My truck is on larger tires, and my speedometer is calibrated with a Hypertech programmer. I'm about to replace the battery and have some questions.

When I worked as a mechanic in the late 90's, early 00's we would always replace batteries with the engine running so we wouldn't have to mess with radio presets. I was about to do the same, then I got curious about the Battery Management System, and whether that might trigger a check engine light. When I was reading up on that, people are saying that disconnecting the battery with the engine running could do some damage. This I don't understand. What could be damaged and how?

Fair enough. I'll replace it with the engine off. Now I'm wondering if I'll have to recalibrate the speedometer again if I disconnect the battery with the engine off. I'm also wondering if my transmission will have to re-learn shift points according to my driving habits like it did when it was new.

I know I'm over complicating a simple task, but I'm just wondering what to expect. Anyone who knows, your input is appreciated!

 

Never replace any Battery while the engine is running.
The charge system can command the Alternator to run wide open at over 15 volts without the Battery as a Load.
Your vehicle is a full computer system on wheels and is in danger of damaging Modules from the excess..
.
Your program change is safe. If you had to change it, it won't change back by itself.
Once you replace the Battery, reset the BCM to indicate a new Battery has been installed so its age can begin from new and charge control is commanded properly or it gets the old Battery control you do not want to have.
.
Also powering down the system will cause the PCM to re-boot and go into self diagnostics. This is a normal action and does not change the Program but does clear >learned< table data from drive cycles. It will learn that data all over again but not change any you made, from outside..
Good luck.

 

Thank you very much Bluegrass.

 

This is important.

While I can't say for sure if this will work on YOUR vehicle, I can tell you it has worked on a number of mine to reset the BMS:

1. Ignition ON, engine OFF
2. Note the solid BATTERY icon on the instrument panel
3. Flash the high beams (with the stalk) FIVE times
4. Press and release the brake pedal three times
5. Wait approximately 10 seconds. You should see the battery icon flash several times, then turn back solid.
6. Shut the ignition off.

If you see the icon flash, you have reset the BMS.

Another option is to just park the vehicle, lock it up, set the brake, and do not touch it - even with the remote - for at least 8 hours. Works great if you park at home and don't touch it until the next AM.

 

I saw that method online yesterday when I was looking into the BMS. It's a 2018 so that should work.
I'm planning on swapping the battery this evening so it'll be parked all night in case the reset doesn't work for me.
Thanks!

Update: That reset procedure worked for me. Thanks again.

 

I am happy that everything is well now.


 

nvm.