Truck Repair: cummins, thx chris, isx

Question
thx 1999 dodge 5.9 cummins, by the way the tach goes dead while it acts up,then when warm no problems. i think it may be the map sensor but i don't know,thx ,chris-------------------------
Followup To
Question -
the ck. eng. light comes on at start-up. the truck has no power and idles a little rough.  when the truck gets to normal operating temp.(190) it comes back to life..power comes back and idles fine.  thx a bunch. chris,1999 2500cummins.
Answer -
What make truck?What engine?(5.9,8.3,L-10,M-11,N-14,ISX)That way I might can tell you how to get the fault code from it.

Answer
If the tach is going out,it might be the engine speed sensor.It is located on the fuel pump side of the engine under the transfer pump in the side of the block.I would CALL Dodge for the price then call a Cummins dealer for a price of  a new one.There is only one bolt in a retaining bracket that secures it in the block.