Some of you have found that your Manual Trans 03 or 04 trucks do not have the APPS assembly bolted to the side od the engine. Yours will be under the battery tray. You'll have to remove the drivers side inner fender well to access it.
I used to sell these sensors (OEM Mopar) but most every customer that purchased one, it did not solve there problem. There check engine light was still on and they felt the NEW sensor was defective. That lead to warranty requests, upset customers and a loss on my end.
If you are having an issue with yours and want to replace the sensor here is the Mopar part # 53032456AE if you do a google search just use the part # and you'll find one cheaper than your local dealer.
Here is technical info on how it works and how to test it. Below is a Youtube video
The under battery APPS consists of 2 variable voltage signals for acceleration. Below is a bench test using a 5V power supply and two voltmeters. The left meter is APPS signal #1. The right is APPS signal #2.
Notice that the APPS signal #1 is always double the voltage of APPS signal #2.
If want to test yours, get 2 voltmeters and back probe your ECM plug. APPS signal #1 is ECM pin #14. Signal #2 is ECM pin #16
NOTE!! Both of these are checked on the 60pin connector(the one closest to the front of the truck).
Your start and finsh voltage value may be slighly different. The important thing is ECM pin #14 is double the voltage of ECM pin #16, the entire travel of the accelerator pedal.
UPDATE I have recently found that the problem really is within the stock wiring harness. I have made a DIRECT harness from the APPS sensor to the ECM main plugs.
The harness comes with 2 of the extraction tools needed to remove the existing wires from the main ECM plugs. Instructions with a chart and picture of the wires you will be removing and which color wire you will be inserting into the correct PIN# location to the ECM plugs.
I receive a high volume of phone calls from guys who want to "run the symptoms of their problem past me". I want to say that of all of the symptoms I hear can be different. The check engine light usually comes on with a 2121,2122,2123,2127. Sometimes no engine light but a dead spot in the pedal, maybe an acceleration issue when it's cold outside, when on a bumpy road, maybe only when it's damp or raining outside. You have replaced the sensor 6 months ago and now you think it's the sensor again...
First and foremost put a direct harness on it!
I have made well over a 100 of these and 90+ % of times this has solved the problem.
If your problems go deeper then odd acceleration issues or the check engine light with APPS codes then there is a chance there is an internal ECM issue and at that point you will need to go the dealer or find someone in your area that is familiar with this ERA Cummins trucks to troubleshoot the problem.
These will usually ship 1 day after ordering as I make these upon request