Hi XXXXXXX,
That engine light coming on is our ONLY clue at this point, because it set a code in the computer system that we need to get out. A scan tool or code reader will be needed to do this. Most parts stores will read the codes for FREE for you. There are literally hundreds of possible codes that can set, that's why it's so important.
Thanks for your question,
Ron
The light I refered to was the same as you did, there are codes stored in the computer right now that can direct us what to do next. It's all guess work without the codes. The transmission shifting is controlled by the computer system.
Thanks again,
ASE Certified Technician
33 years experience in driveability for domestics and imports, also a professional Instructor
Yes, there are shift solenoids inside the transmission.