After the installation of MY gmtu
I am back to the old hard brake pedal in the morning once agai.
My dealer said it was the correct reflash they even showed me the paperwork
Tom at Crate Engine Depot said he never heard of there being a seperate
flash but it clearly states there is right in the instructions.
My dealer has been great about this but they said they want me to drop the car of so it can sit over night then test it .
I am pretty sure that this pump is supposed to run
either
all of the time
or at least the first say minute or so?
I am just trying to figure out if anyone knows or could check when theres is running.
Another words if it runs every start and mine is not running then either a wire got moved during the install or something is wrong with the reflash?

 

I believe it runs as soon as the key is on. You can hear it at the front of the vehicle. It is by the oil pan down low.

 

Thanks chevymgr.
That's what I thought and I should have checked that on my car when the brakes where working properly after the install.
can anyone out there confirm this for me.
That way my Chevy dealer would not need to keep my car a couple odd days.
if it is supposed to work as soon as it is keyed.
Mine was installed with a nice bracket that bolts right to the front of the oil pan.

 

I can't 100% confirm. All I know is it makes up for the lack of vaccum in the system upon cold start up. The lack of vaccum only lasts about 30 seconds-1.5 minutes while @idle. I would assume the pump would only run at that time. Like I said not 100% on that one.

 

Still wondering and doubting that my GMTU reflash had anything to do with it but it seems that it is possible why my pump is not working

 

I know for a fact that there is a seperate flash. I had my car reflashed once, and they flashed it with the brake assist flash (even though I do not have it installed on mine). When I started it up, it threw a brake booster code. I told the dealer about it....and they thought it had the brake assist. I told them that it didn't. So, they reflashed it with the correct flash and it cured my CEL.

 

Hey Mike,

The vac assist can bleed down overnight. you have brakes just no pedal. These cars have drive-by-wire for gas, steering, brakes. Its the pedal that isn't there. Best way to insure you have them is either wait for the idle to settle down or your boost guage reads in the -18-20 range, usually around the same time. Its almost as if the motor is idiling slightly higher to build vac quickly, then it settles down.

I liken the the way the vac system on this car is to that of an air compressor charging its tank, the car has to build up vac in the same way a compressor fills itself to specified pressure

 

Thanks for the info.
I use to wait then the brakes would be fine.
Then I had the electric vacuum pump assist hooked up and it eliminated the waiting.
You could literally start the car up roll down your driveway and brakes where great all the time.
Now after the gmtu it's like the vacuum pump was never added.

 

Correct....
Start the car, & go...
With electric vacuum pump assist, Zero waiting time...

Ya, they flashed you with the wrong file, or disconnected the pump, when putting the lower sensor in.
Are they 'fixing' the bog too...

 

It appears to be the correct flash
I wish I could get an actual gm flash code # from someone else with an 09 automatic with electric vacuum add on and a gm turbo upgrade that way i could confirm that they are using the correct flash for the ecm.
If that can be confirmed then its sounds like a wiring issue with the vaccum pump.

The dealer did grind the sensor and now it sits flush
It seems to run better. and has not popped up like it did before under boost.
I have not had a chance to take off quickly from a light to see if it bogs.
Hope to try that soon.
definently moves along pretty good with the GMTU
amazing how the boost is right there when you need it.
and spinning the tires at like 20 mph is something I never thought I would see out of this car and these tires.