I also have a CA 1991 190E 2.3 with a check engine light on. I cannot get the test LED to do anything. The service info says that a condition is that the check engine light must be off. How can I do that without also clearing the codes? Thanks.

Steve

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'91 MB 190E 2.3
'08 RAV4 Ltd 3.5
'83 Lazy Daze m'home 5.7