2004 Volvo s40 T5 185,000 miles with an automatic transmission. The car has sat for a couple years, I bought it from someone whos daughter had a fender bender with it sat ever since so I bought it and fixed it up. For some reason it ran rough but it had no check engine light on so I excused it as bad gas from sitting. I test drove it and the transmission malfunction notice came on and the car went into limp mode. I parked it for a while and took it back out and the check engine light was now on but it went down the road fine and there was no transmission issues. It shifted very smooth. I got it home and now it had a high idle but it wasn't running rough. I pulled the codes off of it and it had P0600, P1719, P0725, U0103, P0863. Wow a lot of codes, they are all related to the transmission and the ECM and Transmission control module/transmission itself. I haven't gotten into diagnosing it yet, just thought I would see what some of the experts think since this is a lot on my plate. Sounds to me more of some sort of electrical/module control problem, since the transmission still shifts good and doesn't slip so I don't think its an internal mechanical failure. The car did sit for a couple years so anything is possible. I did see some evidence of possible mouse or animal nest in the engine bay on top of the transmission. Haven't gone too far into yet though. Anyone have any thoughts? (I'm certain the issue is not accident related, it only took out the front bumper very light accident.)

 

With nearly any Volvo of that vintage / mileage, you really do want to do a transmission fluid drain-and-fill. That won't replace all the fluid, but it may well restore the condition of the fluid to the point where sticky valves and/or solenoids start working right again. Worst case, you will have just done some very necessary maintenance, even if it doesn't fix the problem. Also, I'd suggest resetting the codes and see if they come back - some cars have codes from long, long ago - or that were created by a low-voltage "event" (like a bad battery / alternator), and my not really indicate a problem.

FWIW, if your S40 is like my '05 V50, the tranny dipstick is impossible to get to - you'll want to read up on the drain-and-fill procedure, and make SURE to get the right fluid (might be different for yours than mine, so I won't make any suggestions there).

 

clear all the codes, pull out the TCM and clean all the contacts then see what codes reset.

 

I cleared the codes while the car was running and the idle immediately dropped and the car went back to normal idle but was running rough. I'll keep you posted as I continue to drive it.