I am trying to find out the differences in the 89 si wiring and the 90 si wiring harness to the ecu. Because I am have problem with my tps senor not reading. I know the tps work it came off a 90 dx motor with 87k

 

The tps on the si is different than the one on the dx, what you need to do is swap the outside wires and it should work. good luck