Code scanner only connects with engine running
I have tried three different scanners on my 2012 GL350 and none of them will connect unless the car is running. I turn key fob to the pre-start position, plug in scanner, it goes through all the protocols trying to connect and returns "communication failure". I have two Autel scanners newest is the MD808 Pro, and borrowed one at Autozone (think it was Innova) with same results.
Once I start the car it connects quickly. No issues with the car at all, I was checking for codes prior to state inspection to avoid any surprises.
I scanned it 2 years ago and it had no issues connecting in the pre-start condition. Is this something related to the keyless-go?
Any suggestions appreciated



