tdblewett

I have a 2009 R350 with 220,000 miles. Over the past couple months I started getting "key does not belong in vehicle" or it just doesn't start on the first try. Sometimes it takes a few attempts, but I haven't been stranded yet, which is probably going to happen any day now. Sometimes it clearly recognizes the key but doesn't start, and twice it has started and immediately shut off. I know it probably isn't related to the key battery because the ignition relies on induction. Anyway, I have two keys with new batteries that easily unlock from a distance and the same thing happens with both keys. I am lead to either the EIS module or the car battery. The current batteries in the car are replacements from 5 years ago. Any other ideas or ways to narrow it down?

chassis

@tdblewett I would get the vehicle to a known good condition or status. This means new batteries in the key fobs (they are cheap), new vehicle battery and new aux battery if the vehicle has one. 5 years is beyond what many consider the useful life of a battery.

tdblewett

Thanks for the advice, I will start there and see how it goes.