TPS low voltage at signal wire

[clickittyclank]

1987 GMC Sierra Classic, TBI 350

Got a code 22 for low voltage at the throttle position sensor and thats exactly what I'm reading with the meter. 5v at the white wire, ground seems good, but .1v at the signal wire which is way low. Smooth increase with throttle up to 2.3 wide open which is again way low. Wiggled the connection a bit to see if anything would happen and it dropped to .06v. Seeming like a possible connection problem but not sure how to proceed. Is it possible to tighten up the female receivers on the TPS itself? Any way to verify 100% that it's a connection issue and not a failing TPS? Appreciate any help. Think I am almost at the finish line!

 

[Matt69olds]

I assume you have verified the throttle is actually opening far enough to get a higher reading? Is there a tps adjustment?

Remove the tps, see if you can move the lever enough to get a higher voltage. If 2.3 volts is as high as it goes, I’d say you have a defective tps.

 

[YakkoWarner]

Some TPSs are adjustable - 0.1 is way too low - often if you loosen the screws holding it to the throttle body you can turn it slightly and set the low voltage to where it should (0.5 ideal). One of my screws stripped out so I can't adjust it the "normal" way, the plan "B" is to use a pair of needle noses and very gently and slightly bend the little arm that sticks out of the TPS itself (and hope it doesn't break off). I was able to get 0.48 fully lifted which is close enough to 0.5 to work.

 

[clickittyclank]

@Matt69olds I had not checked on the actual throttle. This all happened after unplugging it while running to see if it was causing another issue. I'll try testing it with the sensor off and seeing what the reading says. Had an issue with it before but seemed like I had it fixed as it was just a bit stuck from sitting. Once I got the arm moving freely again the TPS readings were in range.

@YakkoWarner this one isn't the adjustable sort but I've read on bending the arm. Might have to do that as a last resort if im going to order one anyways.

Thank y'all for chiming in.

 

[Ricko1966]

You can disconnect the electrical from the tps,use a junk phone charger and jumper wires for a 5v source.

 

[gmbellew]

TPS and MAP share the 5v signal wire and TPS and CTS share the ground wire. If you verify ground and signal wire are good at the TPS, and the other sensors are not throwing a code or having issues, I’d highly suspect the TPS is the problem. I’d replace with a AC Delco branded one. You may or may not need to bend the tab a little when you get it. A lot of times they seem to read near the upper end of allowable idle range. Anything in the .5 to .8v range at idle is fine. More than .9ish I think will start to mess with the ECM.

 

[clickittyclank]

@Ricko1966 had to go check a phone charger. Never realized those were 5v, nice info. You've done some tinkering before haha.

@gmbellew I was wondering where the ground was for the TPS. Thanks for sharing. The wires all read correctly except the signal. Thinking about it though, since I was getting a reading as I increased the throttle and it went from .1-2.3v smoothly I'd imagine the connection wasn't the issue. Don't see how I would have gotten much of a reading if it was. Starting to lean towards the TPS being the issue as well.

 

[77Dmax]

Check/clean the grounds before buying anything.

 

[clickittyclank]

@77Dmax the grounds are probably the only thing I'm pretty confident in haha. Just didn't know exactly where that one grounded. Went to town on all of them that I could find throughout this process.

TPS seems to have solved the issue! glad I came on here and asked before messing with the wiring and connector. Swapped it out, tested voltage which was in range and fired her up. Thank y'all again for all the help. Learned a lot from y'all and from diving in under the hood throughout this process. All thats left is a pretty obvious exhaust leak which I hope is an easy fix and snapping a photo for the profile.