Problems with tps

[bigred4x4]

Hey guys I'm having trouble trying to diagnose my throttle position sensor at the plug while it's disconnected reads normal but when I connect it and backprobe the connector it's about .70 volts too low on the signal side (4.3v) at WOT and once it's connected the reference is reading 4.02 v ...... Thought it was a bad sensor so I replaced it but I'm still getting the same readings the only driveability problems I have that are noticable is the clunk when coming to a stop but when I reset the pcm it doesn't do it until it completes it's drive cycle. And iv been told that this is most likely caused by tps problems.

Is there something else that could cause voltage drop ? Does the sensor ground itself in any way to the throttle body?

I've also noticed some slight changes in tps % data on my scanner.

 

[bigred4x4]

I'm going to try to take apart the connector and clean the contacts. Also I thought my alternator was going out but come to find out I have a 1.5 v drop on the engine so I'm going to add a ground and clean existing ground straps I'll report back hopefully this is all just a connection problem unless someone has further ideas.

 

[96eb96]

probe the voltage at the PCM end. Isn't Vref = 5? Could be a corroded wire maybe? Modern TPSes are not common to fail.
I doubt the sensor grounds itself thru the TB, it is surrounded by plastic.

 

[bigred4x4]

Well reference at the plug is 5 volts until I plug it into the sensor then it's 4.02

 

[david4451]

Have you touched the screw on throttle body that alters idle rpm? Also what is your idle rpm, should be 500 to 600 on hot engine.

 

[Turdle]

Check the 0 volt line in reference to ground, make sure it is indeed 0 v

The sensor is not grounded. The low potential is a 0 volt line. Probe all connections with black test probe on true ground .

Idle voltage at output
WOT voltage
0 v line
reference ( 5v) line

Then remove the connector , measure reference, output and 0 volt

Post the results please

 

[bigred4x4]

I got 5.02 volts as reference and .1 voltage drop on the ground at the plug while it's disconnected I plug it into the sensor and have 4.02 volts reference (5.02 if I ground to battery) .94 volts at signal closed and 4.22 volts at WOT.

 

[bigred4x4]

And my idle is normal about 550/600 rpm warm.

 

[Turdle]

The only thing I can think of to account for the voltage drop under load would be a short or bad connection. short has been ruled out.
You mention transmission work.If you haven't tried this already, How about checking the transmission harness plug. Big one right in middle of firewall. loosen the bolt, take it apart, check that all pins line up and tighten it back together. Try the same thing with the PCM connector while you have the tool in your hand. Compressed air blown over the pins doesn't hurt.

 

[bigred4x4]

That will be next on my list if cleaning the plug doesn't work. It would be nice to return that tps and get my $40 back lol. I'll report back tomorrow I'm going to do that plus add and clean engine grounds plus I have some sliders to install. Probably going to be another long weekend lol.

 

[bigred4x4]

Ok so I got the sliders in but didn't have time to mess with the tps but the new one is installed and I never reset the computer and I did drive it around a little bit Saturday and didn't notice the clunk at all so hopefully it stays that way it's worth the $40 but at the same time I'm probably going to mess with it a little more to see if I can't get the old one working right.

 

[bigred4x4]

Another update cleaned the grounds and added a new one. My alternator which o thought was going bad. (13.3 charging volts) is now back to 14.6 and still no problems with the downshift clunk and the engine runs smoother now it used to stutter a bit with light throttle. Seems that problem is gone...... so My advice to future readers is check for voltage drop between alternator and battery before replacing charging system components!