Chat GPT answer had me make a change that caused “pre collision system unavailable”

[Jackdforme]

The long story short is this I have a 2025 flash. I’ve been trying to get the rain sensor working and while I wait for a harness, I’ve been trying to figure out if software is the reason that 12 V is not being supplied to the factory OEM three pin plug.

So I went to Reddit and someone suggested a ChatGPT answer which made a suggestion about asking the BCM to turn on the 12 V trigger for the rain sensor using 726-12-01. I changed the last digit of the first byte to a 1 from 0 and wrote that.

When I reset for that change, I got two errors precollision system not available and service advance track.
I performed the BCM reset and waited a little bit and restarted a few times same results.

I backed out the change to a zero and performed all of the same steps and yet I continue to get the same result and error.

Can any of you provide some wisdom here on how I can alleviate this could it be purely coincidence because I was in my driveway in a rainy environment in the dark when I started it?

I guess I’ll know tomorrow when I drive it, but if any of you have any insights, please let me know

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[Heliian]

These chatbots, like chatgpt are full of shit. Don't trust it.

 

[bmwhitetx]

I don’t know what you mean when you say you changed the last digit of the first byte. That location has 10 hex digits (4 bits each) and two check digits. Which one did you change? Position 2?

In looking at the spreadsheet, that location has nothing to do with rain sensor. Digits 1-4 together are the CDID name and digits 5-10 change the vin. You should restore the values and reset the BCM if possible.

 

[Jackdforme]

I changed digit four from 0 to 1.
After that ever happened, I reverted it almost immediately however, when I reset the ignition the error was still there. I reset the BCM module and that didn’t do it either.

I wonder if I need to reset IPMA or something else. As the last result before going to the dealership, what do you think about pulling the 12 V battery for 30 seconds?

 

[Tony Burgh]

Don’t truck in the ways of wizards. They are mysterious and dangerous.
Good advice in Middle Earth. Good advice today.

 

[Jackdforme]

Don’t truck in the ways of wizards. They are mysterious and dangerous.
Good advice in Middle Earth. Good advice today.

I’ve been so good until this moment. Every other change I made worked flawlessly. I have no idea why I listen to a dude on Reddit with a ChatGPT answer, but I deserve this in some way. I was really looking for something magical to happen like being the first person to find out that you could turn on the 12 V for the rain sensor in a 24 or a 25 and not need the harness. Alas, not only do I need the harness, but I may even need the dealership.

 

[bmwhitetx]

I changed digit four from 0 to 1.
After that ever happened, I reverted it almost immediately however, when I reset the ignition the error was still there. I reset the BCM module and that didn’t do it either.

I wonder if I need to reset IPMA or something else. As the last result before going to the dealership, what do you think about pulling the 12 V battery for 30 seconds?

Pulling the 12V for a few minutes will allow all modules to reboot which is definitely worth a try. I took a look at 7 other 2025 Flashes and they all have the following:
726-12-01 C100 xxxx xx--
726-13-01 C101 xxxx xx--
726-14-01 C102 xxxx xx--
These three locations (12,13,14) are where the VIN is stored in the module. Digits 1-4 are CDID and digits 5-10 (x) are VIN characters that are different for each truck. In fact all Lightnings across all years have those same CDID's. So CDID is the same and not vehicle specific. I do not know what CDID stands for. Google came up empty for me.

My theory it is related to VIN decoding/positioning. And for an instant by changing the C100 to C101, you made two different locations have the same CDID (C101), possibly causing a VIN mismatch across modules.

Good luck!

 

[K6CCC]

@Jackdforme If you look at the previous post from bmxwhitetx, look at his signature. At the very bottom is a link to a long thread with a huge amount of info on tweeking our trucks with FORScan. Far better source of information that ChatGPT.

 

[Jackdforme]

First, thank you so much for the detailed reply. It’s an accurate reply and what wound up happening is what I hoped would happen. The vehicle went to sleep overnight. I assume that made the IPA module go to sleep reset and then when they talk to each other this morning, everything was OK.

I’ll keep monitoring it but lesson learned for sure.
I guess I’ll just wait for that harness to come in

 

[Jackdforme]

@Jackdforme If you look at the previous post from bmxwhitetx, look at his signature. At the very bottom is a link to a long thread with a huge amount of info on tweeking our trucks with FORScan. Far better source of information that ChatGPT.

I used the thread v2 for all mods except my hunt to find a way to not add wiring and just buy a rain sensor. I have the rain sensor, the 3 programs in to get it working and get the DTC for the missing rain sensor which is normal. Wipers still work as normal. I will just need to wait for the overpriced harness for it now. I had this hope that there was something that would trigger the 12v connection to the sensor. I know I can pickup 12v from the mirror and run a 16awg wire down to the SCCM pin 3 and pickup LIN too but Im not cutting into the truck. Its my rule, if you can plug it in instead, do so. So I wait.

Thanks again, all. Great resources here.

 

[bmwhitetx]

... I have no idea why I listen to a dude on Reddit with a ChatGPT answer, but I deserve this in some way....

I've posted this before but it's one of my favorite sayings (no disrespect intended )

 

[Jackdforme]

I've posted this before but it's one of my favorite sayings (no disrespect intended )
View attachment 103161

ha, happy to help

 

[mr.Magoo]

I mean, "someone on Reddit suggested I ask Chat GPT"...

 

[chl]

To err is human to really screw up you need a computer...and the Internet.

I've posted this before but it's one of my favorite sayings (no disrespect intended )

 

[chl]

Why I don't mess with a truck that gets me from point A to point B and back again...

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