangerous place, those lights came on, and scared me pretty bad.

At the time, someone told me that engine misfire could cause that, among other things. It has not done it again.

My personal theory was that the harsh vibrations of the unbalanced tires could have induced an intermittent of some type. A theory no one seems to ever mention, though in August we read plenty of proof that current business models make it nearly impossible to diagnose intermittents. I drove very slowly the rest of the way to the border, and the lights did not come on again.

So, what tester says agreed with what I was told at the time, as far as those lights coming on for any check engine light, not the intermittent theory part.

Looks like a job for a freeze frame or live data scanner??? If any check engine light causes those two lights to come on, one must find out what the true failure is. If I misunderstand and only some failures cause those light failures, please correct me.

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If it was free there wasn’t any kind of diagnostic check. Someone simply read a fault code, looked at some database of “fixes by professionals” and decided that the simplest, easiest, cheapest thing to do was to replace the gas cap.

A professional level bi-directional scan tool, a smoke-generating machine, a system wiring diagram, a competent mechanic, and some time are needed to properly and completely diagnose the problem. You’re not going to get that for free. Would you trust a dental exam from a dentist that didn’t charge you for her time, equipment, or expertise?

Modern-day Toyotas turn disable Vehicle Stability Control and Traction Control (and turn on the warning lights) whenever an engine fault is detected. Fixing your check engine light will turn off the other lights.


The error code that says replace gas cap could also mean a bad charcoal canister.

And for some reason some aftermarket gas caps are not that good. Try replacing the gas cap with an OEM gas cap.


Oops, you mentioned “engine fault” which I agree with. I was intending to respond to this one from Tester-

If for any reason the Check Engine light comes on, the VSC, Trac Off lights will also come on.

It seems ridiculous to me that a manufacturer would disable traction control for an evaporative emission fault. What is the possible thinking here? In what way could a fault like that be reason to disable a safety feature?

Irlandes- I tried sending you a message but for some reason the site would not let me type in the box. If you have a serious misfire, your check engine light will flash. It is trying to get you to shut off the engine to prevent damage. If your trac/vsc lights come on all it means is you car will behave as if it did not have those systems.

Read and learn.


If this is accurate, I learned they are morons-

This is a self-preservation mechanism, in case the reason the Check Engine Light is on can harm or effect the VSC/Trac systems.

They are in control reading the various sensors and determining when to illuminate the check engine light. Therefore, they can easily tell if it is something that would NEVER affect the traction systems- like an evaporative emission fault…

Well, no, not really. I’m sure Toyota engineers would love not to turn on the check engine light just because of a perceived small fuel vapor leak. But the engine light is required to be on in the event of a failed emissions monitor indicating the malfunction of a part or system that can cause the tailpipe or evaporative emissions to rise above 1.5 times the federal test limits. Because Uncle Sam says so.

I do agree that there are valid reasons not to disable VSC or TRAC because of an EVAP fault, but perhaps the VSC and TRAC systems aren’t smart enough to know exactly what’s going on in the engine room, so they err on the side of caution.


Turning on the light as required by law is completely separate from ACTIONING other systems based on it. I never said they shouldn’t turn on the light. All of these subsystems communicate with each other over a network (e.g. CAN bus). Each and every one of them has a microcontroller that is processing data signals, commanding outputs and receiving/sending commands/responses between the various subsystems. To not utilize those resources to the full extent by intelligently determining which conditions warrant disabling safety features is ridiculous IMO.