Cadillac Repair: 91 caddilac deville 4.9L electrical problems, electrical schematics, aftermarket radio

Question
well i just bought a 91 deville and the only problem is that the fuel in tank just says"c" as well as the ECC reading but it worked every once in a while and i got the error codes of E-47 and E-52, the heater will not turn off and it makes a high pitch hissing noise threw the front speakers when i press on the gas or when the bass hits hard. i think its proly a ground that got messed up when the after market stereo got in stalled but i am open to suggestions that dont require alot of money and not too much time but i can handdle a 2 day job. thank you

Answer
What you have is the ever common fault of someone who is inexperienced in installing an aftermarket radio in a Cadillac of which is very common to attach the wires incorrectly and frying out of electronic components within the computer system.

You will need a set of electrical schematics in order to properly install the radio which is most likely internally damaged because whoever installed it wired it incorrectly.

You will need to e-mail me at: onlineautohelp@msn.com