CM871: lost boost

[RMezaJr]

I was on Interstate 5 Southbound, going up the grapevine when my boost gauge dropped to 0 and started hearing a hissing sound. The check engine light came on, don't remember if it came on during or after I noticed the boost gauge. Pulled off to the side and looked for anything that looked out of the ordinary, everything looked fine. I would only hear hissing while in motion so I assumed the gauge was powered by air, my tanks remained at capacity and at that point the engine brakes still worked. When the hissing stopped, the engine brakes stopped working. I got the following error codes but seem to be inactive.





What could have caused this? Is this a safety measure from overboost?

[tree98]

Sounds like a boost leak, maybe a boot popped. You can find whatever is leaking by Pressurizing the entire engine. You'll need to block off both sides of the turbo and put 30 psi of shop air in through the cold side.

[Rawze]

It being a CM871, give the EGR pipe on the intake side a good yank. The pipe that connects the top of the EGR valve going up towards the intake. - Those things are notorious for rotting out over the years where they meet the top of the egr valve, then popping loose like that in a hard pull.

[RMezaJr]

Well, I guess I'm blind. I checked the clamps and they all seemed fine. The boot popped off just past the first clamp after the CAC and I missed it. Thanks