I would check the fluid level first, this guide can help:
If the fluid level is okay it looks like the transmission is having a problem internally, either it is coming apart and clogged the filter or the front fluid pressure pump is weak.
Here are the code definitions:
Code 66 - Transmission Fluid Pressure Low
It could be caused by a failing transmission pump, a clogged transmission filter, or issues with the transmission fluid level.
Code 67 - Transmission Fluid Pressure High
This code indicates a high transmission fluid pressure condition.
Code 81 - 1-2 Shift Solenoid Valve Performance (4L60-E Transmission)
Code 82 - 2-3 Shift Solenoid Valve Performance (4L60-E Transmission)
Let us know how it goes. Please let us know if you need anything else to get the problem fixed.
Monday, September 18th, 2023 AT 1:56 PM