I have a 94' Sedan Deville, 4.9 with the computer controlled trans. am having shifting problems and want to access the trouble codes. according to chiltons book jumper wire from B to A terminal should allow the computer to flash the "service engine soon" light. Information center displays "timing mode" How can I retrieve the codes without spending 500.00 on a reader. I LOVE this car, 236,000 and still runs fabulous.