2001 Tiburon

I have spent about 700 dollars at various garages around town and nobody can figure this one out.

This problem with the tranny was intermittent but now seems to be permanent.

I used to be able to restart the car and the problem went away but that does not work anymore

Transmission was shifting erratically and now is in limp mode.

CEL is not on.

I am focused on the TPS now and when I tested it today something looks wrong to me.

I suspected the TPS harness connector was bad so i cut it right off and started probing the three wires with the multimeter.

When probing the three wires with the TPS disconnected I have good ground continuity to the centre wire and the input voltage is good at 5 volts.

The output wire however reads 5 volts also when it is disconnected from the TPS and I dont think that is right.

I think the output wire is shorted somewhere in the bundle but before i start ripping out all the wiring searching for a short i wanted to make sure my logic was right and that i have not made a mistake and gone down the wrong path.

does it makes sense that my output wire is reading 5 volts with the TPS disconnected and that their is a short somewhere in the wiring harness?

I am concerned that i am going to lose all the money i have invested trying to fix this car.

if anybody has an opinion i would really like to hear it.

Thank You

Mark

 

I had the same thing happen a couple of years ago and I changed the tranny fluid and

the problem was fixed but that didn't work this time...

When the problem happens I can put the car in neutral and shut off the power and

coast. Then I turn the key back on and when i put it back in gear everything is ok for a

minute or so and then it down shifts awkwardly and will not go pass second gear.

 

Not sure what the problem is with the transmission.
But, testing the TPS ... the test to see which wire is the output wire is to back probe all the wires with the connector on the TPS sensor.
Two should have voltage and one should be ground/return.
When the connector is taken off the TPS sensor, One of the two wires with voltage should drop to zero ... indicating that is the output wire.
So, no, it doesn't make sense to have reference voltage on it while being disconnected.
There seems to be a short somewhere.

If the VSS (vehicle speed sensor) is also on this reference voltage then it can cause the computer to put the transmission into limp home mode

Good luck

 

Thanks that is good information confirming that 5 volts should not be present on the return side of the disconnected TPS.

Thank Your for that - very helpful!!!

That would also explain why the radio was turning off and on all the time and also some of the dash lights used to flicker.

I am going to guess that the return is being shorted by the 5 volt input power and the computer thinks it should downshift all the time. That's why there is no CEL

I guess I could drive around with the pedal down to match what the TPS thinks is going on

I looked at where the bundles of wire come into cabin and it looks like a real nightmare to go through those wires without taking a lot of stuff apart over many hours. I don't see anything resembling pin 73 in there.

I am going to try and probe with a cable finder and see if I can find the short somewhere. Frankly I am not that optimistic about finding it but I cant give up now.

if anyone has any tip tricks or insight please post. otherwise it will be me flying blind looking for the needle in the haystack.

Thanks again avisitor that really helps

 

Usually a shorted wire can be found in the engine bay.
Look for any wires near the exhaust pipes or wires near metal anything
It rubs and soon shorts out. Move wire bundles around to see if the short goes away
That may mean to keep a volt meter on the 5 volt reference and move wires around
It can show if you found the right bundle.
Good luck

Edit: A wiring diagram can be a big help when looking for shorted wires

 

Fantastic - That information is priceless - I actually think I might be able to find it now and

have the car back working again ! Thank You again

Hopefully I can write back again with good news shortly (no pun intended).

 

I stripped back the wire protector and got near the firewall when I noticed the first problem.

The return wire is attached to three different wires all twisted together and professionally soldered. That is definitely not in the wire diagram

The three wires are all color coded the same as the TPS return wire - white with black line.

One of the three wires connected to the tps return wire goes to the sensor that tracks how fast the right front tire is turning.

Another of the wires connected to the return wire has 5 volts when the key is turned.

So that is completely unexpected.

Oh there is more - when I disconnected the three wires connected to the tps return wire - the blue 5 Volt TPS input wire does not read 5 volts anymore.

I havent got a clue what to do now as the wires dont match the schematic and are not connected in a way that makes any sense.

I think I am just about done here.

 

Well I took a break and rested my eyes and bit and went back to look at the wires.

The wires on that wheel speed sensor are very close to the color of the TPS return wire.

The TPS sensor is green on white and the wheel sensor is black on white.

I rewired everything the way I think it is supposed to be and I still have 5 V on the TPS

return wire so I am going to keep going and try to figure why that is because it appears

to be something else I have not found yet. The wheel speed sensor was wired to the

TPS return though - weird.

I tested the TPS with the multimeter and it works fine without the 5 volt on the return

wire and the CEL is not on so might as well keep going.

 

It sounds like someone tried to bypass a fault by rewiring it.
I am sorry. But, it is beyond me now.
Personally I would try to get things back to the way they are suppose to be and diagnose the real fault and fix that.
Good luck to you.

 

Apparently what I was told about sensors and their wiring doesn't apply to all makes and models.
Some have a reference voltage and the sensor pulls down the voltage
Others have no voltage and pull up the voltage

I am very sorry if my information was wrong.
My Elantra uses a 5 volt reference on the TPS and the output pin does have 3.5 volts when disconnected.