1995 cad devil p039 diagram procedures

If it is a 4.9 powered Deville, you have a 4T60e transmission, the 4T80e was exclusive to the Northstar powertrain. In either aspect, I don't believe there is an updated prom, at least I never heard of one. It may end up as leakage in the hydraulic circuit internal to the transmission, a faulty converter, it could also just be a faulty brake/tcc switch. The procedure is rather lengthy, and references 4 charts based on the result of initial diagnosis. I will include the preliminary test chart, see if you can determine which chart applies based on your findings.

CIRCUIT DESCRIPTION
This diagnostic test monitors engine rpm and vehicle speed and compares them. The Powertrain Control Module (PCM) will set Diagnostic Trouble Code (DTC) PO39 when engine speed exceeds the fault value for a particular vehicle speed. This code can set due to an electrical problem or slippage of the Torque Converter Clutch (TCC) or transaxle clutches. If a TCC or transaxle clutch failure has occurred, the failure is more likely to be observed under high road load (high Manifold Absolute Pressure (MAP) ) conditions. Use code snapshot data to confirm.

TEST CONDITIONS

Codes P026, P027, P031, P032, and P034 not set.
PCM commanding fourth gear.
Engine RPM 3100 or less.
Engine in "Closed Loop."
MAP between 29 kPa and 80 kPa.
TCC commanded "ON" and brake "OFF."
TCC mod solenoid at 100% duty cycle.
Throttle position switch open.
TCC Applied Test Table

FAILURE CONDITIONS
DTC PO39 sets when the engine rpm is greater than rpm fault as indicated by the "TCC Applied Test Table, " found in the above image, for more than 5 seconds.

ACTION TAKEN

The PCM turns "ON" the "Service Engine Soon" Malfunction Indicator Lamp (MIL), and remains "ON" for the ignition cycle.
The TCC is disabled for the ignition cycle.
NOTES ON FAULT TREE

The "Transaxle Electrical Operation Chart, " found in the accompanying image, checks the electrical operation of the transaxle using the transmission test box J38791. This chart then references Charts "A" - "D, " in this article, for specific checks.