I picked up a 2001 S 40 1.9 liter turbo.
I've been working on this car for over a year and a half and it runs great. It's got 170,000 miles on it. And I can drive it for months and get no lights, error lights, except the light bulb out light . and the traction control bulb that's an idiot like on the dashboard. As I've said, I can drive her for months on end. Nice and slow, nice and easy. Got nowhere to go on all day to get there. But When my wife drives it to work, which is 10 miles and back 10 miles, she tells me to check engine light comes on. Almost every time she drives it, the check engine light comes on. It befuddles my mind I asked her, what is she doing wrong? She says nothing. I. Have a brand new 2022. Ford escape hybrid? She drives that? I'm wondering what she's doing to that. I'm trying to keep the mileage low on that. So I got the Volvo for her to drive But when she drives at the check engine light, complain, what the hell. What the hell is going on here? any ideas? I'm desperate.

 

What codes are stored?

 

different all the time P0700 P0500

 

The 0700 is a TCM communications error code and the 0500 is a speed sensor sensor so it sounds like they are related. What I'd do is disconnect the battery, pull out the TCM, clean all the terminals on the connectors and TCM pins with electronics cleaner then reinstall/clear codes and see what returns.