M4 is a mode on your shifter. like PNRDM if you go down one from Drive what would be low range in a normal car is M in these trucks. you can drive in M4 and it won't go into auto stop mode. it will not go into the super overdrive on the highway so you get a little less mpg but it's good to know for the stalling.
since you have a scanner, read thru the thread linked and you'll get an idea what you're looking for as far as battery voltage goes and then log the battery voltage of all 20 cells. the state of charge (SOC) the over all battery voltage and the hybrid battery current then go drive. when you replay it, you want all 20 battery voltage to stay around 0.2v if each other cell by cell. since you won't see that unless it's a brand new oem battery, if it gets much worse than 0.5v-1v you'll notice it driving badly sometimes when it goes to start the engine while moving the truck at the same time, usually worse with the ac on. by 1.5v it will set a check engine light for a bad battery every now and then. by the time I changed my hybrid battery there were over 2v difference between cells, the pack was completely dead, got a code a few times randomly and sometimes it would feel like the tranny slipping in gear while backing up, the bucking sometimes, worse when hot out and max ac on. new hybrid Battery and the truck runs like new.
some good info in that battery tread. there's also an upgrade for the aux transmission fluid pump. if the battery isn't to bad, it might be worth trying that. it will cause the weird tranny issues too. I believe the upgrade is about 400$ with the new wiring harness and pump. they used the new pump from 2010 or 2011 and up trucks and made a retro harness to use it on the older ones.
the aux pump runs off the 12v battery and pulls a good amount of power, the 12v battery is charged by the inverter (no alternator) from the hybrid battery. so it's pretty important to have a good 12v battery to keep up with the current drain while the hybrid system is driving the truck and cranking the engine. especially if your hybrid Battery is getting weak.
if I put it in M4 mode, then the car drives fine. without any hiccups or problems. I have not checked the battery yet, no time
from the look of it, the code is thrown when the inverter can't output 42v correctly. it runs the steering and stuff. can be hybrid Battery weak, 12v battery is weak or the 42v system pulled more than 40 amps, either a short or some other reason.
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10-05-2022, 09:55 AM
Re: P1A88 help please
