Quote Originally Posted by DanGTP View Post
You can't trust that method with newer cars. Some have built in safety measures that will kill the car if the battery is unhooked. Also, you chance maiming your PCM.

OP, go have your charging system checked. Usually a light like that is a sign of a failing or failed alternator. It's also possible that you simply have a loose wire somewhere in the charging system.
Im not talking about most cars im talking about his gp...ive done it hundreds of times.it would just be like if the battery when completely dead what would the diff be plz inform me...and if it did your telling me it would fry the comp??i doubt it...I didnt say disconnect the terminal and throw it around the engine bay....or ground it out on somthing..all you do is loosen it and quikly lift it off and if it starts to die press it back on. if it does start to die its your alt if it stays running its your battery then you get which ever it is tested just to double check. its an old mechanics trick.....i guess you learn somthing new everyday bc i didnt know there was any sensor incase the battery was disconnected guess its on the same car with the battery fluid light idk lol....i know a lot of things are electronicly controlled on the newer cars but this trick does work and will help if done properly...im not saying its the best way to do it a meter or tester is always better but doing this trick WILL point you in the direction needed to start diagnostics.....Ive had the main positive wire on my 2001 truck short out on the body meaning it was routed through the body panel and from vibration cut itself totally groundint out and didnt fry a single sensor or anything so i doubt doing what i said will hurt anything...and again im not saying to throw it around the engine bay....good luck guys....

If you cant manage to do this on your car/truck then u def shouldnt even open the hood..... no offense to the op...