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Are these the only two codes in the system?
These problems are normally caused by wear of internal components inside the transmission. Replacing these worn parts is the fix for these issues. I have included a technical service bulletin that outlines the nature of the problem for you.
Please let me know if you need additional information.
Bulletin No.: 04-07-30-034A
Date: October 13, 2009
Subject: Service Engine Soon (SES) Light On, Diagnostic Trouble Code (DTC) P0741, Torque Converter Clutch (TCC) Excessive Slip, Transaxle Chuggle, Slip/Surge (Inspect and/or Replace Various Internal Transaxle Components)
Models: 1998-2002 Cadillac Eldorado1998-2004 Cadillac Seville1999-2004 Cadillac DeVille2000-2003 Oldsmobile AuroraEquipped With 4T80-E Automatic Transaxle RPO MH1
Supercede:This Bulletin is being revised to update the Parts Information. Please discard Corporate Bulletin Number 04-07-30-034 ( Section - 07 Transmission/Transaxle)
Some customers may comment on the SES light being illuminated and a chuggle or surge being felt when driving at higher speeds.
Technicians may observe on the Tech 2(R), an excessive torque converter clutch (TCC) slip speed and DTC P0741 set as Current or in History.
The P1860 code indicates a short or open in the torque converter clutch solenoid control circuit.
You have two separate problems. The P0741 code must set first because it will not set with the P1860 code present.
You likely have the mechanical failure listed in the bulletin and a bad torque converter clutch solenoid.
The P1860 code can be fixed by replacing the TCC solenoid, this requires removal of the side cover of the transmission. This is still a major job because the side cover must come off. This requires removal of the front suspension cradle.
The P0741 code will require removal and disassembly of the transmission. This is a huge job that requires some specialized tools and equipment.