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.
This is not a vacuum assist system like in the old days, it is a GM Electro-Hydraulic ABS 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
This is not a vacuum assist system like in the old days, it is a GM Electro-Hydraulic ABS 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