P0410 is the secondary air pump circuit. If the relay fails when open replace the relay block in the module box on the right side of the engine compartment. Always check the air pump motor operation by removing the rear plug from the relay block, jumper the heaviest wire to battery + and listen to what will sound like a vacuum cleaner. If the relay fails when closed the air pump will probably be burnt out. Jumper the pump feed to confirm as above. Relay block is around $125 and the air pump goes for $410. Another MB screw up, these relay blocks have been failing on every Crossfire we have sold and all at the 20K to 30K mile range. Another MB example of German engineering is the heated seat fiasco. Wire joints are at flex/pressure joints and the repair kit only gives you one chance to repair the seat covers. The next time the seat goes cold it's time for new seat covers $$$.