TPS voltage test

[SuperRob]

Hey guys, I was cruisin the posts as usual, and saw one or two that said that the screw on the throttle body was not a throttle stop but for the TPS adjustment.

I had a look in the tech library and couldnt see anything on how to test it and adjust it. Cause I'm pretty sure that I've buggered with it over the years. If someone could advise I'd greatly appreciate it.

Thanks

 

[MAKG]

Should be about 1V with the throttle closed.

 

[SuperRob]

Where do you probe it from? It only has the plug doesnt it? How can you probe the sensor for voltage when the plug is unplugged....theres no power delivery is there?

I'm just going by what I remember seeing, I'll have a better look tomorrow and probably figure it out myself.

Thank MAKG

 

[RobbieD]

There's a good way to connect your meter leads without hacking the wires. The connector that plugs into the TPS has a rubber weather seal on the back where the wires go in. Just use a small flat-blade screwdriver to start this rubber plug out, then needle-nose pliers to pull it out of the connector. Now you can see the terminals, and you can slip your probe leads right in beside the two you need (the connector is still plugged into the TPS- you're probing from the back). I've done this on my '90 and '94; I think the '89 in your sig will be the same. I just tested the TPS on my '94, and the range was .8 to 5 volts. Don't remember, but I think the '90 was about the same. When you're done just push the rubber weather seal back in place.

 

[SuperRob]

AWESOME....thanks!

 

[MAKG]

There is an easier way. I do this all the time.

Take a straight pin, like the ones in your grandmother's sewing kit, and stick it CAREFULLY between the wire and insulator. This is called "backprobing" and if you do it right, it won't damage anything and you won't even be able to tell it has been done once removed. In many (though not all) cases, it's possible to do this without even disconnecting the connector. The head of the straight pin can then be used to connect alligator clips to. WARNING: don't short it to anything. Sometimes that's benign, and sometimes it blows things up (especially the PCM or fuses), but it's NEVER good.

As for where to connect the TPS, they are almost always three-wire potentiometers. One wire is ground, one is power (5V -- NOT battery power), and the third -- usually the middle one -- is the signal. It's a good idea to measure all three with respect to the negative battery post, just to be sure. The measurement should be made between signal and ground. This should be the same as between signal and battery post. If it isn't, look for a grounding problem.

Most voltage measurements are done with the circuit completely assembled and powered.