2003 Mercedes W163 ML55

Battery was dying and I made several low battery starts, had to charge for an hour or jump to get the truck going.

Changed the battery to a new battery and used the remote to open the door without issue.

Tried to start car and it starts then instantly dies and the odometer displays "Start Error".

I checked the battery again, poked around, locked and unlocked the car with the remote with no issue and the same issue happened when trying to start.

I tried to resync the key as follows:

Doors closed > Key in ignition to pos 2 > Remove key and quickly hold down the lock button while pressing the unlock button 5 times > release all buttons and press the rear hatch button on the fob once. Put the key in the ignition and start.

This time the alarm went off. Removing the key I find that the remote will no longer lock or unlock the doors at all. Repeated the sync again - same result.

Scanned the DAS module with icarsoft > Code reads "Transponder can not be read"

SO there I am, the transponder can not be read and it does not like the radio remote either. Now what?

Remove the DAS and see if it is wet or has poor connections?

I have only one key and Mercedes says they can not get a replacement as they are on backorder.

Ideas?

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