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tlayne

2001 Cummins *HELP*

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tlayne

I have a 2001 3500 4x4 5 speed with 4:10 rear end. The only aftermarket parts this truck has are as follows- flo pro 4" turbo back, S&B intake manifold, S&B cold air intake, Edge EZ, and Edge insight CTS2 (truck had the EZ when I bought it.). Here are my symptoms...The truck will de-fuel while driving down the road, BUT ONLY IN 5TH GEAR. The problem does not seem to be RPM related because I can fuel all the way up to 2800 (or whatever it is) in 1-4th gear. The truck has absolutely no hesitation to crank, or supply fuel in gears 1-4. The only consistency with the issue is it seems to happen after the truck has been driven for 30 minutes or so and only de-fuels in 5th gear. When I crank it and drive to work in the morning it will run 70 in 5th gear no problems just like it is supposed to. However on the way home if I have errands to run after getting off it will not fuel past 2000-ish rpms *ONLY IN 5TH GEAR* (right around 50-60mph), literally if im feeling ballsy enough I can go faster in 4th gear than I can 5th. The truck is also not throwing a code. I have had these symptoms for a couple of weeks now and it has never happened in any other gear besides 5th. I have put a new APPS, as well as a new lift pump on the truck and it has not fixed it. I have a MAP sensor on the way hoping that maybe my problem is boost related. Everything that I have read about vp44 issues and ECM issues leads me to believe that the problem would be consistent with rpm's regardless of gear, as well as issues with getting the truck started? Has anyone ever had any issues similiar? Any ideas what this might be before I get into the expensive parts?

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Me78569

so you tested being able to do 75 in 4th?   it doesn't have a mph limiter in any other gear?

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tlayne

No I can run about 55 in 4th gear which is up in that 2700-2800 rpm mark. When the truck is acting up, sometimes it will not fuel past 50 in 5th which is about 1800-2000 rpm range

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Me78569

have you looked at / replaced the VSS sensor on the trans?

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tlayne

No I haven't. What exactly does that sensor have to do with fueling just out of curiosity. However now that you say that, on my insight sometimes it will read that I'm going like 130 and then jump back down to my true speed

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Me78569

that sensor can cause the pcm to send a defuel command.  

 

Someone else had a similar issue recently.

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tlayne

Ok. I'll put one on it this evening and see what it does.

Where can I find that thread? Or can you post a link in here? @Me78569

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Me78569

...I hardly remember what I told you 5 minutes ago haha.  

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Dieselfuture

Man Nick you put these threads to end like a pro you are. :thumb1:, just couldn't resist. 

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tlayne

Just put a new MAP sensor on it and so far that seems to be what the problem was. I bought a genuine cummins sensor to put on it, and the sensor I pulled off did not look at all like it (required 1-1/4 socket vs. cummins 1-1/16) which leads me to believe that sensor was aftermarket and had failed. 

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Dieselfuture

Did your new sensor come with an adapter plug, or plug on both sensors was same just different socket size. Still kinda weird why map sensor will only do it in 5th, unless you didn't get as much boost 1 through 4 and in 5th you can get more boost and it's over what ecm wants to see and it defuels. Mabe boost fooled in edge is not working correctly. 

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tlayne

Plug was the same size, just different socket sizes. 5th is definitely when I see the highest overall MAP's according to my insight. The rpm range where it liked to act up in 5th though is right about when it starts spooling up. My boost pressures in 3rd and 4th at my shift points are the same as what I normally see in 5th, but I guess since there is less load on the motor in 3rd and 4th it would fuel

Edited by tlayne

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Dieselfuture

Hopefully that's all it was, having electrical gremlins is no fun

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dripley

My original on the 02 was a 1 1/4 socket but they dont make that on anymore. The new is a 1 1/16 socket but the plugs are different. I have adapter on mine. Had it for years.

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tlayne

Well fellas, the problem is back with the exact same symptoms. The new MAP sensor fixed the problem for all of about 2 weeks. Where would yall turn now? Maybe a short in the wiring harness somewhere?

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Me78569

Did you replace the vss sensor?

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tlayne

No. After I put the MAP on and the symptoms went away I assumed the problem to be fixed. If it was the vss would the speedo still work?

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Me78569

Vss doesn't control the speed.  Vss is what the pcm and ecm use to defuel

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tlayne

The vss is the one located on top of the transfer case/transmission?

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Me78569
50 minutes ago, jlbayes said:

No, rear axle.

theres one on the trans as well that the pcm looks at for things.

 

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jlbayes
1 hour ago, Me78569 said:

theres one on the trans as well that the pcm looks at for things.

 

 

That is not vss. That is oss.

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Me78569

tps apps vss oss 

 

 

:shifty:  

 

lol  you are right

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jlongjohn

Where is the one on the rear axle? Same on Auto vs Manual? I replaced the one on my trans, I was having a similar issue. It does it less frequently now but only does it after a long drive and seems to be when it is hot (outside air temp and vehicle temp). Usually if I let off it for a bit or cool down like on a long downhill it seems to come back. 

 

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tlayne

@jlongjohn what all have you replaced? Mine only starts acting up when it is hot as well. Temperature and 5th gear seem to be the only common ground for my symptoms.  

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