2003 Silverado 5.3 EVAP/ECM issues

Edit here: due to the suggestion of the topscan tool I got it and although it still had some anomalies in the data display sometimes... it did actually give me the ability to bidirectionally control the purge and vent solenoid so thanks for the suggestion for that. Still like the other tool for some reasons but the topscan isn't half bad.

I am going to try and keep this short because I have written it once already and it got erased. Long story short have a p0442 small evap leak and p0455 large evap leak. Was trying to use my 7111 innova scan tool to diagnose it and in the process of trying to command purge and vent valve on and off had some issues. When I try to open the bidirectional tools for either valve I am met with "no communication or not in test conditions". One time trying to load the test it stalled the engine. Another time trying to load the test it briefly gave me the increase or decrease percentage buttons for the purge valve but only for half a second and then gave the same error message as before. I am beyond confused. Another weird thing that's happening is while it is reading live data under OBD2 diagnostics such as RPM the data updates pretty fast but viewing the same data with OEM diagnostics under PCM live data it is substantially slower, only updating once every minute. Also tried with another scan tool and got the same results. Any help is appreciated 

Frustrating to lose a long post, the forum times you out automatically and you have no way to tell. I make a habit of copying my posts before I click submit now.
There are many factors that effect the data rate, I think must likely you have a tooling issue. Nothing against the Innova, I am just not surprised it isn't behind super helpful.
Certain trouble codes being set, certain data pods outside of limits line fuel tank volume, temperature etc. can restrict the use of the bidirectional controls.
If the scanner isn't any help, I would disconnect the electrical connector to the purge valve, and the line that goes from the purge valve to the tank, start the truck and with a vacuum gauge see if the purge valve is fully sealed as it should be.
I would like wise disconnect the vent valve electrical connector, supply power and ground with a battery and smoke the system to see if the vent valve can seal correctly.
That generation truck is notorious for vent valve issues and vent valve circuit issues. The white wire to vent valve breaks the conductor inside the insulation a few inches from the connector. A good pull usually reveals this.

I haven't used the Innova 7111, but I can say that the EVAP bidirectional tests (purge, vent, purge/seal) absolutely should work. Snap-On, Autel, Launch, TopDon, they almost always run those tests without issue.

First thing that comes to mind is a failed Fuel Tank Pressure sensor. If the sensor is falsely indicating excessive pressure or vacuum, the PCM will kick you out of bidirectional EVAP tests for component protection purposes. You can check for this with the key on, engine off and fuel tank cap removed. In OEM data, the FTP should read very near atmospheric pressure, or 1.5V.

As for the slow OEM data, I'm really surprised. OEM data on this generation of GM is usually fast enough to support 8-10 PIDs with a decent refresh rate. I see you tried another scan tool, but I'm still inclined to believe you have a scan tool problem.

I've used the TopDon TopScan on that year/make/model of truck to do EVAP testing with no issues. I understand if you're not thrilled about spending more money on scan tools.   But the TopScan is pretty affordable at less than $75, so the stakes are fairly low.

www.amazon.com/dp/B0C3QQYQ1B

I was wondering about the ftp sensor as well but oem data is questionable because of the odd update speed. I may just probe the wires to get a reading. And thanks for the suggestion of the scan tool the one I got was $600 so a $75 one wouldn't hurt to try if it's been proven to work for this before.

Thanks for the suggestions on alternative testing methods I will definitely try that and look at that wire

It sounds like communication issues with the vehicle’s ECU? If the problem persists, try resetting the ECU or check for software updates on the scanner for better bidirectional control.