AutoZone offers FREE code checks here in Texas. They came out to my 2000 Rodeo in the parking lot, hooked up there code checker and told me the two codes that were causing my CEL to come on. When I asked the person how do you find out what the codes mean, she invited me back into the store and looked up the codes on her computer, then wrote down the ino on a piece of paper. I didn't even buy anything from them. That's good service and I will be back when I nee dto make a parts purchase.