The only diagnostics on your car is the off-on ratio read out that you are looking at. To read it properly you should put your scope in the duty-cycle function and read the duty-cycle. A proper working car will have the off-on ratio (duty-cycle) varying back and forth in feedback (lambda) control. A proper working AND adjusted car will have it swinging about 50%.

If you have a fixed duty-cycle at even multiples of 10 (10, 20 ,30 ,40 etc.) then you have a current fault displayed. Fault memory is not maintained and if a fault goes away so does its indication.

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