This one really has me baffled! I read the codes for my 1996 F250 7,3L Diesel and it showed that the TPS is bad. Installed a new one still the same condition and malfunction. I took off the pedal, cleaned it as well as the small micro switch, ohmed it out that works and installed it. Cleared out the trouble code started it up and the same P0221 came back. Also had P0476 (back pressure) P0123.

I then took off the TPS, manually depressed the pedal so the relay would engage and turned the TPS with a screwdriver. No change All of the fuses are good under the hood and in the interior fuse panel.

Is there a relay under the hood (if so where) that does not come up in the malfunction codes? Anything else I am overlooking? All other tests I have performed on it do not show any other malfunctions.

 

Maybe a stupid question but are you sure that code P0221 is referring to the TPS and not the IVS (Idle Validation Switch)? Have you ohmed the IVS to ensure that it is functioning as it should be?

 

You need to check if the IVS and TPS are putting out a signal.

Click on the blue
https://www.ford-trucks.com/forums/1...nsor-info.html

 

I took off the IVS, sprayed contact cleaner into it, and ohmed it out, works great, on and off. Placed it back on the pedal, opens and closes, clicks...so I know that there is an on/off state being generated.

Also ohmed out the old and new TPS. Resistance was higher in the old TPS versus the new one. 3.6 ohm between the outside pins and 167 ohms from the end to center pin. The old TPS had a reading of 600+ ohms from the end pin to center. Thought that may be a problem.

 

Check to make sure the voltage is being sent to and from IVS

Check to make sure the tps is sending voltage

I'm not say your parts are bad. Check to make sure the are doing there job will tell you if it's a part or issue upstream

 

Measured 12 VDC on the IVS and 5 VDC on the TPS. What is the voltage that should be on the TPS across the pins? Is there a fuse somewhere that could be blown? 5 VDC seems low...

 

With key in on position and TPS plugged it.
Put the hot lead in the middle wire
Ground to battery
Slowly push down in go pedal watching the volts
At idle you should have 0.7v
Wide open throttle should be 4.5v

 

Measured from the center pin to ground...measured up to 4.7v when fully depressed from under a volt. Is there a diagram to where this out put goes to? A relay maybe.

 

On the IVS you have 12v coming in and out ?

 

Yes. I measured it on the plug contacts.

 

Whatever you're using to get the codes, it reads live data, right? Have you tried just watching the TPS value as a %age with the key on, and slowly pushing the pedal? You should also be able to get the 1/0 status of the IVS, and determine when it switches on relative to the pedal position.

 

I am using a Snap-on Modis to test this. Ill figure out how to watch this live.

 

OK. I ran the KOER test and it came back with a:
P0476 Exhaust Pressure Control Valve Code

The KOEO test cam back with a:
P0221 TPS B Perform Code

And the codes in memory were:

P0123 and P0221

 

Also could see the pedal voltage change when depressed and the change of state in the IV switch.

 

If you can see it changing with a scanner then that means the PCM is seeing the tps and ivs work.

I'm lost now.

Do you have a chip?