Fault 125 intake manifold 1 pressure

[Papa_Buck]

I got this fault code a couple of weeks ago and I have since fixed it. However, the problem was not what I originally thought. I am posting it here to possibly help others. (Rawze, this site is worth its weight in gold.)

I am running a 2017 isx 15 2350 with 20k hours and 900k miles

This fault first presented itself as an engine 25% derate, with NO check engine light. Just the message on the dash. After about 2 hours the message went away. When I got back to the yard I plugged into the engine and the nay fault was the 125 intake manifold pressure message. So I started looking for the leak in the rubbers, none. Next I pressured up the car, held with no loss. Cleared the code and waited for it to happen again. Next trip out, there it was again, 2 hours later the message cleared, but when it cleared it did trigger a check engine light that lasted about 3 hours then gone.

This gremlin kept showing itself like this for 3 weeks while I kept looking for air leaks. I did change the imap sensor in that three weeks but no love. Finally I noticed the pattern. When I was at sea level, and climbed up over 3000 feet, I would get the derate light 30 minutes after cresting. I called my Cummins part guy and asked if these engines had a barometric sensor somewhere. They do, it’s right in front of the imap sensor just attached to the harness, after changing it out, I have been fault free now for a week.

I hope this helps someone like this site has helped me.

Dave