I Have A 97 Isuzu Trooper With A 4L30-E Trans That Stays In 1st Gear Only. Reverse Works Fine And Fluid Level Is Correct. Could It Be The 1-2,3-4 Shift Solenoid and if so where are they located in the trans? All The Lights In The Shift Indicator Work Any Suggestions? There are no codes either. Also Low gear works fine. I've so far changed the Trans filter, fluid and Throttle position sensor and still no change.