All of a sudden my cummins attempts to shift up and down between third and fourth when cruising between 40 and 45 mph on level ground. The shifting problem, at least for the time being, is slight. The vehicle travel doesn't seem to be affected, and the only reason I notice it is that it makes the engine rev up and down (I can hear it and see it on my tac). The other puzzling thing is that most of the time the transmission seems normal. The odd shifting/revving seems to be more prevelant when the vehicle is cold, but then does it again intermittently well after the truck is warm. I checked the tranny fluid and the level is good and the fluid looks to be in good shape. Any ideas?

 

tps more than likley

 

My truck is a 98.5 24v with a VP44 injection pump. Does it have a tps?

 

tps is called the apps

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mine does the samething since i added wheels and tires. Mine is just locking and unlocking in od, maybe that is what urs is doing. Same speed as your at.

 

all most 100% sure its your APPS mine did the same for a wile untill i replaced the whole thing.
1st scan for coads
if you get a p0216 and i beleave there is 2 others related to the apps thats your proplem
2nd if you do get coads dont try to adjust it, it will only get worse, I know and have seen it on others so leave it be till the new one gets there
3rd the best price Iv ever found is at ROCK AUTO its under emishion controle and is made by Air Tex(a good company) there way cheaper than the stealerships

 

Thanks for the replies! Sounds like it is likely the apps. I guess I'll scan for codes!

 

CHECK FOR GROUNDS MAKE SURE ALL GROUNDS ARE CONNECTED AND IN GOOD SHAPE!!!! sorry for the caps but my 99 did the exact same thing and i got a tps for it and it didnt fix the problem and then i got one of them DTT noise filters and it fixed it for a little bit then it started again i eventually found one of my ground wires wasnt even hooked up. also run a wire from one of the studs holdin your computer to the firewall to the ground side of your pass. battery. these trucks its all about grounds and that will cause it everytime. my 99 would shift in and out of lock-up CHECK GROUNDS! then go from there and welcome to diesel bombers!

 

Thank you very much. I will definitely start with checking the grounds! Thanks again!

 

Also if you have a bad battery it may cause that as well. Friend's truck did the exact same thing you are describing and ended up one of the batteries was bad. Truck would fire up fine, just a little slow but it didn't happen overnight so he was just used to it and never thought anything of it.

 

Thanks all for replying. I scanned my truck and I am getting a P 122 code (tps, low voltage input). I found some additional info from another thread on troubleshooting this code (https://www.dieselbombers.com/24-val...ode-p0122.html). I think most likely I'll have to replace the apps. Will post again with the final result. Thanks again!!