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Registered
Join Date: May 2002
Location: Santa Barbara, CA
Posts: 4,810
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If PSEN is flatlined you have bus conflicts as the EPROM data outputs will never release the AD bus.
Remove the 8051 and the EPROM from the board and measure resistance of the PSEN line vs GND to check if you have a short. If yes that’s your issue.
If not, just install 8051, power up the DME and verify PSEN has a 1Mhz clock. If not it’s a bad 8051. If yes it’s a bad EPROM.
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1974 Targa 3.6, 2001 C4 (sold), 2019 GT3RS, 2000 ML430
I repair/rebuild Bosch CDI Boxes and Porsche Motronic DMEs
Porsche "Hammer" or Porsche PST2, PIWIS III - I can help!!
How about a NoBadDays DualChip for 964 or '95 993
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