No crank no start

[John Trail 06]

06 Chevy trailblazer 4.2 4/4
Code po601
In July 2018 went to start it nothing
I tried and tried nothing then it started with check engine light on.
Now no problems until this week 9/3 9/4 9/5 and to present.
Start it up runs for a few seconds then stalls and no crank no start I keep trying and trying then finally it starts.
I watched may03lt video and when I find someone to help me do the test and before I remove the relay it starts up. * I watched may03lt since I found it on YouTube and may03lt has helped me with other issues like Tran shift bushing*
I checked grounds on block, frame, and also locked for broken wires to computer and other connections. I also tried switching the relay with a new one from ac delco.
I pulled the cover off of the steering column and checked to see if I’m getting power out of the ignition switch ( I used wire diagram from moosemans manuals )
I have read that I may need a new pcm but if it is a pcm would it work sometimes then not. I do have means to a higher end scanner ( snap on Solus 13.4 ) I do have communication when it isn’t cranking or starting.
Thank you for your help

 

[Mooseman]

P0601 Internal Control Module Memory Checksum Error

Your PCM is toast. Pick one up at a pick-n-pull from a same year, engine and gearing and swap it in. Do a security relearn and you should be good to go.
PCM Security Relearn

If you have limited choices and can't get the same gearing as yours, you can use another with different gearing programmed PCM but your speedo will be off. If it annoys you, you can get it re-programmed by someone with a Tech 2 or at the dealer.

 

[John Trail 06]

P0601 Internal Control Module Memory Checksum Error

Your PCM is toast. Pick one up at a pick-n-pull from a same year and engine and swap it in. Do a security relearn and you should be good to go.
PCM Security Relearn[/QUOTE
Thank you for the quick info With the pcm being done it still does run sometimes. Wouldn’t the tb not run at all.

P0601 Internal Control Module Memory Checksum Error

Your PCM is toast. Pick one up at a pick-n-pull from a same year, engine and gearing and swap it in. Do a security relearn and you should be good to go.
PCM Security Relearn

If you have limited choices and can't get the same gearing as yours, you can use another with different gearing programmed PCM but your speedo will be off. If it annoys you, you can get it re-programmed by someone with a Tech 2 or at the dealer.

P0601 Internal Control Module Memory Checksum Error

Your PCM is toast. Pick one up at a pick-n-pull from a same year, engine and gearing and swap it in. Do a security relearn and you should be good to go.
PCM Security Relearn

If you have limited choices and can't get the same gearing as yours, you can use another with different gearing programmed PCM but your speedo will be off. If it annoys you, you can get it re-programmed by someone with a Tech 2 or at the dealer.

Do I have any other way of checking it before I get a new one.
Maybe wires to back probe or something like that?

 

[mrrsm]

You have some additional options to pick from on eBay and some of these Vendors-Sellers will even program the PCM with your VIN after the sale:

https://www.ebay.com/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=gm+4.2l+pcm&_sacat=0

Before you venture to any Salvage Yards... You could also pull the Three Main Connectors off of the present PCM and using only CRC Electrical Cleaner (...available at Autozone) spray out the connector innards and let them all dry very well B4 re-attachment. Also spray out the three submerged areas of the PCM as well and wait patiently until everything is Bone Dry. Don't use WD-40 or any Petroleum Oily Solvents in this application. IIANM... the (3) 10.9 High Quality Fasteners are either 7 or 8 MM...and the socket needs to make a good fit to loosen them. The three Olive Green Grommets need to be properly in place B4 being snugged up to the PCM.