Toyota Repair: Toyota RAV4, toyota rav4, yr model

Question
Hi Ted, I am a retired lady, so these check engine lights that keep coming on are getting costly for me! Is there a way I can turn it out myself? It has been to repair 2x and it came on again after that and will not pass emissions in this state (ID.) which also cost $15 each. (I'm starting to think it is a computer plan!) Each time it fails I have to take it into dealer or repair, which has been very costly. Last time it had 2 codes.
Any help on this is appreciated. Otherwise, its a good car, no problems but this light! I am handy and could reset myself if I knew how.
Thanks, Happy Holidays

Answer
Some of the trouble codes can be cleared by disconnecting the battery negative terminal and reconnecting it after ten seconds but keep in mind that clearing the codes does just that, it turns the light off but the problem is still there, I may be able to help if you could let me know what the codes were the last time, depending on what year and how many miles and what the trouble codes are, the repair may actually be covered under the emission control warranty. If you decide to follow up please let me know what yr/model and the mileage and most importantly the trouble codes.