I have a no start problem. I narrowed it down to the ecm not sending power to the relay to turn on the vp44. Truck runs fine with the relay bypassed. I assume the ecm needs input from sensors before it allows the relay to be activated.

what sensor(s) if any should i check. I am guessing the cam position sensor?

 

You might check the VP44 diagnostics on www.bluechipdiesel.com or give them a call. I've read they are very helpful if you call them.

 

I think that the VP44 diagnostics is not of interest in this case.
It would be helpful if we knew exactly which vehicle we are dealing with- but preliminarily- if the computer does not send a signal there are two possibilities-
A: Not all conditions to send the signal are met ( maybe a readout of the computer is possible)
B: The computer is defective.

 

2003 F750 Ford with vp44 cummins
Needs a special medium duty code reader to scan the computer......which no average person has

 

What did you figure out? Have a similar problem.