sammy340

Gents,

My APPS has been giving me issues for some time now, throwing the P0121 code every now and again and giving me the dead pedal until I clear the codes. Today, it threw the code again and this time will not clear for me. I'm thinking the APPS finally just died all together on me.

Anyway, I'm looking for some advice if this is the final sign of a completely failed APPS, or it could possibly be something else. Please let me know your 0.02 before I order up a TIMBO APPS.

Cheers,

Jeff

AlpineRAM

Possible reasons for p0121:

5-volt Supply Circuit Shorted To Voltage With Ignition On
APP Sensor
Idle Valid Signal (IVS) #2 Circuit Shorted To Voltage
Sensor Ground Circuit Open
5-volt Supply Circuit Shorted To Voltage With The Engine Running
ECM




I'd look at the wiring related stuff in 1, 3, 4 and 5. Had a truck where an intermittent fault in the map sensor shorted the 5V supply to ground, that caused APPS codes too.

sammy340

AlpineRAM,

Thanks for the help. I confirmed today that it was a APPS as I changed it out with an old one I had laying around and the truck started up and ran ok. The old APPS still has the bucking issue, which is why I changed it many years ago.

I'm looking for some feedback on the Timbo APPS as I'm thinking about ordering one of them as opposed to another stock APPS setup. Please let me know your thoughts, as well as anyone else who would like to chime in.

Thanks,

Jeff

AlpineRAM

I installed some Timbo APPS and some stockers.
Hands down, Timbo is better. First, you get the sensor without the cast bracket, you do not pay for the bracket, you just pay for a better sensor and the mounting instructions.
You will need a voltmeter and use this and the supplied paperclip to adjust the voltage.
The only thing I'd recommend is that you look at the shaft and the bushings before replacing the APPS, the sensor should not need to carry the load, the bushings should have virtually no play.

sammy340

AlpineRam,

Thanks for the help. I got the Timbo APPS installed yesterday and it works great. Feels like a new truck with the smooth accelerator now. I can't wait to try it out on a longer trip..........

Cheers,

Jeff

AlpineRAM

Thanks for the feedback!

jefe4x4

jefe here. I threw a PO121 code last week in Iowa on a 5-week trip with our 2001.5 Dodge 2500 Cummins HO, NV5600; California version. I pulled into a rest area and pulled out my code reader to find out why we had a surging engine and what code had just popped the check engine light. Down the highway we got to a RAM truck dealer and they hooked up their machine ( I think a DRB-2) to find it was the the APP sensor. The voltage readings did not line up or were shorted. They replaced and calibrated the new APP sensor. Another day and $1200 passed and we are 250 miles farther down the road (using my cruise control) when the truck made a sudden jerk and then dead pedal. I pushed in the clutch with an idling truck and over to the side. I sat there for a few seconds and turned the engine off. Trying to restart It would only idle.: no pedal response at all. Then calls to the last RAM truck mechanic who said it may be the wiring or in a worst case scenario, a dead ECM. He said a replacement ECM for a CAlifornia 6 speed HO Cummins would be impossible to find. Some time passed and a tow truck was ready to tow me 100 miles to another RAM dealer who said he would take a look. In the meantime, I started the truck and it seemed fine. The ECM had reset. Another dealer came into the picture and he said a lot of '01-02, HO, 6 speeds were getting this code. I took the cover off to see if the ball joint had popped off or the plug was not secure. The dealer dialectric greased the plug and bid me good luck. We then drove 1500 miles home to CA without incident. But my confidence in the truck is now shattered. It just turned 180K miles today.
*What do i need to do now to make this truck well again? I've never worried about the Cummins since we bought it new in 2001. We never had any problems with it. The only non-stock thing I have on the engine is a longer rubber tube on the waste gate to engage the turbo at a lower rpm. I do know that the ECM is engine specific: deturned or HO, trans specific: auto/5 speed/6speed, 49 state/California specific, all having different flashes.
The dead pedal happened each time while I was using cruise control, so I stopped using cruise control and the symptoms went away, mostly. I did get a couple episodes where the surge was back so I pressed down on the accelerator pedal to a higher rpm and it straightened out. Could there be any correlation between the cruise control and the APP symptom, since they both are wired to the accelerator pedal? Or maybe bad fuel or an injector woe? My wife is ready to roll the truck into a hole.
Thanks for any advice. I really appreciate the relative simplicity of the GEN II HO Cummins/6 speed manual and hope to have it around a while. I bought the truck new when the engine was retuned to match the NV 5600 and a few other drivetrain goodies came on the scene, enough to believe the truck would outlive me. So far so good.
jeff

AlpineRAM

Well, sorry to have to say this- dead pedal and surging points towards an injection pump problem.

There are other causes for this too, like insufficient fuel pressure, aerated fuel, electrical contact problems etc, but in many cases it's the pump. (Ouch $$$$)

I'd start with the excellent VP44 diagnosis guide by bluechip
https://www.bluechipdiesel.com/troubleshooting-1

Good Luck!