I seem to remember reading some where that it keeps a fault history saved of why cruise fails, I believe he might be right about braking is very complicated in these trucks. one of the calibration tests I've seen seems to adjust the brake pressure to the wheels vs peddle movement so regen works right. something about it recording how far the peddle moves to make 500psi of brake pressure. I didn't run the cal but will if I ever do brakes and rotors. never seen that before on any car. kinda wild, but also I gotta remember these trucks are basically 2005-2007 technology levels while in development. by now hybrid stuff has come a long way in development by 2022. so what seems weird now was all they could come up with back then.
just looking for fault codes for the battery and checking the voltages at rest with a scanner is a pretty incomplete way to test the hybrid battery. you really need to see off the cell voltage while it's trying to crank the engine. which is pretty easy with the right equipment but not something most think to do, because of how oddball these trucks are. I don't believe that's a common issue with a prius type hybrid they probably have more experience with.
I've got a log of mine on the old battery, where you log battery voltages and the amp being pulled from it. so like let the truck go into auto stop, hit log. turn the ac and stuff on and just watch the voltage, all should stay within say half a volt for a decent battery, 1.5 before you see check engine light. mine was more like 2 volts, so I knew it was done. but then when the engine started it caught for a split second 75amps draw, lowest cell high 9v highest cell held 14v. 16ish is normal. so instantly you know the hybrid badly is dead but also less than 3 sec so no check engine light and that's just parked, now if it's trying to move the truck which I've seen pull 50 amps doing and add cranking. the whole system can't keep up. which leads to that aux tranny pump, it doesn't exactly run off hybrid, it runs off the 12v, but the 12v system is held up around 14v by the inverter running off the hybrid battery. well the hybrid system just tanked for a sec while cranking so that aux pump is running fully on the 12v and it's probably going to drop to 10v or so under that load. I'll attach the screen cap of the log, you can see with a 2amp load which is normal auto stop without the ac on to ac on and engine cranking. the min hybrid cell voltage to the max cell voltage difference is just crazy high. but it doesn't show up unless you're specifically looking for it
so yeah, the whole system is tied together, during the production run they made a change to the 12v used, to one with a higher reserve rating. Lotta 12v load in these trucks, the aux tranny pump has a 60amp fuse on it, gm usual fuses pretty high, so while I haven't found a place to stick an amp clamp on it and command it to 100% duty cycle, my guess would be 30amp draw with a 45amp spike if needed. still enough to pull a charged 12v down into the 10v's. I feel like if it gets bad enough the line pressure in the tranny can't keep the clutches from slipping while it's lurching and bucking, not only is it annoying, you're causing extra wear on a clutch packs in a tranny that's going to be difficult to find a repair shop to touch. I'd rather avoid all that and not just get used to the bucking and stuff.
with the cooler weather coming, you might find it running better. mine definitely did. the difference between running max front and rear ac on 100deg day vs a cool morning with the windows down was night and day.
long windy post to just say you should probably not listen to the mechanics battery test and pick up a 20$ scanner and the app, and keep an eye on how your battery is aging yourself. you'll most likely do much better than them and save any surprises. I swear mine went from yeah, I'm buying this truck knowing it will need a battery but being surprised how good it was still working to 6 months later getting lurching and bucking and bad signs the battery was toast.
you did remind me I need to check the engine mounts. I had to replace the ones in my c6 about 100k, wouldn't surprise me if these are bad too haha. ugh. all that jerking and lurching is probably ******* them too.
