Hi all,

The end to my engine light and PCM coding error was all too predictable: An RCM with dry solders.

An auto electrician using a mercedes code reader detected live errors in O2 and Supercharger ground, but traced them back to the RCM. Resolder the joints and everything cleared.

The PCM coding error was a stored error, not live, and not relevant to this problem.

Thanks you all for your comments, and to those who insisted I check the RCM!!!

Although the joints are probably now good, the relays might not - so I plan to buy a backup RCM to carry in the car.