I moved the shift selector to 3 while traveling up a long grade at approximately 60mph. Not long after the flashing up arrow and check engine light appeared. The only code is p1618. I have removed and cleaned the transmission speed sensors and connectors, resoldered the ABS module and cleaned its connectors, and ensured the ECM and TCM are seated properly. The harness appears fine.
I guess I'll have to shell out $90 for a VIDA scan and have the ECM and TCM contacts cleaned and examined. Anyone with VIDA local to Asheville, NC want to make $50 scanning my car?
What else could be at fault?