If your code appeared after replacing the air filter be sure the tube from the AMM is tight to the throttle housing. I have seen the flexible section come loose on the hard section of the tube. This was particularly on a 430 but the concept is to have a sealed housing from the AMM on into the motor.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician