From what I've read, my friend needs to check his lambda duty cycle and possibly the LED if his car is from CA. I crawled around and can't find any table of fault codes & duty cycles (on-off ratios). Can someone point me in the right direction? What years of KE gave fault codes in this fashion?

Thanks,

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Dave

2002 Audi S6 Avant
1983 300D
1984 300D (sold)
1990 560SEL (sold)