They've confirmed that the primary code creating this whole issue and the reason for the P0AC4 is P2797:Auxilary Transmission Fluid Pump Circuit Performance.
If anyone knows of any approach for this issue or Technical Service procedures that may exist, or even where I might be able to get parts please enlighten me...

 

Im thinking of getting a 2009 silverado hybrid but after reading this is the truck worth all the hassle?

 

blackheart, this is an odd case. 1) Issues like this should be addressed before delivery in US, and 2) as I said before this would be a straightforward warranty job for a US dealer.

I would think the S. American dealer would be glad to look one over prior to selling them for real, but that's just me. They should have online access to the service manuals for the 2-Mode hybrids just like they do for any other GM vehicle they sell.

The Aux pump system is two components, and you have two codes that point to one or the other. The P2797 means the pump bolted to the bottom front of the trans is not making the commanded pressure. The aux pump control module is mounted underneath the 12V battery. If it went south, e.g. wasn't commanding the pump properly, you'd see a P0C2B code. So I would bet on a bad pump.

 

What KC is saying is right....

Blackheart, I am the one who wasn't careful enough before shipping the truck overseas. I can't think of a better deal than buying either a Sierra, Silverado, Tahoe or Yukon hybrid. My Silverado handles the rough Andes almost too smooth. There is just bad service here. If I were in the US now, I would have no problems.

But KC please answer me just one question, could I buy the replacement pump independently? or even get the service manuals? and also, do all the models mentioned above share same exact aux pumps?

Thanks again for all your assistance, it is greatly appreciated

 

Not sure about buying one on your own. But the same aux pump is used for all Two-Mode transmissions.

 

The P0AC4 is always set just to let the tech know there is another code set. The P2797 and the hybrid cooling system codes are the ones to wory about. The cooling system on your truck is out under the hood not at the battery.

 

I was envisioning Sao Paulo or someplace on the plains of South America...Quito? The Hybrid Controller and ECM should handle this but hey...the elevation of Quito is 10,000 feet!!! That is almost twice as high as Denver, Colorado!(info for all you north americans) I can only imagine the confusion to an automobiles sensors. It is one thing to say it is controlled by the ECM but quite another to not expect that the temperature/humidity/pressure combinations in Quito could be vastly different from the logrythems that the ECM uses to make its calculations. Any of you knowledgeable tech guys have any inside poop into how the controllers compensate and would such a far end of the spectrum cause any problems that delasierradh should know about. Dang...I was glad to have some pavement to go to when flying in South America but Quito was always one of my last picks if I had a choice as an alternate, due to such high altitude and the complications it presents. The good news is that the battery and MG1/2 don't care...just the ICE!

 

Conditions in this city are pretty moderate, it's a constant spring so to speak, little humidity, not a degree over 75 or below 45 all-year-round.
But would altitude have such a high impact these cars' elements?
In this city there are tons of people driving hybrid Tahoes, Escalades, Highlanders, Lexus RX450, I even saw a couple MB S400s. None of these people have had issues as far as I know, other than Toyota's "Not designed for off-road" warnings.
Either way, I'm going back home to N Y to see if I can find the Aux Pump.

 

The controllers should..."should" compensate for the altitude but...10,000 feet is extreme and I would think any variables could contribute more at the limits of a controller than they would in the middle of the parameters. I would also think that this would be true of any vehicle, not just a hybrid. Before we had ECM's you had to tune a car for high altitude and when you drove from sea level to the mountains, the car would start running bad passing the foot hills. Not so today, but I am just saying that you are driving around like you are at the highest passes we cross over in the US and you are there constantly. So if it were an issue it would certainly be one there. But again, I don't think it is or would be, I am just saying your are in very thin air and extremes will be where issues arise more often. Yes, it is always so nice in Columbia and Equador but...you are a a very high elevation so that nice climate is also very thin. Your airport is one of the highest elevations in the world. Only LaPaz Bolivia is higher. It is so high, that even when the airlines take off and land there, the pilots are both on oxygen and breathing it during the takeoff and landing, even with the airplane being pressurized...because once they land or they are taxing for takeoff, they are above 10,000' and the airplane is not pressurized at that time. You are at very high altitude for the operation of any engine other than electric. Not saying they can't be tuned for it, just saying that if you have electronic controllers, then as they vary from the norm, they may have less tolerance for accuracy. I really don't know delasierradh, I am just speculating and when a tech throws the vehicle on the computer and looks at it, it is certainly different in the shop there than it would be here at sea level. I bet is is beautiful there though surrounded by the northern Andes.

 

I've been up on Mt. Evans a bunch of times. 14,000 ft. No big deal. The engine has a baro sensor and MAP. It's "tuned" already it should be fine. That pump is most likely the the major problem.