Battery Management System Reset

[Cobra Jet]

So what was the purpose of these sensors if by purposefully disconnecting them there’s really no negative affects to the vehicle’s electrical or charging system?

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[Zinc03svt]

So what was the purpose of these sensors if by purposefully disconnecting them there’s really no negative affects to the vehicle’s electrical or charging system?

My take (may be totally wrong) is this management system is to make a battery last as long as possible. Problem is the car needs a healthy battery in order perform correctly throughout the entire electrical system. I think it shuts down and lowers voltages in order to technically try and save itself. Long run great for battery, but not good for chasing weird issues with car. ??

 

[Smokey613]

I also read somewhere it may be used to reduce constant alternator engine load to help increase fuel mileage. This would not surprise me at all.

 

[Smokey613]

I drove mine about 80 miles today and the voltage fluctuated between 13.3 and 14.1 I know it sounds strange, but the Mustang seemed to idle more consistent/smoother and it was 98 here today. I only unplugged the negative cable sensor.

 

[DetroitMustang]

Dealer called today, said Ford told them to replace the battery current sensor.. DUH, that's what the DTC said. Oh well, they had to order it, so I'm awaiting another call.

 

[DetroitMustang]

So the part came in, they replaced the POSITIVE side sensor. Seems to be OK, but I'll know more tomorrow after it sits for 8 hrs and resets.

 

[thehunterooo]

So what was the purpose of these sensors if by purposefully disconnecting them there’s really no negative affects to the vehicle’s electrical or charging system?

Basically it tells the car how the alternator should charge the battery. Which is why you always see voltage jumping about, but if you discount them it will charge like an old car. In reality it is supposed to increase battery life but my oem battery died in less than three years with the smart charging engaged. Disconnect it will have a dtc but unless you run the codes on it you would never know. I ran mine for over a year without issue ofc. The BMS system is still intact and if the battery is actually going out the car will go into low power mode. It just won't adjust the charge rate.

My OG problem was is my system would not reset on its own even when the car was almost stock so its not like a tune was messing with the BCM/PCM, etc. If the car sits for 24 hours I think it should reset on its own but mine never did. Even with a new battery the car thought the battery was bad and would not charge it correctly. This caused an issue as low power mode would let you run power acc without the car running. I needed to add my E85 tune and can't tune when the car is running, tuning and the car power shutting off can brick the computer. Lund never even knew of the system when I was trying to figure it out originally. The BMS can be forced reset via dealer/computer but I said screw it and didn't want to play that game anymore. I wouldn't really worry about it unless the system wont reset on its own or the sensor(s) go bad. I wouldn't spend the money to fix it.

 

[Smokey613]

I drove mine about 80 miles today and the voltage fluctuated between 13.3 and 14.1 I know it sounds strange, but the Mustang seemed to idle more consistent/smoother and it was 98 here today. I only unplugged the negative cable sensor.

What I failed to mention was before I disconnected the negative sensor my voltage fluctuated between 12.4V and as high as 14.3V. I noticed that when idling and the voltage was in low 12 V range my car would “stumble” occasionally. Since unplugging that sensor it never drops below 13.3V and it no longer stumbles sometime while idling. Coincidence?

 

[DetroitMustang]

What I failed to mention was before I disconnected the negative sensor my voltage fluctuated between 12.4V and as high as 14.3V. I noticed that when idling and the voltage was in low 12 V range my car would “stumble” occasionally. Since unplugging that sensor it never drops below 13.3V and it no longer stumbles sometime while idling. Coincidence?

Not a coincidence, Mine is running so good now, I had hesitations and bad shifts too. I just hope it stays the same tomorrow after sitting all night and resets.
I have the digital dash and mine only shows like 13.5 or 14.. I don't get numbers like 13.4 or 12.3 just half numbers.
Since they changed the sensor I've only seen 13.5 and 14.

 

[Smokey613]

Not a coincidence, Mine is running so good now, I had hesitations and bad shifts too. I just hope it stays the same tomorrow after sitting all night and resets.
I have the digital dash and mine only shows like 13.5 or 14.. I don't get numbers like 13.4 or 12.3 just half numbers.
Since they changed the sensor I've only seen 13.5 and 14.

I have seen voltages at every .1 from 13.3 - 14.1 since unplugging mine. The best thing is it never goes below 13.3V anymore.

 

[Zinc03svt]

I have not seem mine drop below 14.1 since unplugging both.

 

[Diocletian]

I have not seem mine drop below 14.1 since unplugging both.

Im thinking about doing this. I've seen it get as low as 13.0v on the digital readout. Just for peace of mind lol

 

[H1shawn1]

Just pulled the sensors and seeing constant voltage at 13.7 for my two short trips since. Plan on using forscan to try disabling BMS as well. Kinda curious if it'll make a difference. My thought is it's possible that even with the sensors unplugged to computer may be stepping in just a bit, perhaps due to intake temps????

PS I'm doing this because I just upgraded to a heavy duty lithium car audio battery. Resting voltage had been disappointing with BMS active but trying to take full advantage of the new battery.

 

[Zinc03svt]

Still running great unplugged. ;).

 

[frank s]

I thought I would take a picture for future reference if anyone was interested. Thanks go to those that pointed me in the right direction. These are the two sensors that thehunteroo was talking about. My system seems to be working fine and it has a new battery with a January 2019 date so hopefully I will not have any issues. But it is nice to know for future reference.

Just curious and looking at the location of the sensor plugs in my 2018 automatic's engine compartment, I was dismayed that the positive connector wasn't visible like Smokey's. I found it under a monstrous piece of equipment. What the heck is that? Seems as if someone drew a line on it with a silver Sharpie™. Negative cable sensor looks normal.

Not that I'd ever consider disconnecting something Ford clearly invested a great deal of engineering in, just to get my possibly innocuous gauge readings in a line.

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