20240813
Adapter from rear DLC3 (DLC3 No. 2) to a "generic" OBDII dongle that can read CAN on the standard OBDII socket pins.

Standard OBDII pinout:
CANH = 6
CANL = 14
12v + battery (unswitched) = 16
Chassis Ground = 4
Signal (shield) Ground = 5

(lots of others)

DLC3 No.2 CAN/power pinout:
CANH = 6 (no change)
CANL = 14 (no change)
12v + = N/A
Chassis Ground = N/A
Signal (shield) Ground = 12

DLC3 No.2 TPD/ethernet pinout:
TX- = 1
TX+ = 9
RX- = 3
RX+ = 22

As there is no power/ground at DLC3 No. 2, to power a CAN diagnostic dongle we must bring 12v + and - from a separate source to the dongle connector.
Connect DLC3 No. 2 #12 to dongle connector #5

References:
garygid's post on adapter harness for early Model S:
https://teslamotorsclub.com/tmc/threads/logging-multiple-can-buses-to-pc-with-my-can-do-program.64292/#post-1410131
1. Ground on TDC pin 9                         - goes go OBD pin 4
2. Power ("12v", usually more) from TDC pin 10 - goes to OBD pin 16
3. CAN3 High pin 1                             - goes to OBD pin 6
4. CAN3 Low pin 6 (which is adjacent to pin 1) - goes to OBD pin 14

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