Having issues with crankcase pressure, I have a 2009 American Coach American Allegiance 42G with a ISL400 I don't see the crankcase pressure in the list. Is there a way to get this information so I can monitor it?

Submitted by Art on Mon, 2020-04-20 12:00


From a (Guage) monitoring perspective, the VMSpc unit can capture PGNs (engine messages) for the various sensor packages mounted on the many brands & models of engines. If there is a sensor on the drivetrain--and it's even a little helpful to see it, we'll try to capture it. This pertains to variable outputs ie pressures and temperatures.

That said, Large diesels don't have a 'varying' crankcase pressure message for this sensor though the sensor does have a variable output. My limited understanding of the physics leads me to believe that it's a similar situation as the Lift Pump:

1. Both have an ECU message (a triggered-output) when the [very bad] condition is met. [ie No Lift pressure (Lift) or hi-pressure/ 3.25psi/20+" water (crankcase)]

2. Neither will output anything for normal conditions ie. Nothing to see here, move along.

Your question spurred me to do a little reading on this. It would be REALLY helpful alrighty to see a variable crankcase pressure as a way to understand air filter flow over time. And to understand that is to better prevent a dusting or outright rebuild due to clogged filters--whether intake' or crankcase filter. It seems the filter-minder may...or may not be an accurate guide for what that's worth.

When the engine throws a code, all are captured. So, on the one hand, there isn't a way currently to just 'listen' for the message via a gauge. However, nothing is lost as, even if we could 'listen' for it, using a gauge, it would light at the same moment your engine shut down and a error is thrown. The error event.

If it's any consolation, when we eventually get v5 of the VMSpc software out the door, it's designated to have arbitrary PGN-adds. This is a new trick where you set the PGN yourself. Whether lift pump or crank-case sensor, you can set a gauge to wait for it and show the outcome. No telling what you'd find however.

For your edification, I've attached a breakout from the Fault-Codes list:


I hope this helps



Silverleaf Electronics