Hello. Need some help. Fiancees outlook suddenly lost blinkers/high beams/ and lock unlock from inside car but works on fob. Hazard switch doesn't even work. Neither does Trac control/tow button/front sprayer but rear works. I checked all the fuses and switched around some relays and nothing. It does has an aftermarket radio but I even tried putting stock back in and that didn't work either. Had a buddy check with his fancy Matco scanner and he could control all of the above and they would work from his scanner. I'm assuming it might be the BCM but figured i would check here first since I seen you have to pay dealer to even program a new bcm. His scanner didn't find anything wrong either so kinda lost at this point. Thanks

 

Not quite sure how those tools work -- meaning do they send commands to the BCM that it carries out, or do they insert themselves into the CANbus communications bus and act as the equivalent of another BCM.
The difference is quite important as if the former is true, it sounds like the BCM is OK (maybe); if the latter is true, then it MAY indeed be the BCM. Awfully young for a BCM death.

Also, you said you checked all the fuses (assuming they were intact). Did you check to make sure you had 12V relative to chassis ground across the ones involved in this (one end or the other?)
Is it the original battery in there? Do the problems exist when the car is both running and not?
Just to rule out charging system problems, I would take your vehicle to Autozone or similar and get the charging system load tested for FREE to ensure your alternator is putting out full output. If it is not, the addl current required while the car is running gets pulled from the battery. Today's cars are extremely sensitive to supply voltage for the computer modules. It's a longshot but a good test to rule out that issue. And it costs you nothing.

 

Thanks for the reply. I forgot to mention I also thought battery as well so I put in a brand new batt and it didn't change. My buddy's scanner showed that alternator is working fine and charging correctly. This weekend when I have more time I'm gonna tear into it some more.

 

Is your buddy a mechanic? Can he get you electrical schematics?

 

Kinda lol he just started his own dealership and is extremely good with cars he actually told me to see if I can find a diagram. So that's something else I'm gonna look for before the weekend. Otherwise he has a friend with a junkyard and has one there we might just try swapping the bcm and see if his scanner can program it since it works on ecus.

 

He'd have to have the most recent firmware for the Outlook.
Plus you'd have to do a BCM relearn to get it to talk to the PCM and for the passlock system to allow the car to start

Or you could get mega lucky

 

Well I hope i do lol. Personally don't wanna pay upwards of $200 to have dealer program it. I'll post if find anything out thanks

 

Alright back with the fix. It was the bcm and thankfully my buddy's friend had the exact same year at his junkyard and the numbers on both bcms were the same so I swapped it and he had to calibrate the brake pedal and crankshaft sensor for some reason otherwise all is well and it only cost me $25 for the bcm. And yes he has a Matco scanner with the subscription for gmc. So you don't need a dealer just a decent scanner. Thanks

 

Happy to hear you got it fixed at a reasonable price. Happy motoring.