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Ask Ron Z. Your Own Question
Ron Z.
Ron Z., - Toyota Tech -
Category: Toyota
Satisfied Customers: 17946
Experience:  18+yrs experience. State Inspector and Toyota Diagnostics
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My check engine light Trac off light and my vsc light all

Customer Question

My check engine light Trac off light and my vsc light all just came on. What does that mean
JA: Tell me a bit more about what's going on so he can help you best.
Customer: I am driving on a trip and while going up a hill these lights came on. I'm not sure what o should do
JA: Are you hoping to fix this yourself?
Customer: I want to know if it's safe enough to drive another 4 hrs
JA: Is there anything else the Toyota Mechanic should be aware of about your Toyota?
Customer: I haven't had any other issues
JA: I'm sending you to a secure page on JustAnswer so you can place the $5 fully refundable deposit now. While you're filling out that form, I'll tell the Toyota Mechanic about your situation and connect you two.
Submitted: 8 months ago.
Category: Toyota
Expert:  Ron Z. replied 8 months ago.

When the Check Engine light comes on, the VSC and Trac lights are also set, which turns these systems off. This is a self-preservation mechanism, in case the reason the Check Engine Light is on can harm or effect the VSC or Trac systems. So- fix the reason why the Engine Light is on, and the VSC and Trac systems will come back online.

When the Check Engine light comes on, this is the on-board computer's way of telling you it sees a problem in one of the monitored systems. Unfortunately, there are literally 100's of parts and sensors monitored in various systems, and to take a "guess" as to which part/sensor in which system is faulty, is virtually impossible. However, if you are not experiencing any drivability issues such as skipping, stalling, shifting problems, etc, then more than likely, the problem is going to lie in the EVAP (emissions control/recovery) system. Very commonly, this could be a faulty, loose or missing fuel cap or even putting fuel in while the vehicle is running can set the light. Check the underside of the fuel cap for any cracks or signs of defects that may keep the cap from sealing correctly. If there are any doubts about the inspection of the cap, replace it. Keep in mind, you will need a cap that meets OE Specs. Those "universal" or "locking" fuel caps sold at after market parts stores do not meet OE specs, and will not seal the system correctly. Check the top of the fuel filler neck for any signs of damage or debris. Check under the vehicle, around the rear areas of the vehicle, looking for any vacuum lines that have dry-rot cracks, holes or loose/missing connections. If these all check out, then the best thing to do at this point is to have the Diagnostic Trouble Codes (aka "p-codes") read from the on-board computer. These p-codes are what is used as a "starting point" for the diagnosis and will tell which part/sensor, in which system, has the fault. There isn't a Mechanic on the planet that can tell you what is wrong with the vehicle just by "looking" at the Engine Light. Every single Mechanic's first course of action WILL be to obtain the p-codes. It's standard diagnostic procedure. Once you get these p-codes you can more accurately and efficiently diagnose the problem and then make the correct repair. You can have these p-codes read FREE (except in California) at any local "big chain" part store (ie. AutoZone, PepBoys, Advanced, etc). As long as there are no drivabilty issues or shifting issues, then it is perfectly safe to drive the vehcile. You should however, have the codes retrieved at least to verify. If the problem does lie in the EVAP system, it is strictly for emissions control/recovery and will in no way effect engine performance in any way. If the problem lies outside the EVAP system, it may be a good idea to have it serviced as soon as possible, as prolonged driving with a problem with the engine or transmission can make matters worse.

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Expert:  Ron Z. replied 8 months ago.

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