2004 dodge diesle

i have done a couple of these trucks and have not been able to find proper tach signals .  I have tried using the injectors.  crank sensor.  inside the alternator at the rectifire. crank sensor works the best but sometimes undercranks. using the wire in the alternator works but when truck is really cold  it overcranks..  there is no longer a bcm in passanger engine compartment.  any ideas??

what we've had excellent luck with is using a tach generator.  It straps onto the side of the alternator and "feels" the rectifiers powering up (senses AC voltage), and provides a steady AC signal to use for tach.  Works EXCELLENT, and we insist on using it on all diesels.  Lots of shops like "tachless" settings, but this tends to overcrank when warm and undercrank when cold (its crap!)  The part number we use is TGEN, widely available from most shop vendors.

b

on the 2003+ Dodge Diesel trucks, the TCC (Transmision control computer) still lurks on the passenfer side of the firewall as it always has (Auto tranny only).  Tach is to be had there on the BLACK/ grey.... don't remember exactly which plug, but I do believe it's the only one in the harnesses.  Stil a 4 cyl. pulse count too. 

The standards, I believe, live at the ECM bolted to the driver's side of the engine block.....waaayy down.  don't remember the exact wire color or position at the moment.

Hope this helps.