Backwards TPS Readings

[Innovative Tuning]

As I installed my new standalone engine management system in the rally car yesterday I realized that the TPS sensor operates "backwards" in the Legacy Sport Sedan (at least in 91 and 92's). As you apply more throttle the TPS sensor voltage goes down rather than up as is the norm. I was reading about 3.7 volts at zero throttle and 0.7 volts at wide open throttle. I know the new age WRX's don't operate this way.

I reversed or "fixed" this by crossing the power and ground wires on the TPS sensor harness (wires 2 and 3 - the middle ones - back and red). If anyone else is installing a standalone ECU, this is something to keep in mind. Check with your dealer to see if this is necessary.

Disclaimer: Don't do this on the stock ECU!!! Your computer will think you have the throttle wide open when you're sitting at idle!

[mTk]

It's not just the turbos, my n/a 92 did this too, i think it was the reason for my flakey nitrous kit.


MK

[Legacy777]

that's normal for the first gen legacies.

[Bubba-Ugly]

In my 90 Legacy I noticed the same situation. I checked the resistance of the TPS, and discovered it was backward from the way Chiltons, Haynes, All-Data, and the Subaru '92 Shpp Manual descibed. THinking I had a biad TPS, I went to a junkyard and pulled a TPS off a '92 Legacy. It was the same way: max resistance was 10K ohms, closed throttle was 8.6K ohms, and WOT was 1.9K ohms.