It has to record ECM failures, it will note the speed sensor failure. Most of the questions can be answered here... Frequently Asked Questions (FAQs) - ELD Rule
Tons of drivers will be showing little chickenspit violations or have to stay parked more rather than go after those loads which might put them in danger of violation.
What angers me is that stupid 14 hour limit, combined with the increasing amount of shippers/receivers that some times take several hours to load or unload and will force drivers to leave the property whether or not their hours are up, dispatchers who are too incompetent to understand if a loading or unloading schedule will be screwed up by that clock, and then there's the parking issue, all of which the entire transportation industry and FMCSA has pretty much stuck their heads in the sand about, and little has improved after 12+ years of having that rule in effect.
It will have an error stating it did not get a signal from it, but you also have to contend with the other parameters being passed to it via the ECM. You also have to deal with latitude\longitude parameters, which shift at varying times so your exact location is not known, they are off a certain distance and it shifts. A good example is your house, once it is registered as your home, it will never show you there, it will have a varying factor of 10 miles.
Honestly my biggest beef with it is the short moves on customer property... likely going to result in many 15 hour "breaks"
Guy selling dummy speed sensors at the Pilot in Joliet, IL this morning. it has a dial and a digital readout - you turn the dial to set what speed you want it to report to the quallcomm. Said you could be doing 65MPH, as long as you have dial below 5 it can show you in yard mode.
Honestly when a shipper kicks you out of their property and you have hit your 14 hour rule, what steps do you take? Do you call DOT in that state and explain your situation and ask for a escort from them to a safe parking place?
This is the reason 100% automated self driving vehicles will not win. Human ingenuity will prevail This is awesome. A computer is only as smart as the inputs. Tinker the inputs, and it's just another dummy