Wouldn't shift to higher gears

Hello, I'm Danny.

Code P0700 is fore a code being set in the transmission control module. Code P0888 is a code set for the transmission control relay always being off. You will have a bit of wire testing to do so here is a tutorial showing how to test wiring and a tutorial on how to test a relay:

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

https://www.2carpros.com/articles/how-to-check-wiring

I've attached picture diagnostic steps below on what to test for these 2 particular codes on your car. Keep us updated as to what you find. Hope this helps and thanks for using 2CarPros.

Thank you for such a complete response! After paying for 2 shift solenoids and destroying an oil cooler line, my girlfriend's son asked me for help. I started researching myself and suspected the trans relay. I bought the relay for $23.00 and replaced. All problems resolved. Hundreds of dollars wasted by not troubleshooting properly. Hopefully he learned from this...

Hello Again.

You're welcome! I'm glad to hear you were able to fix the problem with the relay. Thanks again for using 2CarPros and we hope you will use our site again in in the future.

Danny-