2008 GMC Sierra misfire

has The active Fuel Management system I’m getting misfire counts on 1 4 6 7. I pulled valve covers off all rocker arms seem to be moving just fine. But on the scanner in data I’m getting circuit faults for all the solenoids. They say fault for short to ground open etc. anyone have ideas what to do next. I checked oil pressure it read 25 psi in cylinder deactivation data. Compression is 140 in all the deactivated cylinders.

I just had one that made good compression cranking but nothing while running. Removing the Schrader valve from my compression gauge only made it impossible to read, lol.
Start it up and let the pressure out of the gauge then see if it rebuilds.
On a non missing cylinder I was seeing 80-100psi, and on the misfiring cylinder #6, 0psi.
Even though it made 150psi cranking.

I also pulled the valve cover, all the rockers moved the valves and it passed a leak down test no problem

There's a TSB that states that the VLOM lifters can stop working as the engine fires up.

I had no solenoid circuit codes though, and that oil pressure sounds low...

I’m not getting solenoid codes either. Just thought it was weird seeing the circuit status pids as fault.

Oh, my mistake. I misread that.

Yea I seen that tsb as well seen the rockers moving. So basically pull the schrader valve from the compression tester? And let pressure out with release and see if it rebuilds?? What was the fix for yours?? This was an auction truck has all new injectors plug wires computer new cam crank sensor

Pulling the Schrader was not fruitful. I put it back in and let the pressure out of the gauge with the relief button and let it build pressure again witll running.

We advised a new/used engine rather then get married. If it was mine I'd attempt the lifters, but too much work to have it fail in a month and be on the hook.

Still waiting for the owner to decide...

I’m thinking that’s the issue but need to do a running compression test. I was thinking about it but seen the rockers moving so figured I might be on the wrong path. Hopefully I see 0 psi and can get it back to the used car guy let him mess with it

I hope that's enough to get it out of your hair. Good luck!

The map sensor voltage and vacuum reading looked solid on the scanner no oscillating or fluttering. I’ll let ya know how it goes!

I dealt with a misfire recently where it was a compression issue that did not show up with a mechanical gauge. I did about 15 seconds crank time and did a relative compression test. My waveform was perfect for random numbers of revolutions. An at Other random revolutions I had one low cylinder. For me it turned out to be a bent rod. Not saying that is your issue. However I learned that Mechanical compression gauges won’t show this type of fault and relative with a long crank time was the only way to go.