Canadian car, 300K kms approx.

Recent fuel consumption around 12.5 MPG (18 litres per 100 km). Replaced 02 sensor after finding blink codes 11,13 on Socket 8. Replaced fuel pressure regulator on fuel rail because I though i could smell gas in there. Fixed a post CAT exhaust leak.

If anything, fuel consumption is worse! I'm unable to retrieve codes on Socket 3, which looks like the next place to go. When I hook up my home-brew reader, I get a steady light. Looks like Socket 3 is fully or partially grounded already.

This car has the 16 socket interface. It also has an on-board button and LED for the DM Socket 3, but this does not appear to work. May be related to the short to ground?

Any ideas for the fuel consumption or how to get codes out of Socket 3?

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Additional:
Wiring harness replaced by PO some years ago; have receipt
Throttle body recently replaced with a newer unit (2006?)
Have a bad OVP and waiting on a part shipped from US
Constant ABS light, due to bad OVP, probably
Brakes checked for dragging
Car otherwise runs well, idles smooth, holds steady at 80-85 C, good power, minimal oil leaks.