I have a 1998.5 2500 that has an issue that just keeps getting worse. The problem is this: The truck normaly starts and runs great, but usually if I let the truck warm up for more than 15 minuts or so the engine will start reving on its own to various different rpms. Then if I go to start driving it the throttle pedal all of a sudden stops working meaning the engine drops down to iddel and the pedal doesnt do anything untill you pump it a bunch of times untill it reconizes it and then you start going again. meanwhile the check engine light will come on. I figured I wouldnt let it warm up any more and now it does it while I'm driving. i know when its going to happen because as I drive the engine will start to surge and you can see the rpms changing, then shortly after, engine drops to idel, check engine light comes on and I have to pump the pedal a bunch before it will start to go again. Its starting to do this more and more and becoming very dangerous becasue sometime it will do it when I cross traffic at an intersection and I stop accellerating for about 5 seconds untill the pedal starts working again. It does this under towing load or no load at unknown times. It's scary and needs to be fixed. I pulled the codes and got P0122 (tps, current low input), P0123(tps, current high input), P0121( tps MOD$15 CKT range/perf). I talk to some dealers and they cant say for sure what it is unless it does it while there working on it. They said it might be the tps sensor but I dont want to waste $400 on a new sensor unless I know for sure. If anybody knows anything about this please let me know! Thanks Jon

 

I bet its going to be your tps or apps (Accelerator Pedal Position Sensor).

 

I remembered a friend of mine worked at a dodge dealer. I went in and bought a new apps for about 200$ and that fixed the problem. I'm way happy thats what it was!

 

I would love a new truck but sometimes I am really glad I have an old mechanical monster!!

 

If it were me, i would get a new apps from Cummins. They are a lot cheaper and you don't need to do anything special to install it.

 

cummins didnt make the apps for the 98.5, it's a dealer only part from chrysler. trust me I avoid dealers as much as possible and contacted cummins first. I got a deal for 200$ compared to the normal 450$. Remember this is the apps, not the old style 45$ tps.

 

Yes you have a bad APPS. Check it for cct continunity on pins 1/2 off idle and 1/6 idle you should have less then <125 ohms contact resistance and over > 100 k open cct. find a cummins dealer and get the wiring daigram for your year of truck. This is for the 99 year should be the same. What it is doing is losing the signal to the ECM and then to the FPCM. Hope this helps.