On 12/98, while still under warranty at 38,000 mi., code PO39 set as per your 'service bulletin number: 98876517'. I took the vehicle to a Cadillac repair center where they replaced the original PCM prom chip with an eprom 3.670 #16266767. It was my understanding that the new chip did not 'fix' the problem but allowed the onboard computer to ignore it, and not set the code PO39. Now, 17,000 mi. Later and out of warrenty a code PO56 is setting. This is the 'tranaxle input speed sensor' a $10 item that requires removal of the transmission for repair! it might be interesting to find out how many Cadillac that required the work outlined in 'service bulletin number: 98876517' eventually (after warranty coverage ended) required transmission removal and repair for a failed 'transaxle input speed sensor'

- Gig Harbor, WA, USA