I have completed and engine conversion on my 1996 Toyota troop carrier and am attempting to use the Sparkfun ODB2 - Uart board to access CANbus to pickup tacho, oil pressure and H2O temp from the ECU. I am using an ATMEGA and other components that require 5vDC and planned to tap into the VBAT terminal on the circuit board. In preparation I a started with the ODB-DB9 cable and the 12v is supplied on PIN 16 of the ODB2 plug. I checked continuity for each circuit board terminal to the pins in the DB9 socket and found NO connection for the VBAT terminal. All others were fine but NO VBAT connection. The ODB-UART doc suggests there should be so am looking for help.
Looking at the schematic (http://www.sparkfun.com/datasheets/Widgets/OBD-II-UART-v13.pdf), there is a diode in series between pin 9 on the DE-9 connector and the VBAT terminal. Make sure you take that into account when measuring.
/mike
Very nice, thanks Mike.
I guess I had a 50/50 chance at getting my meter polarity right. lol.
Kind regards
Richard
There may be a design or manufacturing defect where the VBAT terminal isn’t connected to the OBD-II pin 16.
Thanks for your reply however in my instance it was a case of mistaken testing for continuity.
The circuit on the VBAT terminal has a blocking diode to protect from reverse voltage polarity and my meter was connected with reverse polarity.
When tested correctly then continuity was fine.
Cheers
Richard
1 Like
It sounds like VBAT isn’t properly connected in your setup. Check if pin 16 (12V supply) is correctly wired from the OBD-II. You might need to manually solder the connection if something’s loose. Alternatively, try connecting an external 12V directly to the VBAT terminal on the board.
Additionally, some vehicles have specific pinout configurations that might differ from standards. Check your vehicle’s documentation or search for similar conversions on forums – you might find someone who’s faced the same issue