User's Guide

OBDII ECU
Purpose
The OBDII interface is a connector, electrical specification, and protocol used for viewing the
operation and status of a car. It is mandated in all light duty vehicles sold in North America
beginning in 1996, and while the focus of the information it provides is for monitoring the
emissions of Internal Combustion Engines, it has proven to be a handy port for connecting a
variety of aftermarket displays and monitors to a car. Electric Vehicles have no need for
emissions monitoring, so often omit the port from the car, thus making the these aftermarket
devices incompatible. The OBDII ECU capability of the OVMS v3 is used to create a simulated
OBDII port, which can be used to attach many of these aftermarket devices to the car.
Cabling
The cable and OBDII connector are not provided with the OVMSv3 module, and can be built
using the diagram below. In future, a standard cable will be available for this, and this guide
updated when that happens.
DA26
OBDII Female
Signal name
6
14
CAN3-L
16
6
CAN3-H
8
4 & 5
Chassis & Signal Ground
18
16
+12v switched output to HUD/dongle
N.B. Also place a 120 ohm resistor between OBDII pins 14 & 6 for bus termination
OVMS v3 User Guide Page 73 / 86