Testing TPS - Throttle Position Sensor

Maybe this is not a new discovery, however, in my searches for testing I had not seen this, so I just wanted to share this in case it might help someone else.

I have been chasing a high, rough idle. Had tested the TPS via scanner & multimeter, both resistance & voltage. As I rotated the cable wheel, all seemed to go smoothly. The same for a quick check of resistance & voltage numbers.

The scanner showed that at times the throttle would close .4v higher than what it was set at. Big deal? I didn’t know, however to me it warranted another check.

Again, it passed the cable wheel test. I was wondering if maybe the wheel was getting hung up, so I focused on that.

My start up voltage is .49. Closed is .45. Here’s what I noticed. At the start up position, it stayed at .49. However, if I closed it & then let it back to start up position, the voltage started fluctuating, .49, .48, .49, .48. So I held it closed. Waited a few seconds, .45, .46, .45, .46. Wait, there’s more. For ha-ha’s tried .50. Waited a few, .48, .49, .44, .50, .43…. It actually went below my closed voltage. That was enough for me, meaning I didn’t bother checking any other spots.

Then to rule out (or in) the connector, harness or ECM, I checked the resistance to see if it did the same. It did indeed.

Is this the answer to my ongoing idle issues quest? I dunno. We can only hope. I have a Toyota TPS on the way….

 

Hello Kristi with a K . Any luck with the new TPS?

 

Ha-ha! That feels like forever ago…. I can’t say it hurt? Seems it’s folded in with other things I did, like sending out the throttle body to get rebored & all new hoses…. It’s weird. My focusing on the idle got preempted by other stuff, like the transmission, exhaust, engine noises, etc, meanwhilst the idle has gotten better….
Probably not much help to you though….