[rickygasser]

Hey guys,
I've got a friend having some trouble with his 98 2500 with a Cummins. Here is his problem. When downshifting (manual tranny), the engine will sometimes shut down. When he realizes it's shut down, he pops the clutch and the motor fires right back up. This is alos accompanied by some codes, P0121 and P0234. One is realated to the wastegate not functioning and the other has to do with the map and TPS not communicated properly. Does this mean that on a downshift, the manifold pressure gets too high because of a malfunctioning wastegate and the engine shuts it self down? I don't know anything about Cummins so any help would be appreciated
Thank you

 

[gcrowell]

I'm assuming that you're talking about a 98.5 24 valve since you mentioned the TPS codes.

I had something similar on my 98.5 24 valve. Mine would flash the check engine light on me and just die while going down the road. If I turned the key off then back on it would fire right up again like nothing happened. It was a pain in the ass to diagnose because it kept self clearing the codes on me. One day it did it when I was near the diesel shop so I just wheeled in and had the guy hook up his code reader. I don't know the code it gave him, but he said it was the throttle position sensor. It's a dealership only item so I had to shell out $400+ for it, but it fixed the problem.

 

[rickygasser]

Thanks for the response. Did you have the same symptoms? could you find out the codes? When we erase the codes, they only come back after it stalls. I'll check for the price up here for the sensor Thanks again

 

[v8440]

From what I've read, the sensor can usually be cleaned with brake cleaner or electrical contact cleaner (what I'd recommend). If not, I can say I've never heard anyone talking about it costing $400, so I bet there's an aftermarket source. I'm sorry I can't be more specific than that, but I'd hate to see you go pay that much money if one can be gotten much cheaper. I bet some of the guys on the dodge sites with automatics could tell you.

 

[BigDaddyT]

Kinda sounds like a false reading from 3 different sensors. Might be a more serious issue. Stalling is also a symptom of low fuel pressure or insufficient flow volume.

The intake air temp sensor was the one we cleaned with brake clean. There is a way to reset the tps using key ons and such but I never had to do it so dont rememeber how it was done.

The dealer only item might be available at cummins if you call them. I bought all my parts from cummins because the dealer had a 300% over retail sticker on their parts. I never needed a tps but seems it would be part of the engine so it would be sold from the cummins shop also. I was chasing a ghost and replaced all the sensors one time(except the tps). They arent very expensive. Think it was about 180 bucks for the map, iat, crank sensor and the coolant temp sensor. Not sure which one it was but the problem resolved after I installed them.

 

[rickygasser]

The truck is a manual shift. I will trty cleaning the contacts on the TPS. The truck only stalls when downshifting.

 

[BigDaddyT]

I had mine reflashed many many moons ago to deal with stalling on low cetane diesel fuel.