Dodge Cummins Diesel Forum banner
1 - 14 of 14 Posts

·
Registered
Joined
·
198 Posts
Discussion Starter · #1 ·
Got a dead pedal twice over the weekend and the p0121 code is what it gave me, been looking through the forum and Google and have already reset my apps, and tested for alternator ac noise and that was in good shape. Last time I got a dead pedal was a little over a year ago. Seems to only do it when on a long drive (2-3hrs or more) before I go throwing an apps at this, are there any other tests or anything I can do to make sure that is what I need?
 

·
Mopar1973Man.Com
Joined
·
26,259 Posts
  • Like
Reactions: Clunk

·
Registered
Joined
·
22,326 Posts
What apps is on it, Factory, Timbo or other?
 

·
Registered
Joined
·
198 Posts
Discussion Starter · #4 ·
As far as I know it's factory. I bought the truck with 183k and now have 235k, I'm not completely sure what was changed prior to me owning it. It could be a factory VP as well for all I know. I will be running those diags tonight after work.
 

·
Registered
Joined
·
22,326 Posts
If it is Timbo or Geno's it will have a 3" pigtail hanging down to plug into under the bell crank. Factory and others don't have the pigtail. The harness plug goes up under the bell crank housing. Just look.
 

·
Registered
Joined
·
198 Posts
Discussion Starter · #7 ·
According to the diagnostic instructions I need a new apps
 

·
Registered
Joined
·
22,326 Posts
Apps is easy to test and confirm. With a pin in the plug to the apps at #3lin hook up a voltmeter and run it to the cab with jumper wires. You can also go through the insulation on the same wire to monitor. Monitor it while driving. While sitting at idle it should read steady at .519v or less. It should graduate steadily and smoothly to around 4 volts at WOT. In between accelerating/cruising it should hold as steady as your foot is. Cruise will constantly be adjusting it self. See what that voltage is like be for replacing apps. If the apps is producing good correct clean voltage it is not the problem. Bad apps are usually two things, a wear gap in the rheostat causing skipping acceleration or dead pedal or too high of idle voltage causing surging because the ecm thinks you are accelerating when you are not.
 

·
Registered
Joined
·
198 Posts
Discussion Starter · #9 ·
Can this be done by watching the voltage via scanner? I havnt checked that part of it but following the diag instructions on Mopar man's page, it's apps. It does have a "skip or jump" around 75-80mph 2400ish rpm. I always thought it was the way I had my quadzilla set up though
 

·
Registered
Joined
·
22,326 Posts
I don't know if the scanner works or not, I have not and don't do it that way. I do not know if it reads the apps or in the ecm. I am not saying it is not the apps, but that test does confirm if it is the the apps vs the ecm or VP. maybe the scanner does read that wire, I do not know.
If it is the apps, Mopar and I disagree on which apps to use. He likes the Timbo buy the idle voltage is over 6v and not adjustable. I am a firm believer it should be set below .519v to match idle validation specs. You need one that is adjustable like OEM or other. I like the Wells TPS as it is adjustable and has a magnetic reader rather than the mechanical rheostat that has worn out in yours. It does cost some more but not as bad as some. Watch:

 

·
Mopar1973Man.Com
Joined
·
26,259 Posts
Still running a electronic device that is very touchy about AC noise issues using Wells APPS. Timbo on the other have is completely mechanical and has ZERO electronics. So the rheostat could wear out over time still nearly half the price and no electronics. Just food for thought. There is a lot of people running Timbo's APPS without any issue like myself its been running for many years now trouble free.

And as for voltage set there isn't one on Timbo's because it mechanical it all about making sure the IVS is in the IDLE position that all. Like mine is at 0.633 volts current no issues. High idle and exhaust brake function all working.
 

·
Registered
Joined
·
22,326 Posts
The 6.33 is still more than the idle validation should be sending out. The ecm and trani do not want to see that high of voltage and think it is not idling. Maybe it is because of the year or if you have manual that you have no problems.

I have had no electrical problems with the Wells at all. The magnetic sensor should be more reliable than the rheostats that do definitely wear out hand have problems. It is a simple reader, not a hard drive. I am surprised at you support for Timbo, even though is has been OK for you being that it does not meet factory specs(.63v) and needs an adapter plug, and how many oem were replaced when AC was causing problems and getting blamed on the apps.
I suspect that if you have manual and the 02 ecm may see that voltage differently than my 99 and before. It does usually show up in the earlier years. I will give you it does not affect everybody, but there have been several with the Wells that have fixed the surging who had the Timbo but not others.
 

·
Mopar1973Man.Com
Joined
·
26,259 Posts
The 6.33 is still more than the idle validation should be sending out.
It rheostat is ignored as long as IDLE is selected. IVS is not electronic like OEM or Wells it just a toggle switch.

As for OEM is all electronic like the Wells...


As for the Timbos its just a rheostat and two switches the actual bellcrank angle is what triggers the IVS not voltage. Again, idle voltage has zero to do with IVS on a Timbos. On Wells and OEM you MUST set the idle voltage because that is what triggers the electronic switch like seen above to toggle the IVS.



No matter how you want to slice this you must understand the IVS tells the ECM if the throttle is IDLE or THROTTLING. So back to Wells ands OEM its voltage based being its electronic. Timbo is angle based since there is ZERO electronics involved. Also there is no harm in having .6xx volts for idle voltage as long as the IVS is in the IDLE position because the voltage is ignored. ECM at that point uses internal idle software that is why you can't adjust the idle because idle speed is set by coolant temperature and IVS switch of the APPS nothing more...
 

·
Registered
Joined
·
22,326 Posts
What I can't get you to understand is that whether it is mechanical or not it is still sending .63 rather than under .519 to the ecm and trani. So they do not see it as idling, they see it as accelerating.
 
1 - 14 of 14 Posts
Top