01 Dodge Cummins tach issue

[Brandon39]

Hi this is my first time posting. I got a 01 quadcab cummins from my girlfriends grandfather that passed away . It has the h.o. motor and a 6 speed standard.  Back in 08 he put a new motor in and had problems with the tach ever since. Now that i have the truck i had it idling with my scanner plugged in and the tach says its idling at 500 rpm. The scanner says 800 rpms. When the scanner is reading 3000 rpms the tach says 2000 rpms. Other than that it runs good . Any help or ideas would be appreciated. Also my redline on my tach is at 3000 rpm which is odd because every other cluster ive seen is around 3300-3400 

[Mopar1973Man]

Any error codes present?

 

Did you check the cluster connectors in the dash?

 

Is it the right cluster? As far as I know the 1998.5 to 2002 is always been a 3,200 RPM redline.

 

Did you do a cluster test? Hold the trip button down and turn the ignition on, then release after the CHECK message. 

Edited July 31, 2021 by Mopar1973Man

[Brandon39]

Thank you for replying ,the only code that came up was for the grid heaters. 

 

Yes i pulled the cluster out and everything looked clean. I didnt see anything wrong with it. 

 

Im not sure if its the right cluster. As far as i know its the original cluster. I can attach a picture of it. I did the cluster test with the trip button and everything came out ok. The truck is idling in the picture

[Silverwolf2691]

@Brandon39, do you know what computer [not computer, engine] went in? Because i know there are compatibility issues within some of the model years. Its 00 and down and 01 and up..

 

 

Edited July 31, 2021 by Silverwolf2691

[Brandon39]

I believe he used the ecm off the old motor. Theres the id tag on the gear case with build date 4 27 2000, but i imagine that gearcase came off the old motor right? I did the cluster test again and when all the dash lights come on the wait to start light didnt illuminate. Also found a number 58 stamped on each side of the block and i didn't think there was a 58 block 

[Silverwolf2691]

Meant engine not computer.. the tach/computer uses different methods to get rpm between 00 and 01.. depending on the extent of the engine swap that happened, whether it was a block only or full engine, might be causing issues. 

 

After rereading that article, I dont know what the sympoms are for the swap.. I'd imagine just straight up not running, but i dont know. Might have sent you down the wrong rabbit hole..

[Brandon39]

I was told he just bought a reman long block and switched everything from the old motor to the new motor. How would i be able to tell what year the replacement block and internals are? Also since my scanner reads the right rpms wouldnt that mean my cam gear and cam sensor are right or does the obd port read rpm from another source also like the injection pump? 

[Silverwolf2691]

That im not sure of, in regards to the obd vs tach.

 

But the 3k red line vs 3200 redline might have something to do with it.

 

I did some digging on google images, i found one 2000 cummins that had a 3k redline. Was a wood grain dash truck. Otherwise its 12 valves and common rails.

 

 

[Brandon39]

I figured out my instrument cluster is bad. I swapped in a different one and my rpms were spot on 

[dripley]

Good to hear.