Cadillac Repair: climate & fuel data display, cadillac sedan deville, wire terminals

Question
How can I get rid of the c on my fuel data and climate contol display? I read a previous answer & there is a ref. to tsb t90-318. What does this entail. I ve reset the system but it still shows the c & nothing else. If capacitors need to be installed thats no problem but to where? Any help would be greatly appreciated. Its been a great car. 89 cadillac sedan deville.  
Thank you
Ed  

Answer
Hi Ed, That service bulletin describes repairs if the pannel lights flicker or if the settings change by themselves then a capacitor will help stop that but it doesn't mention anything about c or d on the display. Here's what you need to do for that...Unplug the programmer electrical connector with the key off and then turn the key on. If the displays are normal replace the programmer...Still shows c turn the key off unplug the cliamate control panel key on. If normal replace the panel...Still shows c key off then plug in the cliamate panel and unplug the fuel data panel key on. If normal replace the panel if still show c then key off and with all panels, programmer and body computor unplugged test for an open or short to ground on ct713 which is a yellow wire terminals U,V,W at the ECC, terminal C at the FDP , terminal B2 at the BCM, and terminal V at the programmer. If the wireing is good and the terminals aren't spread then it looks like the body computor will need to be replaced to get the displays to read correctly. Hope that helps. Bill