The ECU monitors the oxygen sensor response to determine the operation of the SAP and sets a code and the CEL if it fails. I think that's why most people replace them when they fail.
Originally Posted by FLE39
Lean is not an issue for cats. They are a catylist. They only react to what is introduced. Rich, that will deff overheat and clog them.
As for the SAP. I'm glad I educated myself and found it and all. I am worried baout the check valve though. I may take it apart and see about cleaning it. Or price a new one. The SAP blows air into the exhaust system so the unburned carbons have a Oxygen supply and a chance to further burn off. Only works when the car is cold as about 10 minutes later when your Cat is up to temp the SAP is not required.
2001 530i/5 S+P CDV delete/Akebono ceramic pads
M5 SSK/RedLine MTL/M5 rear sway bar/Bilstein HD
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