Hello everybody, new member here, a little bit about me and my issue, I've been doing mechanical work for about 40 years, as well as I'm an Electronics Technician, so I have a pretty good knowledge of vehicle mechanics and electronics, I picked up an 09 Chevy Tahoe Hybrid a few months ago, thought it would be a decent vehicle since the previous owner just put in a new Jasper motor and new lifetime warranty Hybrid battery, it's been pretty decent until I got a couple of codes indicating the infamous auxiliary transmission pump controller issue, I checked and cleaned the contacts and it would go away for a while, but then come back on as well as the jerk and bump issue. I secured a new replacement transmission controller, and after retrofitting the connectors installed it three weeks ago and everything has been great, no more codes, engine and transmission and stop-start function all work fantastic. Because of my job, I'm sometimes out of town so the vehicle has been sitting for about a week and a half or so, I went to start it today and the check engine light came on immediately and when I pulled the codes, I got the failure to communicate with the transmission module code, sorry I can't remember the exact ones because I only have my cheap scanner here, as well as a few other miscellaneous auxiliary transmission pump codes. I disconnected the battery, as I wanted to take it for a test drive after I replaced a front hub which was bad, and then when I took it for a ride, I got check hybrid system warning graphic, I saw a quick parking brake graphic but that one away right away, and finally my trip ended up with reduced engine power graphic and could not barely drive home much more above 40 or 50 miles per hour with a High Rev. It's in my garage right now because it's late and haven't had time to look it over very much except I removed the engine cover to make sure no rodents have got into the engine like they did in my van and chewed up the wires which I did not see any evidence of, so, anybody know where to start once again? Could the actual transmission pump be defective and should I replace that? I do have access to a much better Snap-On scanner at my buddy's shop that I can probably bring home tomorrow, but that one usually shows the same artifact as the one I have. One interesting issue I'm having with the vehicle is and it seems silly to say, but when I park the vehicle and turn off the ignition and get out, I hear all kinds of strange creaking sounds coming from the driver side wheel well area behind the tire, almost as if the brake pads are trying to energize themselves oh, and I also hear a bunch of thumping under the hood, not quite as if the ABS is activating but something weird like that, any way anybody have any ideas for this possessed vehicle please let me know because at this point in time I'm probably looking to trade it in or sell it and don't want to do either until I can at least get it fixed properly, I appreciate you reading my long dissertation and look forward to any help!
**As an update, all of these issues seem to have been caused by a diminished 12-volt battery, surprisingly I gave it a good charge because the vehicle has been sitting for numerous days, I reset all codes with my scan tool oh, and have been driving the vehicle for several days with no issues going forward, guess I have to make sure I either Drive the vehicle more often or keep a charger on the battery.

 

Check the battery terminals clean them good with electrical connection cleaner.. use a stiff nylon brush not a metal one.. scratches = poor connection
I cleaned all of them even the MEGA fuse connections

you should be getting 14.48-14.5-VDC volts reading steady output from the inverter I turned on all the electrical stuff HI+low A/C, heated seats and rear a/c etc rolling windows up or down.... at 4 at the same time
I took it out for a drive to day and it ran perfect... Good mpg as well... it's also shifting at the correct speeds with the AFM disable chip before it was not shifting correctly with the chip



it was shifting at 48mph instead of the early 40mph....

before i was getting 13.1-13.3v my battery was never charging correctly it was at 12.1v volts

12.1 volts is observed at the terminals the battery is 10-20% charged.

I have a Deep Cycle battery (AGM) so no worries..


had it charged up at autozone(it was free) then cleaned them up REALLY well 10mm bolt btw (10mm deep socket and extension for the mega fuse location )... looks like it fixed the transmission stumbling as well....... i meet the criteria where this stumble or Shudder, happens but it did not happen typically at 10mph after a cold start

besure to disconnect the battery before any cleaning it as electrical cleaner is flammable sparks may ignite the fumes this also reduces the risk of a short circuit...

 

Common issue the Hybrid systems rely upon 12V power and if it is low the gremlins appear and wreak havoc.