I have to smog my diesels too and they have always tested between 0 and 5%. My 87 300D tested at 0%! Ironically I was belching out huge clouds of black smoke under full throttle shortly before the test to "prepare" the car. And I have to pay $36 for this silly test.

Brian, if a diesel car was tested under gasser rules it might fail on NOx but it's very unlikely it would fail on CO or HC. Do some research if you don't believe it.

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2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL