I recently bought a 91 accord, with 95,000 miles from an old lady. Car was running great until the last two months. My car started violently downshifting while I was cruising at about 45 mph. It continuously shifts up and down while I'm pressing the gas pedal. I checked the error codes on the tcu and got 1, 2, 7, 8 (solenoids) and 15. I swapped the solenoids and now I'm only left with number 15, which is the kickdown shift shorted. I spoke to my mechanic and he suggested I changed the tps, so I bought a new one and put it on but when the tps is plugged in, the car either gets stuck in second gear or up and down shifts on its own. The only time the car doesn't have any problems shifting is when the tps is unplugged. I've tried everything I could think of (including changing the TCU) and my mechanic is scratching his head as much as I am. Anyone have ideas?

 

What is the resistance on the mainshaft speed sensor?