Take for example the TPS. There's a coil (resistor) inside with a wiper that moves between the high volt and low (ground) volt reference that allows the signal wire to vary voltage proportionally between the high and low volt references depending on the wiper's position between the two. The wiper can't get close enough to either the high or low volt reference to read exactly the same as each reference.

It's kind of hard to put into words, but I don't have a diagram or anything to help explain.

 

great info thank you!!!!
quick question though, what do you guys think would be the cause of too much voltage on the signal return wire of the EVP sensor? Same results with a rebuilt ecu and original ecu….

im thinking of connecting a jumper wire from battery negative to the ecu pin 46 that controls the signal return to see if there’s any change in voltage….

thanking you guys in advance

 

start your own thread but sig return from the evp? What do you mean too high? And if your signal referecnce (5v ref) is normal, then its the sensor or a short to power on the wire. Probe the terminal for the wire and not the wire itself(depin the wire and touch just the terminal if possible) what do you get?

 

Unplug everything with connection to SIGRTN and measure voltage between it and battery negative. If voltage is present, there's a short to power somewhere in the harness. If 0 volts, plug in sensors one at a time until the SIGRTN voltage changes to pinpoint the problem sensor.