Engine/Transmission (1998.5 - 2002) RPM Flux...

[BoeingDiesel]

First thing to mention is that I'm a ' New Member, and thank you TDR and members for this site. .



I bought my '99 new of the lot and have put over 130000 trouble free ( less brake jobs ),miles on the truck.

I have always maintaned the truck as per Dodge specs, and changed fluids always ahead of time. But, a

couple of weeks ago I noticed that @50-65mph the tach was intermitenly bouncing up and down from 50-75 rpms.

I couldn't tell if the truck was actually cutting out as our So. Cal highways are like washboards so I'm constantly

getting alot of bounce from the road. Also, I'm not getting a steady rpm increase from a dead stop to say 65-mph.

A friend of mine suggested that I check out the TDR site.

I joined up and started reading the posts, re; transfer pumps,vp44, fuel modules, iat,map, ect, ckp sensors,etc.....

I replaced the transfer pump and filter but no change in the truck, plus it just doesn't seem to have as much power

as it used to. I took the truck back to Dodge and they said it's fine, no codes, no problems, operating within specs.

I probably should mention that there was about 133000 miles on the truck when I replaced the transfer pump, but

always replaced the fuel filter every 5000 miles. Any suggestions, thoughts would be greatly appreciated and thanks TDR members.

 

[MCharlebois]

need more info-fill out your profile

 

[Wiredawg]

Really Tough, but...

Need more info about your rig. Sounds possible you could have a crankshaft position sensor problem. You get your Tach signal from it and your ECM goes into limp mode when it loses it. Been a while agao, so I don't remember if mine set a code or not.



Buy a Cummins manual: Big help in doing this type of trouble shooting. Costs about $75.



Wiredawg

 

[BLucia]

I have a 2001 2500 4x4 quad cab with 53,000 miles that i use to pull a 30' race car trailer. This truck has been great to me untill a recent problem with my tach gauge intermittenly going on and off as i drive down the road with no load on it. The truck continues to runs when the tach falls to 0 RMP but with a big loss of power and boost from the turbo. I called a local Cummins dealer and the guy told me to try replacing the vehicle speed sensor. So I did, but that didn't solve my problem. The next day the tach once again fell to 0 RPM on my way to work. If anyone has had this happen or knows what could cause this problem please write back. Also I was wondering what sensor actually drives the tachometer?

 

[JR2]

Different sensors...same problem.

I belive you both have the same problem, with different sensors.



On the 98. 5-00 trucks the rpm signal comes from the camshaft positon sensor.

On the 01 and up trucks it comes from the crank shaft position sensor.



Here is a good set of instructions on how to replace the crank shaft sensor.



Here is a drawing of the side of the engine. I belive the Crank sensor is #10. I also think the cam sensor is #11



#ad




The Mopar part number for the crank sensor is 05015488AA

The Cummins part numbers are 4002066 or 4002064 I don't know the difference but when I go to cummins I take the serial number off the engine data plate with me and they can tell me exactly what I need.

The Cummins parts will be cheaper than Mopar and if you buy them from mopar they come in a cummins box.



Here is a link to a search on the TDR for Cam Shaft Position Sensor



and here is a link to a search for the Crank sensor.



All this info can be found on Dave Fritz's Web Site Dave's site it awesome.





Welcome to the TDR to both of you and good luck with your problems.



JR2

 

[BoeingDiesel]

Thought that my truck profile would auto attach to my thread, guess not.

I have a 99 2500 SLT QC Auto 2-wd

K&N . A basic stock truck.



Something strange has happened in the last two days tho',, the truck has relieved itself of all the symptoms Idescribed and is running perfect. Something I probably should have mentioned is that thru all of this my MPG has gone from a avg. of 19. 4 to a solid 21. 5 mpg. Is it possible that the rig is running to lean a mix?

Well anyhow, thanks for all of your info and I'll post the results after replacing

all of the senors. .

 

[RustyJC]

My truck has had some "tach bounce" (+/- 25-50 RPM or so) since the day I took delivery. It hasn't gotten any better or any worse in 18K miles.



I suspect the culprit is the digital logic that takes the speed signal from the CANbus and converts it to an analog gauge display. It looks like the tachometer is "rounding" the digital RPM signal to the nearest 25 RPM, so the needle will bounce back and forth with any minor engine speed variations.



Rusty