Engine/Transmission (1998.5 - 2002) Autopsy of an APPS

[WOT]

Anyone know the part # / cost of an APPS in another ISB 24V application? Since it hooks directly to the ECM I would have to believe it would work (maybe with minor tweaking). If Cummins has one that physically looks the same & is relatively cheap < $50 I would be tempted to get it, apply the same voltages as go into the "dodge" version and see what the outputs are on it. If they are the same the bingo - done. If not then maybe have to add some resistors or to get it "right".



Thoughts?



FYI:

the connections to the ECM from the APPS:





APPS ECM

---- ---

1 >--------BK/LB--------< 11 (B+)

2 >--------LG/DB--------< 16 (Idle Val. Switch 2)

6 >--------BR/OR--------< 1 (Idle Val. Switch 1)

4 >--------BK/YL--------< 32 (APPS Sensor Ground)

3 >--------LB/BK--------< 25 (APPS Sensor Signal)

5 >--------DB/WT--------< 31 (APPS Sensor Supply)



I seem to be having a touchy throttle at a certain position (surging at that position). I am going to try to validate the problem by putting my meter on the sensor signal and see what it is doing when it surges. Sure wish I had an ODB tool to watch throttle value, but the meter will work.

 

[jrobinson2]

I cleaned one of these a little over a month ago and its still working. I sprayed a lot of contact cleaner in around the pivot point, turned the shaft back and forth with a screwdriver, dropped the thing on a concrete floor then blew it out with air. I doubt its air tight because quite a bit of contact cleaner came out when I blew the air in it. The problem with the truck was low power all the time and sometimes the throttle would would go dead like the accelerator was released, code set was P0121. I don't know what fixed it, simply removing and installing the electric connector, cleaning the APPS or dropping the stupid thing on the floor but the truck has run fine since I worked on it.

Jared

 

[Texas Diesel]

My truck goes in the body shop on Monday, we'll have a bunch to play with soon. Wish the body shop would take ME and do a little sanding and bondo work here and there

 

[Sticks]

WOT - Thanks for the wiring info!

 

[WOT]

Surging was really getting annoying... pulled the APPS to check it out. Sounds "scratchy" when you move the throttle in 1st 2/3 of travel & sounds smoother in last 1/3 - wasn't happy. Figured didn't have anything to lose, drilled a hole and cleaned with contact cleaner. Sounded a little less scratch, but not great. We'll see how it does when I put it back on. I sealed the hole with some silcone.



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[Gary - K7GLD]

Under "normal" circumstances - those where simple loss of good electrical contact between the rotating fingers and the resistance meterial were the cause of the problem, what was done up above SHOULD cure the problem - but if a serious design or assembly flaw creates the "digging/scraping" effect that then destroys the resistance material, then the squirt of cleaner will only provide temporary relief at best - and the REAL problem remains...



We'll know more when we get a few old replaced units to experiment with...

 

[Sticks]

WOT - Did it make an improvement?

 

[WOT]

don't think it worked

I got it back in and didn't drive it, but tried to hold the APPS in one position and the RPMs seemed to fluxuate so I don't think it did the trick. I pulled it back off and took some more pictures after disecting it a little further. If you look at the attached pictures, one set of brushes looks like the fingers sagged and might actually be contacting in 2 spots (not just the "rake" of the finger. The front fingers on the same picture are after I "tweaked" them to try and straighten them out (they were really sagging). The brushes second picture looks look really good. Also, I noticed there is a white "film" over the entire circuit board (for lack of a better word) where the resistive surfaces are. You can rub it off, but contact cleaner won't remove it.



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I'm beginning to think it's time to cough up some $$$ and get a new one. Once I do I want to get the resistance values after separating it from the circuit board - maybe similar to what's on the 1st gen?

 

[Gary - K7GLD]

So, in your opinion, the finger weren't really making solid contact with the board - and at least one finger was sagging and making contact at more than one point?



Nice closeups!

