2012 Chev Suburban 162K mikes … won’t start … normally …

… after 6 hour diagnostic time tech states computer is sending wrong codes to Powertrain relay.
Computer sending wrong codes to relay?? WTF!

Also .. tech states car cranks randomly in lot …. No reason …

they have tool to override relay … and car starts and runs just fine …until you turn it off … then no start.

recommend i take car to dealer to have computer reprogrammed…

so…does this sound reasonable? Anyone else in world run into this problem? Could there be another reason?

car is home … so I can’t start it … it will have to be towed unless I can figure out another option.

any direction would be greatly appreciated…

ben
monroe, Mich

6 hours and that'* what you get.....Run......fast and far.....run..

I agree: WTF.

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Sounds like a short somewhere to me. Bare copper, bad connection, something.

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There'* always a reason.

This tells me something wrong in the path between the ignition switch and BCM. While it is running, if the broken thing tries to command start again, it would be ignored. I good diagnostician would look for this to help diagnose better than whatever this is. It probably does it more often while running.

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​​​​​​​Reprogrammed to what?

"Hello dealership, please reprogram my computer so it doesn't randomly try to start itself."

Does this mechanic think that this is programmed into the PCM or something?

[randomlyTriggerStarter=Enable] . . . ??? LOL

No.

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Probably.

Yes.

Does it crank randomly in your driveway/garage/etc.?

If you're handy, get a relay bypass kit for $25.00 at Amazon. Now you can start your car. Take it to a mechanic that knows how to diagnose electrical issues.

Michigan. Rust. Corrosion. Misery for cars.

Get a manual, chase down every ground path and trace all wires. Also check the solenoid wires to/from the starter to wherever they go. Make sure it all looks good and fix what doesn't. I'd give 75% chance your problem would get solved just by doing this.

Too late for that.

Okay . . . ?

UPDATE: I ordered rebuilt ECM computer from EBay … installed in 5 minutes … Suburban started right up … no apparent issues.
Drove it around the block .. no problems.
So … Instructions from ECM vendor states I need to have the ECM programmed for fuel and timing. I found a local auto/transmission repair shop that says they can do the programming … $250 … $250 OUCH!.

So … car is running fine … what if I don’t do the programming? …. Will I regret that?

Not sure. I'd suggest you go ahead and do it. There could be little things missed like final drive ratio therefore shift points etc.

UPDATE: I installed replacement ECM computer bought on EBay .. easiest fix ever … car started right away…no apparent problems. Put over 150 miles on it .. 6 or 7 trips … everything worked great … until it didn’t. Now when I go a few miles and stop the engine … when I try to start again …NOTHING … ABSOLUTELY NOTHING… no clicks, no lights … nothing. I wait … pull some hair out of my head .. 5 minutes later … car starts fine … shorter trips don’t cause the problem…appears that 10 minutes/miles or more cause the problem.

I was previously informed that I need to have my replacement ECM reprogrammed … I investigated that and was given a $225 programming estimate. I balked .. since the car was running fine at the time … now I may need to reconsider.

Could this 5 to 10 minute loss in ignition response be associated with the ECM or could it be a heat related sensor issue?

Looking for someone who may have experience with this issue…ECM or other?

On another note … I still would like to have the ECM programmed. Is $225 a fair price? Any recommendations as to best place for price and service.

Confirming:

No lights on the dash?

No gauge sweeps or movement?

No dome lights?

No exterior lights?

I think this is a secondary concern. The primary concern needs to be fixed first. It sounds like $225.00 is the going rate in your area. I've heard of it for a little less, but not enough to quibble with considering the loss of use of your vehicle for months. Personally, I'd go to a dealership with a good reputation for this reprogramming, and while they're at it, they can at least looks ansee what the PCM thinks while one of these events is happening..

You get nothing when it don't work. No lights, clicks, nothing. Is that correct? If so, have you checked the ignition switch?