Gentlemen, I recently buy a 2008 Hybrid yukon and the was in very good shape. I forgot key in the ignition and the battery dropped. After a complet charge, I restart the truck and I had problem with stabilitrak. I did some
check and I disconnect the battery. Now I have problem with stabilitrak, abs, brake soon and pedal is very hard. I saw in this post that is possible to make a new programmation to fix it. I would to know what is this beacause dealer in Canada doesn’t know what is my problem.

 

When you fully discharge a 12V battery, it is permanently damaged. Before pursuing any other solution, have your 12V battery LOAD TESTED at an auto parts store.

 

Can the dealer talk to the brake controller? Get part number and programming state from it?


Simple scan tool task NOT hybrid related.

 

2009 Tahoe Hybrid 220k miles. Bought 18 mths ago and have driven it over 25k miles with zero brake issues. Today I have lost brake power boost and have a OBD Code C12D8.
This seems to indicate "ABS Base Brake Open Solenoid Driver Shorted" I am not sure what and where this solenoid is that is apparently shorted per that OBD Code C12D8?
On the dash the DIC cycles through service stabiltrac / service traction control / service brakes soon messages. I have the following dash icons lit up, "Red" Brakes icon / "Yellow" ABS icon / "Yellow" Traction control icon.
Brake pedal is no lower than usual it is just really hard to push, like takes both feet. it is not safe to drive out on the road without the brake vacuum assist, the stopping distance is greatly increased!
I suspect that there is an electric vacuum pump somewhere in the system? Does anyone have a link for a schematic/layout of the GM Hybrid braking system parts and controls?

 

There is no vacuum assist. There is a smaller than softball sized black hydraulic accumulator under the vehicle on driver's side with most of the electric brake components. Lots of brake lines to it.

From the really hard pedal effort it sounds like you are in Manual Push Through or "Foot strong" braking. Yes you need to get that electric brake pump and solenoids checked out.

I don't have a schematic but on-line service should be somewhat helpful. The master cylinder under hood is the manual part you feel now. The rest of it is under the vehicle in pretty much one device with that ball shaped accumulator. The electric pump, solenoids, and multiple pressure sensors are all in that under-body unit. You may wind up replacing all of that

Good luck!

 

OK well I have found some very interesting information that might help some GM hybrid and possibly just regular ole GM Truck vehicles with Brake issues.

First OFF Hillbilly is 100% correct this is not a vacuum assist system it is a GM Electro-Hydraulic system. There is a supply and return line from the master cylinder reservoir down to the ABS assembly under the truck tucked up beside the frame rail under the drivers seat area. This ABS assembly includes a high pressure pump/accumulator/valve body and a control module. This assy controls all brake boost/Stabiltrac and ABS. There is a control module with solenoids mounted onto this assy that is easily removable and that is what was bad on mine. It had a seal leak at the top and had gotten water inside which over a period of time ruined the solenoids. It had been leaking long enough that the chrome coating on the solenoids had rusted off in some areas!

Apparently GM's ABS Assembly supplier for these particular parts was not real good at making a 100% gasket seal on their parts. Every time you drive in the rain the part is exposed to moisture this is a BIG TIME mess up on the part of the the supplier! Not sure but I think it is a TRW Kelsey-Haynes supplied part?

When I got the old ABS Control module off it had obvious water damage on the solenoid assemblies on the inside. The seal at the top had been leaking for a very long time and destroyed (shorted) the solenoids. I guess the DTC codes are pretty darn accurate LOL.

Apparently this is a common design throughout the GM truck/utility vehicles in the 2008 / 2009 and maybe up to around 2013. The Chances of mine being the only ABS control module with a gasket seal leaking like this is highly unlikely. Probably thousands out on the road with the exact same issue, they will have a brake issue soon if they have not already!

Anyway I found a used 2009 Tahoe Hybrid ABS assembly (entire assembly) at a local junkyard. Bought it today for $256.00 tax included and swapped the ABS control module off it to my valve body. Took less than a hour. Note: I had ordered a new ABS control module from rock auto at $199.00 but canceled that order this morning because I was afraid that I would have to go to the dealer to get it flashed to match the vehicle.

That dealer flash process would have added a lot of time and cost (probably $100.00 min to flash at dealer?) Just be careful to double check your RPO code if a Hybrid it will most likely be a J92 RPO Code for 7,700 lb active brakes. It seems to be very happy coming from a nearly identical Hybrid into mine so no dealer reflash required.

I have driven around for about an hour and all DTC codes and dash lights are out and it drives normally. So far so good, knock on wood.

Got some pics here...........if you want more pics let me know and I will send them to you. I am going to keep the junkyard assembly for a while until I make sure everything is 100%.

Junkyard part tag interesting that is has the donor VIN on tag

Valve body on my Tahoe had to clean the top seal surface

Small hands can reach the bolts easily

Water Contaminated Old Part pulled off today 2-17-2020

Junkyard assy off a 2009 Tahoe Hybrid J92 RPO code part

Another view of the junkyard assy

Part numbers for the water contaminated pc that came off my 2009 Tahoe Hybrid

 

I'm having a similar issue with my 08 tahoe hybrid. I bought it from a used car lot and 2 week later the hybrid battery died on me so I got the battery replaced but now abs, brake and stabilitrac lights are on and I have no power braking the 2 weeks I had it previously there were absolutely no issues with the braking. Does anyone know the cause of this or how to fix it?

 

code was c12ff

 

I wish that I could report that just replacing the solenoid module was a long term fix BUT it was NOT. It worked for a few months then was out again with multiple codes and no brake boost.
I bit the bullet and took it to the dealerships and SURPISE they could not even order parts (parts obsolete) so that was a dead end.
I ordered a used part the entire assembly AGAIN since I threw the other one away LOL and had a local garage flush the brake system and install the entire assembly and it has been working great for about 6 months.
They had a very hard time getting it to program, but they were able to do it and saved me a trip back to the dealership.
From my research the issue is that basically No One ever changes out their brake fluid. These Kelsey Haynes brake units contain multiple bored cylinders and plungers with tiny orfices and the old/dirty/water contaminated brake fluid if left in long term scores the cylinders and causes the internals to lock up. Apparently we need to be changing out brake fluid like we do engine oil Hahahaha

 

I change or flush brake fluid at most pad changes, because the old way of compressing the piston back to put the new pads in pushes fluid, crap, and dirt into the abs system. Best to open bleeder to relieve pressure and push piston back, then flush so fresh fluid thru after all done as well. Although front pads on my hybrids went 140k before needing changed.