 

[WOT]

From what I could see that's what it looked like was happening at least on the brushes on the 1st picture. I tweaked both of them and put it back on and still get a fluctuating RMP when I try to hold the throttle in one position (about 200 rpm or so @ 1800). I wonder if both brushes looked like the 2nd if I would have had any problems. Could just be that the material just doesn't hold up and you wear through the resistive layer. I'm gonna drive around on it for a couple of days and see what happens, but most likely will just bend over and pick up a new one. Dang thing should not be that expensive!



Interestingly, I threw a p-1692 code during the process. Will have to reset that sometime I guess.

 

[Sticks]

Oh look, another one with the fingers pointing down scratching the crap out of the contact surface.



Would the white substance be from the first cleaning, residue from the cleaner?



I did some tinkering with the contact surface with my multimeter. Pin 4 to 5 is the resistance surface, and pins 4 to 6 is straight continuity irregardless of the brush position. I lost my brush wheel so I do not know how it is wired.

 

[WOT]

The white residue can't be from the contact cleaner, it looks like something that was brushed on. I also played with checking the resistance (From my pictures, each of the 2 brushes show a direct short, so I would assume they are connected within the brush wheel). I was getting about 2. 7K of resistance across the resistive material, but I can't stand by that number since it is still connected to the circuit & that might be altering the reading. We really need to disconnect the circuit board to get an accurate reading.



WOT

 

[Sticks]

Originally posted by WOT

The white residue can't be from the contact cleaner, it looks like something that was brushed on. I also played with checking the resistance (From my pictures, each of the 2 brushes show a direct short, so I would assume they are connected within the brush wheel). I was getting about 2. 7K of resistance across the resistive material, but I can't stand by that number since it is still connected to the circuit & that might be altering the reading. We really need to disconnect the circuit board to get an accurate reading.



WOT

Pin #'s 4, 5, & 6 go directly to the contact surface, and if I remember correctly, do not go to the circuit side. 1, 2, &3 go to the circuit first, then obviously to the contact surface.



The one that I butchered did not have any white coating.



I think my resistance was 2. 6?k on the 4, 5, 6. and the other being the direct short.

 

[WOT]

From the pin-outs in my service manual I would expect 3, 4, & 5 to be going directly to the resistive material.



Also, after working ok yesterday, I got in the truck today and had no response on the pedal Guess I will have to tear it apart further when I get a replacement. I could probably ding around with it some more, but I've already spent too much time fooling with the stupid thing!



WOT

 

[Sticks]

WOT - Yeah, aggravating isn't it.



I get three or four days in my truck that are real pleasant, then one day nothing but surging all day, at varying RPM's between 1500 - 2000, right where I am driving on the highway or the surface streets.



If we all stick with this, we will find a solution. We than you for your time and experiments. Keep us up to date on your findings.

 

[WOT]

FYI:



Cummins part # for the APPS on my 2000 was 3937162 which is superceded by 3949728 which is superceded by 3970085.



It's $336. 59 from Cummins. The dealer wanted $480

 

[Gary - K7GLD]

Makes ya wanna run right out and buy a dozen or so, don't it!



That is EXACTLY why a couple of us want to disassemble a few to experiment and see if there's a common failure point, and possible easy (reasonably!) fix to return one to service...

 

[Sticks]

Originally posted by WOT

FYI:



Cummins part # for the APPS on my 2000 was 3937162 which is superceded by 3949728 which is superceded by 3970085.



It's $336. 59 from Cummins. The dealer wanted $480

WOW! Cummins Rocky Mountain said that they don't have any, and they can't get any. It is a dealer item only. They should be the same. I will take that part # to them and have them look it up.

 

[WOT]

I got ordered it from Cummins Northwest (Oregon). The local shop had to order one from the factory and would take up to 2 weeks unless I paid a 13% charge for next day. It was cheaper to ship 2nd day from OR and skip the sales tax (I'll have to remember to claim it on the taxes this year )

 

[Weidner]

apps problems

My apps is still hanging in there. I had no response a few months ago, but it came back on a re-start. It surges some and will lose all response on heavy throttle. We are heading on a trip from Minneapolis to Battle Creek MI this week, I hope I am not replacing this on the side of the road in the middle of the night. If I do replace it, or when I do I should say, I will have another doner for you guys.