JEB
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- Joined
- Aug 15, 2021
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- Location
- Northern Illinois
- Vehicles
- 2021 F-150 Lariat Powerboost
I can’t answer all of this theoretically. I can say that empirically, the first time I tried to reset a module I erroneously disconnected the negative pole on the starting battery and power to the modules remained. I also read the shop manual, which said that to cut 12V power, you must disconnect both the starting battery and the auxiliary battery. It further stated that, to replace the starting battery, you must also disconnect the auxiliary battery or “damage may occur.” It wasn’t any more specific than that. I presumed they were talking about draining and damaging the auxiliary battery, which is only 7.5Ah, which isn’t much.Isn't the PowerBoost auxiliary 7.5Ah battery on a PCM controlled relay which is normally open while the vehicle is off, cold cranking, in generator mode or in auxiliary mode? I had the impression the auxiliary battery circuit only closes to connect to the 12V bus when the PowerBoost is in its drivable 'Ready' state and lots of accessories are all drawing a load at the same time.
What I'm getting at is disconnecting the engine compartment battery in a PowerBoost while it is off should shut down all the ECU's the same as any other F150... or so I thought.
As an FYI though we can manually force modules to reboot through ForScan which achieves the same thing. I think the GWM has a general handshake bug or routing table cache issue of some sort because on more than a few occasions I've encountered modules that need to be rebooted to establish full functionality again after making any changes to their as built parameters.
Does FRDS offer a similar forced ECU reboot diagnostic function? it may save some time for people depending on the circumstance.
P. 49 of the F-150 Hybrid Modifier’s Guide also provides what I think is a consistent description of the operation/role of the auxiliary battery. It can be found here: https://www.fordservicecontent.com/...t/2021-2022-F-150-Modifier-Guide-MCS-6052.pdf
I’m not sure how much of this question I’ve answered, but I’m pretty confident about the effects of disconnecting the 12V battery only.
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