Hello all
1992 Bronco 5L
400,000K
Error code 122 Low voltage @ TPS
My question is how to repair????
We had a bunch of different faults but can't seem to shake this one.
Have replaced the TPS & EGR sensor
Gas engine so TPS apparently not adjustable.
Any tips would be much appreciated.
Thanks in advance!!
Cheers!!!

You have to physically measure the voltage in and out of the TPS to determine where the problem lies.

What engine does it have?




78 Corvette Pace Car For Sale-18k mi orig-Florida

Its a 5L
Measuring the voltage will help determine where the problem lies????
Cheers!
Don

Unplug the sensor with the key on and measure the voltage between the gray with red wire and the brown with white wire and you should have 5 volts.

If that is OK plug it back in and measure between the gray with red and the gray with white and you should have between .5v and .75v at idle. As you slowly open the throttle, the reading should slowly increase to just under 5v at Wide open throttle.

Let me know what you find.




78 Corvette Pace Car For Sale-18k mi orig-Florida

Will do. Have to find a multi meter so might take a bit but I will return.
Appreciate the help very much.
Back in a while.
Thanks again!
Cheers!!

Hi there
Sorry for not getting back last night but couldn't get my meter back from my buddy. Will have it after work tonight & will post my findings. Easy to understand how to test the circuit when the connectors are apart, but what is the best method to test when they're closed???
Thanks & regards,
Cheers!!

Use a paper clip or needle to backprobe the plug.




78 Corvette Pace Car For Sale-18k mi orig-Florida

Thanks for the tip!
Will post the readings later on.
Cheers!!

A little shot of carb clean on the backside of the connector will help the probe slide in. I tried di-electric grease which lets the probe slide in real easy. the problem I had were my leads were too heavy & would pull the probe out if I moved my scope.

Wow that was kinda brutal. Thought I was losing my mind & not able to get readings on the 2nd test.
Finally got it & this is what I got.

With the harness disconnected I got the 5.01V across the designated wires
With the harness reconnected I get 2.1mV across the designated wires & no change when opening up the throttle.
??????
Cheers!!

You were measuring different wires when it was plugged in, right?

If you did that right it's indicating a bad TPS.

Try one more test
With it plugged in, repeat the second test but instead of using the gray with red, use the battery ground and see if you get any different results.




78 Corvette Pace Car For Sale-18k mi orig-Florida

Hmmmmm
Ok will try that. I did measure across the other 2 wires on the 2nd test. It's also a brand new TPS on there right now. I guess it could just be a bad one. When I 1st started this venture I had several different codes to deal with. Replaced the EGR sensor & the TPS. Got rid of everything else but this 122 code. Before starting this repair, there is an adjustment screw on the throttle that had been adjusted out to open the throttle flaps more & run smoother/idle better @ low end. Should I have backed that off again before installing the new TPS???? Or would the new TPS compensate for that. With the new TPS installed I had to open it a bit more in order to keep the motor running. Now I get a hard shift between 1st & 2nd, the motor runs fairly smooth & the tach seems out of whack by approx 500 RPM compared to the previous set up.
Cheers!

I'm suspecting that you either damaged that TPS when you put it on or it's installed wrong.




78 Corvette Pace Car For Sale-18k mi orig-Florida

Do you think I should try taking it off & then backing the adjustment screw til it comes back around to fitting the TPS again???
Cheers!!

The base idle is a whole different adjustment and there is a procedure for that but it should not effect the TPS installation. There is a set of cogs that have to line up correctly with the TPS so it can rotate it. If the cogs are on the wrong position, it will just break when the throttle is opened.




78 Corvette Pace Car For Sale-18k mi orig-Florida




(This post was edited by Hammer Time on Sep 18, 2009, 1:15 PM)

Sorry, been away a while.
Figured out my TPS problem
Thanks all for the help.
Much appreciated.
Cheers!