HOW TO TEST TPS SENSOR (THROTTLE POSITION SENSOR) WITH A MULTIMETER P0120 P0121 P0122 P0123 P0124 

I watched it for my car but I'm working on a bike and l learned something very precious. Thanks mate!

2001 Grand Prix with a 3.1-liter motor, started idling high after good and warmed up. No codes at the time. When motor would idle too high, 4T65E trans would shift super late under light throttle. About 25 MPH and 2,500 RPM before it would hit 2nd. gear. Was OK the next day. 3rd. day, high idle and late shift again! This time the check engine light did come on. Code P0121. Scanner TPS angle percentage at idle shows 0 sometimes, and sometimes 0.39% and ~ 100% at WOT. One time while sitting there idling fine, ~ 700 RPM, all at once the idle kicked up to ~1,300 RPM all by itself. I looked at the scanner, now TPS angle percentage went up to 2.75%. From my readings it looks to me like the sensor IS receiving the 5V reference, and my ground in good, and my reference voltage is changing and being sent back to the ECM. My voltmeter is at my buddy's garage right now, so I could not do the voltage testing at the TPS connector, as you have outlined. I'm ready to take a chance based on my findings, and just install a new TPS. What do you think? Reply

This is a part to just change on most cars. If its not bad now it will be soon enough. Good to test the new one before you put it on. sometimes parts are junk out of the box.

Show us how to test the Alternator, and make it simple and easy

Why am I getting 5 volts on 2 pins on wire going to tps?

A bad TPS can also cause a clunking noise when shifting into gears.