Here is a picture of the board from my 91, made in 1990. It looks nearly identical to the one you pictured:



I see a couple small differences though.

I checked the two 22nF caps and according to my meter they were each about 26nF.

Did you do any checks on the resistors in the coding plug?

Also, I wonder why all the caps are "high" voltage? Surly the module runs at 5-12v internally?

-Jason

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1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.