Looking for the ground to MAF,tps,ect

[cali+Mocasho+]

Got and engine light and figured it was my tps again but I installed a new one ant still don't notice an engine idle change. Same with MAF I pulled that just to see if I could notice a difference and nothing. On top of that I pulled codes and got engine coolant temp ping to high. Ground issue? I mean the car still responds well just not the best it can.
1991 sho

 

[cali+Mocasho+]

pulled the power and no more engine light. Probably should of done that right after I installed the new tps.

 

[cali+Mocasho+]

Still would like to find that ground.

 

[rubydist]

well, that circuit doesn't exactly have a ground.

I don't have a 91 manual, but according to my 92 manual, circuit 359 (GY-R) supplies power to:
knock sensor
throttle position sensor
coolant temp sensor
dpfe

the return from each of those sensors is read independently by the pcm to determine the state. I would look at the voltage on circuit 359 as a place to start.