Posting this here as Ash8's part thread is not seeing any help.

I'm in the unfortunate position of having to replace my ECU. Dealer if having problem finding a used one. I have an ECU Number N3H6 18 881M, I found the first replacement with this exact number (shipped out of California, I'm in Canada) failed on a final stage of the swap with a communication error. Not sure it it was a bad ECU or an incompatibility with a California units. Looking for another replacement but cant find another of that complete number. Here's the question will any ECU with the same initial 9 numbers work? I can find J,K, and L's just not another M. Does the last letter represent the Flash level ship or is each letter increment hardware change? Dealer also indicated N3Z2-18881L and N3ZD-18881B should work but they have not been able to find one of these either (they are unsure about the last digit question). Same problem 9 digits but not the final letter

Appreciate any incite.

One update: today the dealer supplied ECU (same part number as the original) same problem. Fails to communicate at the last stage.

 

I had issues when I reprogrammed a used one with the WDS not keeping a good connection on the OBD port

Check the pins on the connector

 

The connection was verified by the dealer using the WDS and the original ECU , communication... checked out OK.

The Issue requiring the swap is an immobilizer activation at low temperatures that was tracked back to the ECU, I could be remedied the problem by applying localized heat to the ECU? Not a very practical solution for a daily driver in winter.