12' Q7 Limp Mode

hey guys, got another crazy one here...

Last Friday I had it at home putting trailer hitch and all on it, in that time the battery got low from doors and what not being open and wouldn't crank. I hooked my cummins to it, fired it right up. But I did notice glow plug and TPMS lights flashing. So, I said well I'll run it around the neighborhood hood so wheel sensors will relearn. TPMS light went out but noticed it had no power and is in what feels like limp mode. Hooked scanner to it and has no codes. I tried re tuning with my Malone file again just to make sure it didn't do something weird when the voltage got low, but still in limp mode, no check engine light or anything. Tried driving it today after unplugging the DPF pressure sensor and i noticed glow plug light is blinking non stop now, so hooked my scanner to it and its got a P0237 low boost code in it that absolutely will not erase. Pulled sensor and cleaned just incase but it looked fine and not covered in anything. I cant see a sensor going bad out of no where just from battery voltage getting low. I also overnighted a VCDS system last night to see if it would delete the code. Its never done this, has been running flawlessly. Is there anything you can think of that would cause this from what happened with battery running low on me? Thanks in advance!

Define "trailer hitch and all". Normally, the trailer wiring involves the controller, which plugs into the harness, and the CAN Gateway needs to be told their is a new module on the network, and some other modules may require a recoding. Which would require a real scan tool (like VCDS). You'd also need a real scan tool (like VCDS) to go in and clear all the low voltage DTCs that have been set in all the modules, as well as check/clear/reset the battery regulation system so you don't fry the $1000 alternator. The Q7 is no Jetta. It is an exceedingly complex vehicle.

no controller or module, i tapped into some brake and turn signal wires on the hatch, but that shouldnt have anything to do with the engine being in limp mode. i guess we'll see what shows up in ecm when my VCDS stuff gets here today but as of now, im getting a P0299 underboost code and a 12896 which has no info and i cant find any info on that anywhere.

I am cringing right now, LOL.... "Just tapped into some wires".... yeah, well, the ECU may be getting a flaky signal from the brake input circuit right now, who knows. The wrath of the electrons is not good when people do stuff like this. I hope you get it sorted out. The CE module is not happy right now, that's for sure.

I'm not like most of these clowns on the internet, im very mechanically inclined, thanks. I also have my own diesel business. I didnt do anything that hasn't been done by plenty of other people on the exact same car and same spots.

Well then you don't need my help! Good luck!

No sir, wouldn't want you to "cringe" anymore than ya had to.

Bad move. Oilhammer is one of the smartest people on this site. Just saying. He has helped me several times with odd stuff.

lol this is great, GOTSMOK so you coulda installed the plug-n-play OEM Towing module that dynamically adapts the vehicles parking sensors, traction control, blind spot monitoring, shifting behavior, backup cameras, adaptive cruise, air suspension, hatch liftgate and more to the presence of the trailer, without splicing a damn thing.

But instead you went dumb and cheap, hacking into the electrical system of a vehicle you apparently dont understand nor respect, and then refuse to accept the fact you done ****ed it up when you have a bunch of electrical faults afterwords.. You say your not a clown on the internet, but you sure look and sound like one.. if your diesel shop does cheap half assed jobs like you do, we're all better off not visiting your circus.