My S70 non turbo Base model has twice thrown the PO740 generic code. The only posts in archives are about AWD model. The first time my tranny fluid was 3/4 pint low and I topped it off. I have fathfully changed the trans fluid since I purchased car at 76,000 miles and it was previously dealer serviced. 20,000 miles on recent fluid change. AWD forums indicate torque converter switch. Advise please

One last thing. I promise! I recently replaced all tires with a new size of 205/60R15. These are not the recommended size but have a fine appearance and handle great. Shortly after replacing the 195's with the 205's the CEL appeared.

Those sizes are not a big deal and have nothing to do with it. Just so long as they do not rub the inner fender liner, enjoy the extra grip.

Klaus
--
The more I learn, the more I forget. So why learn?

The P0470 (TCC Circuit Malfunction ) is indeed the converter switch. But it seems to be purely electrical in nature. I would first check the wiring looking for chaffing or a poor connection.

Are you using synthetic or regular tranny fluid and which "flush" method do you use?

Klaus
--
The more I learn, the more I forget. So why learn?

Yes it was resistance in the terminals along with high resistance in the SL (lockup solenoid). Terminals cleaned and solenoid replaced. I was told this is very rare on the S70 and could only be from a possible wreck. The car has a rebuilt title and I have driven it for 76,000 miles. Thanks Dr. Klaus

I use the valvoline instant oil change commercial method? Thanks again.

Are those the guys that also change your oil? Stop doing that! Where in the heck are my wet noodles???? You need some lashing!

Change your own engine oil and use synthetic oil and a Mann filter. FCPGroton sells the filters for less than $40 for a case of 10, and have them also ship 10 crush washers.
Make your own tranny flush kit: 6 feet of 1/2in inside diameter tubing, 2 or 3 gallon plastic jugs, like milk or water, a long thin neck funnel, and a case of Dec/Mer or Mobile 1 ATF. It only takes 30 minutes to DIY.
The high pressure machines used to flush fluid are death to these fragile trannies.

No, I dont have a diagram for the 1997-98 trannies. Just follow any wires that go to the tranny and make sure the leads are not loose.

Klaus
--
The more I learn, the more I forget. So why learn?

I use Valvoline semi synthetic changed 17,000 miles ago. Can you provide the wiring route to follow or is it in the Haynes manuel? Thanks