-hey guys, gotta customers truck here with a problem
98 3500 auto 4x4 12 valve
trans pulls off in 2nd (like its in limp)-but no codes present
on scan tool trans relay turns off after intial key on cycle
also tach is not working-there is also no rpm shown on the scan tool either
any help would be appritiated!

 

-update
i found that the asd relay is also losing its signal from the pcm to keep it powered up
if i apply 12 volts directly to the 87 terminal of the relay, the transmission relay stays powered up and the transmission shifts perfect but the tach still dosent work
also a/c dosent work
im starting to think there is somthing goin on withe the pcm

 

Check your crankshaft sensor or wiring on the front.

You likely do not have AC or Cruise as well. The truck doesn't know it is running without a RPM signal.

 

well- you sir are the man!
-replaced crankshaft sensor on the front of the engine and everything worked perfect. I didnt think it would run if the sensor was bad, but it did!
thank you again
I owe you a beer!

 

LOL, remember this about the 12 valve, all she needs is fuel and air........ We don't need no stinking computer....