Hi John,

Your daughter sounds pretty savvy already. Since you swapped OBD units, I'd assume any corroded connections got burnished clean in the process.

You can see that OBD (131 in diagrams) socket 2 goes to FI ECU pin 12, which is ground that the ECU controls to make the LED blink. The +side of the LED gets its Key On +12V via 131 pin 4 and the Ignition switch (3/15).

I guess you two can ring out that wire to ECU 12, but if it's failing internally I wouldn't be in a hurry to junk it as long as it's OK otherwise.

P.S. You're right about the mislabeling (196) on the REX ICU. I noticed it too, but didn't want to add to the mix.


--
Bruce Young, '93 940-NA (current), 240s (one V8), 140s, 122s, since '63.