94heritage

I need a little help figuring out a few things on an 02 suburban swap we are doing at work. A customer brings us a fairly nice 02 burban and wants to take the 6.0 out and put a 12 valve cummins in for better reliability and better mpg. I tried up and down to explain to this guy that you dont get much more reliable than an ls engine but he wasnt having it. Anyways we have the engine in and running all hooked up to the stock 4l80e but we are having some issues with the dash and i am not getting an rpm signal to the factory ecm. The tach in the dash works and reads properly, my volts, oil psi, and water temp all work great as well. The weird problem i am having is with the key on engine off the fuel level and prndl all work fine but once the engine is running the fuel level goes to e and the prndl goes blank. The conversion kit we used has a tone wheel that attaches to the damper and reads rpm off of a 2 wire tach sensor basically signal and ground no voltage is fed to it. My thinking is that the pcm isnt reading rpm because it doesnt see power ground and signal from the crank sensor but the dash reads it because it just gets a signal from the other sensor. Am i on the right track or am i totally off here? Im thinking the prndl goes out because of no rpm from the pcm but the fuel gauge confuses me because it works right key on engine off and doesnt drop until the truck is running. I have gone through all my wiring to make sure that we didnt remove anything that wasnt needed. Any help is appreciated because I am pulling my hair out on this thing.

94heritage

So i took a crank sensor out of one of my spare engines made a bracket and wired it up. It works and reads as it should but fuel gauge and prndl go blank. If you move the sensor away from the tone wheel so that it doesnt see rpm they stay on. I still have no rpm signal logging it. What is going on here?

rpturbo

iTrader: (47)

I am no electrical genius here by any means,so take all of this with a grain of salt, but to me, it sounds like you have a ground issue, and it's probably back feeding. This again, is just a guess.