Check Ingine light is on. Code is P773

Question

Research shows possible causes... low or dirty transmission fluid.

What is the chance of that or something more serious?

Answer 1

P0773 Shift solenoid E electrical malfunction

Think of the ECM as a scan tool itself, one of its job is to look for open circuits, short circuit, grounded circuit rationality, What the ECM is see the lock up solenoid as off. Chances of other problem , if there is a gear ratio set with this, or the transmission slips or flares, which does not have to set a code condition, the reason open circuits, short circuit, and grounded circuit set first.everything else (beside a catalytic damaging  condition) is suspended, So test drive is essential