Hi Pearl, I'm Gary. Have a 1999 Eldorado. The dash lit up about the battery not charging and the car shut down. I put a different battery in it and it started up so i drove it home and parked it. The next morning It started up. I drove it about 2 blocks and once again it shut down. I ran obd2 and code p0603 came up. I replaced the alternator
and the plug since it was looking pretty bad. Charged the battery over night. The battery started the car and tested at 12.2 V. As the car ran it came down to 11.8 volts in about 2 min. However no dash lights came on. I Shut the engine
off and out the obd2 back on. Now it shoes 2 Codes Th p0603 Plus p1638. ALSO the instrument cluster came on and now shows " Generator F Terminal circuit.. Also I tried a NEW Battery which does the same thing. .
JA: Lots of things can cause problems with the battery. The Cadillac Mechanic will know what to do. Are you hoping to fix this yourself?
JA: Great! What have you tried so far?
Customer: I just told you
JA: Is there anything else the Cadillac Mechanic should be aware of about your Cadillac?
Customer: Other than it's one of a few cars GM should have never built.
JA: OK. Got it. I'm sending you to a secure page on JustAnswer so you can place the $5 fully-refundable deposit now. While you're filling out that form, I'll tell the Cadillac Mechanic about your situation and then connect you two.