Yes. If the engine is on, the sensors in the seats are functional and the engine and systems status will be recorded for about 20 seconds before a crash and about 5 seconds after a crash (even in water). There’s a federal regulation (part 563) that governs these EDRs and dictates that they must work in the event there is a change in velocity of 5 MPH or greater
I think this means they would be suspicious if the EDR were on and recording and there were no change in velocity (meaning slow roll into the water), or if it weren’t recording at all (engine not on).
Earlier on in T1/T2/T3 there has been a lot of discussion about EDR data—LE will have this data And have already formed opinions based on what it points to. This and COD/toxicology will be the most revealing first major pieces of information.
Here’s another document about EDR reports:
https://static.nhtsa.gov/odi/inv/2014/INOT-DP14003-61944.pdf