If it's as intuitive as the check engine lights we have today, it could mean anything from a slightly dirty plasma conduit to 'the warp core is mid-breach'.
You know, now that it's being discussed... with all the LCD screens in a modern car, it should show you the problem already instead of that bullshit light.
Geordi: It's nothing to worry about really, Data. If we were on the original NCC-1701, this would be a bigger deal, but on modern models like ours, we can probably safely ignore this for a while.
"... and for some reason the ODB 2 connector is under your console on the bridge, Data. You have to take the ashtray out to get to it." - Geordie, probably