Discussion in 'Engine & Drivetrain' started by dlnelsonroca, Feb 16, 2020.
That stinks. Have you reached out to GM for help?
tell them it's a ECM and or BCM Computer module issue they can fix it other wise they need to close shop..... that means they can't work on any other car as they all use the similar computer...
this is how to fix stupid
Step 1 pull suv into service bay
Step 2 get tech2
Step 3 plug in tech2
Step 4 turn on tech2
Step 5 turn on ACC
Step 6 enter diagnostic mode
Step 7 test Engine control module
Step 8 dealership pays you for training services.
print this out it might help him lol
Tell him to diagnostic as if it was a regular gas engine Tahoe..
the only difference between the hybrid tahoe and the gas tahoe is the HIGH VOLTAGE battery EVERYTHING else is the same. you got a much more POWERFUL starter 60kw starter, 185amp alternative-nator,Duo water pump, electric power steering rack etc....
the C126C says your Enhanced-BCM canbus is down
so lets go back to the basics.
wires are broken/damaged or disconnected, blown fuse??
check the BCM and ECM fuses first checking visually ( broken fuse might supply power but at a much lower voltage as the fuse will have a lot of resistance.. but will work "sorta" )
Check the fuses pull each one tell you find the broken one (with battery disconnected)
has battery been load tested? it might show good voltage but crumbles under load.. at start up requires about 300amp load..
with 100 computer modules on the canbus Aux pump (50amps) rad fans 20amps,hybrid fan 10amps lights 15amp etc.. it comes to about 300 amps with everything at once coming on when the key is turned...
a weak battery will crumble under this load... of course this is a peak load which will drop once the 12v Alt kicks in ..(just after start up)
Again, thanks for all your replies! IT's taken a while because we replaced a the oil pressure sensor, and found that the timing chain tensor was broken, and so replaced it and the timing chain. We also bought a new battery. Afterward the car ran great for about rwn minutes, and like before the codes started screaming in and the power was reduced until finally it shot off. Now it won't turn over or crank. So there's a new set of codes from my scanner, which was given to me by a mechanic friend when he upgraded a few years ago. They are P0C17, P0C18, P16F9, P0AC4, U1815, U1817, U1818, and U1820. We looked over the PCM and ground wires, but didn't see anything obvious. There's a Chevrolet dealership about 40 minutes away from us, but they've never seen a hybrid here. Any suggestions on what to do next?
Thanks, ChloeSib. So what did you do to fix the module communcation issues?
check the battery cables mine was pretty dirty under the rings
there was a TON of dirt causing electrical impedance
I did buy new cables (pain in the butt to find and very expensive ) but ended up cleaning the ones i got instead and it fixed my electrical gremlins.. I was getting random codes, at worst it stalled out.. yes i did get U codes... and crappy MPG as low as 12.5mpg
check on the terminals and pull off the bolt mine were pretty dirty under them(disconnect from the battery so you don't risk damaging the posts on the battery) it uses a 10mm socket.. that little bit of dirt and grease caused issues
see post #22, above
or call GM & have them tell you what dealer is trained to work on hybrids & work out something to get your ride there.
You all are lifesavers! So with a new battery, cleaning the cables, both the battery and especially the ground cable on the firewall, it fired up and is running like new again! Finally...
Thank you so much for getting back to us with the resolution to your issue. Much appreciated. We've added a confirming case to our knowledge base for electrical connection issues.
Often, it is the 'little' things that cause us the most grief to diagnose and resolve.
This also re-confirms why this Forum and its members are GREAT!!
Glad you found it! I've been in the same boat huge problems and the fix ended up being so simple makes you feel dumb.
Thank you for posting the fix might helps a lot of others!
Glad it was a simple fix sometimes it's the basic things that cause major issues hybrids are particularly sensitive to 12V battery issues.
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