I erased the code and still have high RPM shift. Do you have suggestions to fix communication error/code? Is there a related sensor that I could try replacing? This car has taught me to be very patient in troubleshooting- I will pursue any solutions that are within my abilities. Thank you in advance.

There is no slip in the transmission, but it is not shifting at normal RPM range. It will shift around 5,000 RPM or not until I release the accelerator. Check engine light shows P1618. Fluid is at proper level and in good condition. Please help.