I have always wanted one of these but always thought they cost hundreds of dollars.  As a woman I know that I am a target for any dishonest repair shop, and not knowing I am familiar with car mechanics they sometimes lie to me about what my car needs.So for that reason alone, I was delighted to get this small but powerful tool.  Now before I take my car in for maintenance I can scan its codes quickly and be prepared for the inevitable news that I need a lot more repairs on my car.  I can smile and drive off and leave them looking confused and puzzled when I don't take the bait.  Not to slam all repair shops but I have run into some heavy duty attempts at conning me into paying for repairs my car doesn't need.I carry this with me in my car, especially on car trips, for those scary times when I'm on the road and the check-engine light comes on.  I also keep the manual in my car so I can diagnose the code by the side of the road and decide if it's safe to keep driving.This just plugs in, and you push the button and read the codes, or lack of them.  It's simple and fast to use.  When I used to buy and sell used cars I could have used this.  The repair manual is complete with hundreds of codes and descriptions for whatever readout you get.  You will need to write down your code when you get it, and compare it with the manual to see what it is indicating.I love how this will also check the emissions control system, and the air conditioning system.On my 2012 Accura the plug is right there under and to the left of the steering wheel. It's not even in the dash or in a compartment, so it's simple to find it and plug this in.  You plug this in while the key is turned so the dash lights come on but the car is not running, to activate the cars electrical system.  This requires no batteries.To test how accurate this is, I dislodged the gas cap and tested my car with this.  Sure enough it gave me the code for a problem with the gas line.  I can promise you this works and is accurate based on my test of it.How they can sell this small computer at this price I have no idea, and the 40 page manual that comes with it is amazing, giving you hundreds of codes and which parts need replacing. I am thinking the price must be wrong here.I have taken back control and empowered myself when I go to a car repair shop with this.  It's my new secret weapon and I love it.I was supplied with a free sample which did not affect my review.  This is a great product at an amazing price.