2015 Rogue SL 2WD: ABS, traction control, brake lights on. Also chassis control error & key malfunctions. Also speedometer didn't work. Turned car off and everything is back to normal. Lights came back on and brought to ASE mechanic and he scanned and said it looked like the ABS module was not communicating with the computer and that this is a dealer repair. Turned car off and then back on and all lights are off and everything back to normal. Dealer said bring it back when the lights come back on, no codes when everything is normal. QUESTION: Could a speed sensor be doing this? If so, any particular one that controls the speedometer along with ABS, Traction control, etc.? Other thoughts?
Thanks in advance.

It could be the ABS, but it could also be a bad cluster or a CANbus problem. Getting the diagnosis right will depend very much on getting all the codes from all the systems, past and present. So I highly recommend you pay the dealer to read the codes and print you out a copy of the Consult3+ code sheet, and also print out "Freeze Frame" data for any codes where it's available (not all codes produce a stored FF). The speedometer going out complicates this, because the cluster gets speed info from both the tranny (VSS) and the ABS wheel sensors, and it will generally function with either one. Then the cluster forwards the speed reading to the ECM, which will complain in turn if it doesn't get it. The bottom line is, without finding out who isn't talking to who and what errors are being flagged, it's impossible to even know where to look.

Thank you very much. I hoped it might be simple, but...
Thanks again, I'll do what you suggest!

You're most welcome. If it doesn't look like anything obvious, post the codes and FF's and I'll analyze them for you.