New APPS sensor installed now random Dead peddle 5.9 C. Could it be ecm , alternator, or ground issue.?

Edited September 1, 20195 yr by 200k
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Dead pedal is typically either APPS or a VP44. Limited pedal is typically a ECM.

 

Dead pedal is when it idles only with no throttle response.

 

Limited pedal you can drive the truck but limited to low speed typically.

Peddle gose dead, goes to idle and comes back.

My transmission would shift between over drive and top gear then I move a ground that is over the alternator and the issue gose away till I got Po121 low voltage , replaced APPS got 5v. But now po121pd

There is the W-T ground mod you need to do. I've got to ask which APPS did you get?

Duralast from AutoZone.

Most likely a poor quality APPS with electronics. Stock APPS has electronics to select the IVS (Idle Validation Switch) for which mode of operation. Now Timbo's on the other hand is a completely true mechanical APPS and has ZERO electronics. 

 

As you can see here is totally based on bell crank angle and not on voltage. Once it crosses the boundary from idle to throttle the logic toggles automatically.

 

Not like the Stock APPS... As you can see the stock APPS has electronics to detect voltages and set the logic of the IVS switches. This in turn notifies the ECM of what mode of operation either THROTTLING or IDLING. If in idle mode then the ECM ignores the APPS sensor and uses its own internal idle software. Then with the voltage rises above the set limit then the IVS flip flops and then tells the ECM to watch the APPS sensor voltage. 

The part was $80 it seems to have stopped the confused overdrive, but now I get a dead pedal goes to idle and comes back after about 5 second's. So the timbo you say, I will try it and hope they take it back it if it doesn't solve my issue, I am not wanting to pull the ECM.

I think I should get a full diagnosis $200. Do you think this will prove out a new bad or wrong APPS or ECM?

Thanks for the info

When I took the truck to the transmission shop when I first had the confused overdrive symptoms they told me I needed a new trans.. So I don't trust anyone.

All you need is a live data tool like a OBDLink LX or ScanGauge II and monitor the TPS signal if the numbers a steady and not jumping around then they APPS is good. If the TPS drops to ZERO or suddenly jump up in value while held steady then the APPS has failed. When the ECM detect a value out of range the ECM automatically disconnects from the aPPS sensor and does the dead pedal and also at the same time throws the code. 

 

P0121, P0122, p0123 are the common codes.

Edited September 7, 20195 yr by Mopar1973Man

On 9/7/2019 at 8:12 AM, Mopar1973Man said:

All you need is a live data tool like a OBDLink LX or ScanGauge II and monitor the TPS signal if the numbers a steady and not jumping around then they APPS is good. If the TPS drops to ZERO or suddenly jump up in value while held steady then the APPS has failed. When the ECM detect a value out of range the ECM automatically disconnects from the aPPS sensor and does the dead pedal and also at the same time throws the code. 

 

P0121, P0122, p0123 are the common codes.

My 99 3500 has the dead pedal issue with a p0121 code. My edge monitor can read apps position and the value doesnt jump when the code comes active. It stays consistent with what the pedal is actually at. I followed your ts steps and get 5v at pin 5 in the apps connector, and the ground is also good at pin 4.  Ive owned the truck 2 months max and this problem has come and gone 3 times. Supposedly the apps was replaced a week before I bought it, so I'm going to try the timbo sensor, but if that doesnt work will that point more toward the ecm?

I have been thru a few bouts of dead pedal issues over the years. Even with those TPS codes it never turned out to the TPS. The first bout was the VP and fuel pressure. Many years later several weird surging and dead pedal issues. I did have a problem with the 5v sensor wire being damaged. Fixxed that and it helped. But the biggest 2 things I did was clean up my charging system and all of the connections, l made all new battery cables which may not be necessary. I then did the WT ground mod. All this was 3 years ago and not one problem since. 

ECM? Possible but I think unlikely. I would not replace it based dead pedal and TPS code.

When I bought my truck PO had just fitted a tps, one of the el cheapo $ 20 chinese things that needs a harness adaptor to work, it still had a fault, I checked output with a Snap On Brick and at one point in pedal travel voltage took a very quick trip to the funny farm then came ok just as quick, it set a code every time but as long as it wasn't held at the bad spot it was fine, got it as a spare as it would get me home, didn't fit a timbo as at the time I hadn't found this place, got one from Rockauto and touch wood its been ok. Point is even new can be faulty