Cadillac Repair: 1990 caddy deville, stereo amp, battery cables

Question
I just brought the car two weeks ago the service engine light  is on but the car rides GREAT ! I installed a radio amp and sub about a 2week ago. electronically the car started actin funny but it still started up This morning I tried to start the car and got nothing ITS TOTALLY DEAD!! please help is it the starter? alt and Batt is good tried to jump it I get nothing!  

Answer
Hi Kia,

     Since the service engine light is on that might be a good place to start. To check for codes the battery has to have enough charge to allow the dash to light up when the key is turned. Then press off and warmer buttons on the climate control for 5 seconds or until the fuel display goes into diagnostics. It will show 888, EE or E codes and then FF or F codes and then 7.0. Write them all down and then get back to me and I can tell you what may have caused the light to turn on.

      If the dash is blank with the key turned or the headlamps don't come on then you could have loose or dirty battery cables or a dead battery that needs the be charged or replaced. Try takeing the battery cables both off...make sure the black/negative cable is the first one you remove and the last one you install...and see if there is any greenish corrosion that needs to be removed with a small flatblade screwdriver or a wire brush. If ok then reinstall the cables and tighten them so the cables can't be turned. If you suspect the battery is over 4 years old get it replaced and that could allow the engine to start.

    Because you had the battery go dead after installing the stereo amp and sub one or both might have been wired so they stay on all the time. My brother and I were replaceing ball joints on his car and listening to his stereo and amp one time and much to our surprise after about 35 minuits the radio quit. Turns out the amp used so much battery power that the battery went very low and we had to listen to a radio that plugged into the wall and to charge his battery up before the engine would start.

     So what I would do is make sure the battery is good. Double check the amp and sub installation to make sure they are wired up correctly and turning off when the key is off. At that point the engine should start and run and you can have the alternator and starting system tested by your mechanic to make sure they are ok. There is a possability that the ignition key or lock cylinder wires are bad but try the other things first and let me know if you need more help.

    Happy Holidays, Bill