I have three lights constantly on, they are, the service engine soon light, tire pressure light, and air bag light. I have recently purchased car. Was told that the tire pressure light was on because of a censor needing a battery, he said it was 145 dollars so he did not bother with fixing. The air bag light, he said was on because, the steering wheel was replaced with a removable one and the air bag was in the original steering wheel. I replaced the steering wheel with the original he had, hooked the air bag electronics and horn, but light still on. Woe is me! The service engine light was not on when purchase, it after driving it home 1 hour! It came on during this trip. All I did was fill the tank, but made sure the cap was reinstalled with the three clicks. I do not know what prompted it to come on. I purchased an Ancel JB 700 code reader analyze, to try to read why these lights were on and how to turn them off, the code reader did nothing about or tell me about these lights. It would not reset the check engine light or anything, I boxed it up and this worthless thing is going back. It did tell me a code I think PO420, that said something like the cat converters number one bank ya di ya di was ya di ya di. When I looked up the code it said nearly 12 things could be wrong. So this is where i am at, I bought the code reader thinking it would tell me what to do, because I have an inspection coming up for the new used car, and I am not sure it will pass with these lights on.