I took in my 2013 Fiat 500 Pop for new spark plugs and rear brakes. My next errand after the repair was the post office -- after a 30 minute wait, I came out to see my headlights were still on. Immediately after the tune up! My dealer insists the two cannot be related, and is insisting I need and must pay for an entire new body control module. I cannot accept that this is a coincidence. Any explanations? Thank you!
I honestly can't think of a feasible scenario where changing out spark plugs would cause issues with the BCM (TIPM). I suppose disconnecting / Reconnecting the coils while the battery is still connected could (theoretically) result in a loopback surge to the power box, but we're talking lottery winning odds here.
It's more likely you're experiencing a genuine BCM/TIPM issue. They are prone to issues, especially in the cold winter climates. I hesitate to use the term "failure" because there's a big difference between a complete circuit board failure and a simple corroded wire coming from the box. I would have a trusted mechanic run some computer diagnostics on it before shelling out $700+ for a new part. No way to diagnose it over the internet.
NOTE: I'm honestly not saying this to rude, but you do have one of the most unreliable production vehicles on the planet, so I recommend doing your homework.
You might not be wrong! Check your plug connections though!
Make sure the plugs you used are of the proper OEM material.
Because, just as an example, if you used nickle plugs, on a 2004 Ford Escape, instead of irridums, your security light will flash, and your vehicle randomly cuts off due to the improper spark plugs causing Radio interferce in the wires.
Radio frequency is a thing in cars, just like it is in computers.
Now if you disconnected the battery, to change plugs, reconnected it and randomly found body codes (U1000's) that could also be normal as the computer is just reporting that the battery was disconnected at some point.
As a technician, I'd clear them out, see if they return, and keep note if anything in the vehicle actually isn't working.