TPS Problems.....
Thread Starter
|
Freshman User
Joined: Apr 2009
Posts: 27
Likes: 0
TPS Problems.....
Well I have replaced my tps sensor three times now. my check engine light never has stayed off. So today I went out to test it with a multi meter. It shows its getting the 5 volts but on the other side of the sensor it doesn't show any voltage no matter where the throttle is. I then disconnected the plug and tested the sensor and the resistance reading was correct. Now I am lost. About the time this all went south the truck started down shifting and almost felt like it is slipping. Any correlation?
Senior User
Joined: Dec 2005
Posts: 253
Likes: 0
From: Beaver, Pennsylvania
Just a thought, when you are installing the new TPS, are u makeing sure it is engageing the flat tab comeing from the throttle body? When installing it you may have to turn it slightly to engage the tab. If you miss it the throotle is not moveing the TPS.
Logistics Pro
Joined: Jan 2002
Posts: 4,907
Likes: 39
From: suburban atlanta
Why did you replace it the 1st time? Did you test it with a DMM? Did you test the new ones with a DMM? Do you have 'reference voltage' to one lead? I *think* there are 3 leads: 1)5v, 2)signal ground and 3)signal. I have been wrong before, so you are warned.
A bogus TPS signal could have told the ECM that you have the throttle closed, so it would disengage the torque converter lockup, even if you are going down the road at 60. I don't know the age of your truck, but some have electronic controls for about everything the trans does. Lose a signal here, a voltage there and who knows. There is a pressure in some that is regulated by the engine values for rpm and throttle position. It will 'stiffen up' a shift, with WOT and high rpms by raising this pressure. If it doesn't know the throttle position, it could make shifts very mushy.
Connect your meter to the leads for signal and ground, and sweep the throttle through its travel, engine off. The ohms should change in a linear fashion. You can also do a voltage sweep test, with the key on, engine off.
tom
A bogus TPS signal could have told the ECM that you have the throttle closed, so it would disengage the torque converter lockup, even if you are going down the road at 60. I don't know the age of your truck, but some have electronic controls for about everything the trans does. Lose a signal here, a voltage there and who knows. There is a pressure in some that is regulated by the engine values for rpm and throttle position. It will 'stiffen up' a shift, with WOT and high rpms by raising this pressure. If it doesn't know the throttle position, it could make shifts very mushy.
Connect your meter to the leads for signal and ground, and sweep the throttle through its travel, engine off. The ohms should change in a linear fashion. You can also do a voltage sweep test, with the key on, engine off.
tom
Thread Starter
|
Freshman User
Joined: Apr 2009
Posts: 27
Likes: 0
Ok its a 96 ranger. I have done all of the test mentioned above and all see fine except the voltage sweep i get nothing. even with the sensor removed but still plugged in I get nothing when I turn it by hand. I replaced it the first time cause the CEL came on throwing a TPS code..
Thread Starter
|
Freshman User
Joined: Apr 2009
Posts: 27
Likes: 0
Well tried swapping one last time and still not picking up on the tps and sig rtn wires.... is it possible that there is a problem elsewhere? Wires maybe? This truck is a 96 with 54,000 miles on it.....
Thread Starter
|
Freshman User
Joined: Apr 2009
Posts: 27
Likes: 0
Well I think the sensor is reading. So I cleared the code and then didn't get half a block down the road and it threw the p0122 code again..... I am so frustrated..... I hope someone here has an idea......
Logistics Pro
Joined: Jan 2002
Posts: 4,907
Likes: 39
From: suburban atlanta
Way back when dirt was new, Ford made their 1st TPS. They also put a diode into the TPS circuit to prevent back EMF (electricity generated by a collapsing field). Initially the diode was put into the wiring harness, I THINK.
They then changed their mind, and put the diode out there in the TPS itself. And changed its cathode end for end.
They also sold replacement TPS with this diode to their customers.
It would not work because of the diode and its polarity. That presented a problem.
I would check to see if you have 'infinite' (lots) ohms in one direction and then flip the black for the red and check to see if the ohms are not so big. If so, you have a diode buried inside the TPS. Check the old one [YOU KEPT IT, DIDn"T you??? You NEVER throw something like that away until you are sure it was replaced with a good one] to see if it has the same ohm readings in both directions.
tom
They then changed their mind, and put the diode out there in the TPS itself. And changed its cathode end for end.
They also sold replacement TPS with this diode to their customers.
It would not work because of the diode and its polarity. That presented a problem.
I would check to see if you have 'infinite' (lots) ohms in one direction and then flip the black for the red and check to see if the ohms are not so big. If so, you have a diode buried inside the TPS. Check the old one [YOU KEPT IT, DIDn"T you??? You NEVER throw something like that away until you are sure it was replaced with a good one] to see if it has the same ohm readings in both directions.
tom
Thread
Thread Starter
Forum
Replies
Last Post
Mountain54
1987 - 1996 F150 & Larger F-Series Trucks
6
Mar 7, 2017 04:38 PM
Jonathan Stone
Small Block V8 (221, 260, 289, 5.0/302, 5.8/351W)
3
Aug 21, 2015 03:45 AM
