... Went to the PA Mountains and got the "check engine light" in the yellow color... Good that I have had my diagnostic tool with me: "Innova 3030" - not pricey at all but very helpful, so I figured out that my lower "downstream" oxygen sensor gone! These readers can be used on any! Trucks or cars from 1995 till today made - ANYWHERE!!! at any place around the World. To make long story short: the code reader is getting connected to your computer afterwards and gives you precisely the code and the part number you need, so that you can come to the mechanic with your part and ask him to replace the old one! He will be asking questions such as: "How do you know, and who told you and so one,..." you will win!~ That is the most important part - you safe BIG!!! To come to mechanic with the "check engine light" and to run diagnostics and to let him to get you the part and to replace it - $350.00 dollars and for me to bring the part to him and for him to replace it - $75.00 dollars That is some saving.... Think you might need one??? :-)