HELP When it starts quits imediately after, gages dead.

[NYFlapjack2]

I own a 2006 97x and I maintain my son's 2008 97x both 6 cyls.
The trouble is with the 100,000mile 2008, it's quit in a parking lot 15 miles from us, just went to go home from work and started but didn't stay running.
Otherwise everything normal no real indication that something was going to fail.
it needs about 5 minutes between restarts for something to "reset?".

I have used the forum searches and tried many items, thank you all so much for helping me zero in on this.
When you wait a few it will start tachometer moves but engine is shut down in 10 seconds or so.
Battery is under 1 year old and when it cranks and starts no lights dimming and it whips over fast, fires right up.
Just auto shuts down few seconds later.

With Key switch in acc or run position you do not see any dash gage movement, no PRNDL indication, no power door locks working etc.
With Key switch in run and start mode the dash indicators appear as normal (CEL, Brake, Stabill track etc), but again none of the above.

By removing the shifter handle & boot and with a fine wire probe you can access the key switch wires.
I can certify that .... it is not the same key switch, has more wires as the others (ie. TB).
I have a new extra (wrong) now, make some one on here a sweet deal!
Red is 12V, Orange is 12V in run, yellow* 12V start, white 12V acc, Brown 12V acc & run, pink* 12V run start.
* there are 2 yellows and pinks...yellow wire slot 11 no joy? 2nd pink I didn't record.....DOPH...

Under hood it doesn't appear to be a fuses. After the 36, 34, 22, 17, I pulled out just about all of them checked with continuity VOM tester.
Including the J case ones.
I also replaced the starter relay #47 with a new one.
I moved around the other relays swapping them in cavities to try too.
The 125A mega fuse has 12V on both sides of it and the main rear BMC large red wires also 12V.

Also at the under rear seat fuse block I did the same as above paragraph, fuse check relay exchanges.

Also I unseated the 3 PCM connections they are spotless and reseated then twice for giggles...no joy.


Any other ideas?

Can I remove the PCM for less tuned PCM from my 2006, plug and play in the 2008 safely for trial?
.... will it need a security learn in the 2008? and then back into the 2006? (EDIT: guessing no.. did more STFF and fleabay photos learning they look close but I see it appears that in 2008 there was a change on the PCM across the platform &1 plug is different... arghhhhh)

While I searched and read about fuel pumps, this fires up when it wants very well, and given no dash cooperation, seems electrical?
But what is the best way to "hear" the fuel pump as initial key on?

I have no idea if it is out of gas (they say it was low) but again no dash gages or door locks..sounds electrical.

Darned but it doesn't appear to be the low hanging fruit or I accidentally stepped into it yet.......

 

[The_Roadie]

I'd suspect the ignition switch guts because of the dash behavior, but as you discovered, they're unique. And I've never seen a schematic. COuld be a data bus communication issue, since the power locks require a working data bus. Any of a dozen intelligent modules could be jabbering on the bus and disrupt communication that would trip the security shutoff. If swapping the ignition switch guts for the right one doesn't work, I think you're going to need a professional (hopefully competent independent) with a Tech II tool to talk to the modules on the bus. Or find a GM dealer who realizes your vehicle is a trailblazer except for the ignition switch and a collection of merely cosmetic bits.

 

[NYFlapjack2]

So what ...electrical signal stuff does the connector at the negative terminal do? see photo.

The deal is .... As you mentioned a comm error type fault. I have played some with my other auto with fault codes too. (Mercedes and have Carsoft & computer ... Talk about complicated, gezzzz). Anyhow I thought WTH reset by dropping off the power? Haven't tried disconnecting the battery so I set out to do that...... When I did I swear this plug in the photo was weakly seated at best. I mean it shouldn't pulled out as I pulled the neg away from the battery right?

Reseated that locked it, imediately hooked back neg and bingo all systems 100%. I need son home from work now to road test more. Will follow up & advise later.

BTW, does the GM system (guess tech tool reader needed, not OBDII stuff just like the the Mercedes needing special factory or a Carsoft clone knocknoff) store all past faults like the Mercedes? On the Mercedes if I were to scan it after an incident like this I would see a comm error as well a BCM or SRS or ? What ever was triggered and so on in its history until I clear it.

 

[The_Roadie]

Mine is 2004, and I don't have that item. Not sure if it's a later-year-related upgrade, or a Saab-only customization to support something else you have that we don't. Sorry. (I HATE not knowing about a system like that, though.)

 

[NYFlapjack2]

So what ever that plug bonded on the negative main battery cable, and it's coil/loop around the large gauge wire (like a clamp on amp meter would do)...on the 2008 SAAB 97x is ...... it is not present on the 2006 SAAB 97x.
Per attached shot of the 2006 I just took.

Anyhow on the 2008 that plug definitely was not seated well as I discovered when un-hooking the battery.

After the fix and numerous tries yesterday, we've used it for all errands last night and today...at least a dozen more starts & stops.
No hint of any issue prior or ongoing.
Thanks forum we certainly saved a tow bill and gosh knows what else prematurely replaced.

 

[McGMT]

Mine is 2004, and I don't have that item. Not sure if it's a later-year-related upgrade, or a Saab-only customization to support something else you have that we don't. Sorry. (I HATE not knowing about a system like that, though.)

I have seen those stuck on to the cable on some of the full sizes, I believe it is just some kind of aux. voltage metering. Only a guess tho.

EDIT: Battery current sensor....

 

[NYFlapjack2]

Yup looked like a current flow measurement device, and it appears to be an Electrical Power Management (EPM) System that was later added.
GM claims it helps maintain a battery better and offers better mpg too.
Wonder if it being weakly plugged in with most or just some of the pins not contacting, or intermittent.. would have caused my start-shut off issue?
Certianly appears that way....It is mentioned in the owner manual I found on line (2007 TB anyhow). I also found a decent forum explanation of the EPM here:
The Electrical Power Management (EPM) System Description and Operation - TBSSOWNERS.com Forums - The #1 TrailblazerSS Dedicated Owners Forum