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Ron Z.
Ron Z., - Toyota Tech -
Category: Toyota
Satisfied Customers: 17972
Experience:  18+yrs experience. State Inspector and Toyota Diagnostics
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VSC trac light and check engine light just came on, stays

Customer Question

VSC trac light and check engine light just came on
JA: Does the light stay on, or does it blink?
Customer: stays on
JA: What is the model/year of your Toyota?
Customer: 2004 Toyota RAV4
JA: Are you hoping to fix this yourself? What have you tried so far?
Customer: I tried redoing the gas cap again but it did not work
JA: Anything else you think the mechanic should know?
Customer: no
Submitted: 3 months ago.
Category: Toyota
Expert:  Ron Z. replied 3 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).

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Expert:  Ron Z. replied 3 months ago.

Hi! I noticed this thread was still open and you did not leave a rating , so I wanted to check in and see how you made out? Did you have those p-codes scanned? Were there any other questions you had on this? Was there any other information I can provide to better assist? If you have no further questions and simply forgot to leave a rating, please take a second and use the stars at the top of the page to rate our Q&A session. Thank-you!

Expert:  Ron Z. replied 3 months ago.

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