I'm trying to figure out
a) possible causes of the ESP light coming on
b) Whether it's possible to retrieve more info from the system as to exact error
c) the likelihood that the error relates to the work done
d) whether the part can be replaced myself (it looks physically/electrically simple, but not clear if any calibration/diagnostics programming is required)

I too am concerned about the wheel speed sensors. I'm interested in whether a fault in one of those (which is physically close to the working area) might cause this issue.

Initially I thought yes, but then noticed there's no ABS warning lights -- wouldn't that system have issues if a wheel sensor wasn't working