I have a 1997 Legacy L wagon. It has 170k miles and it is an automatic. I recently pulled the engine and replaced all the front and rear seals and the timing belt. I also had a transmission put in that I got at a junk yard. We got it all in and I took it out today and Im getting a check engine light for the TPS P0122. It drives fine but it seems to not have as much acceleration as it use too. When I was going up a hill today the speed limit was 55mph and I could only get it up to 50mph. When I push the gas to the floor Im not getting any torque. It just slowly goes up to speed. Could it have something to do with that TPS?

It was that TPS. I moved it around in a couple different positions and bingo... the light went off and all its power was back. That scared me. I thought for sure the timing must of been a tooth off or something. I cant believe that sensor would effect the car like that. You would think that they would make it fit just one certain way instead of having all that slack to where you have to guess around to position it correctly. Im just glad it was an easy fix.

Glad you got it figured out. Sorry no-one chipped in, this post must have been shuffled under the rug on a busy day or something.

 

The TPS is adjustable so that the ECU sees a certain voltage reading (around 0.5 V ) from the sensor when the throttle plate is closed.

The same sensors are used on a range of years, and several different engines. Because of differences in manufacturing, the base throttle plate setting on one engine may be slightly different than another, even if it's the same type of engine. Very small changes in the position of the sensor can make a big difference in what the ECU sees, as you've found out. So the sensor needs to be adjustable to account for those minor differences from one engine to another. There are also differences in manufacturing tolerances of the sensor. No two sensors will read exactly the same.

It is much cheaper to produce an adjustable component that will fit many different applications, than to make individual components for each engine.

 

The same sensors are also used on some Suzuki vehicles. Suzuki's engine management may look for a different voltage reading at base throttle position.

Edited July 15, 201114 yr by Fairtax4me

OK. That makes sense. Thank you for explaining.