What is Subaru OBD?
OBD stands for On Board Diagnostics. It refers to a protocol for communication with the ECU.
Why do I care if my car is OBD1 vs. OBD2?
If your car is OBD1 it means that there is a basic level of communication with the ECU that can only be accessed by a Subaru scan tool called a SSM (Subaru Select Monitor). OBD1 is essentially a very rudimentary way to tell you there is a general problem. Normally to see what an issue is the procedure is to plug in the test mode connector and your check engine light flashes in a series which represents a code. You can also pull these codes out of stored memory for when the light comes and goes via the Read Memory Connectors. OBD2 is a more advanced communication protocol that can give more specific information that tells much more about the nature of the issue. Any standard scan tool can plug into the OBD2 and read the codes. It also means you can communicate with the ECU and get more advanced live data from it.
If I Want to Upgrade, How Do I Switch from OBD1 to OBD2?
The communication protocol is hard wired into the ECU, so to upgrade to OBD2 you have to use an OBD2 equipped ECU. Generally as a byproduct of this you would also have to do an engine swap because the requirements for the engine that goes with an OBD2 ECU is going to be different than the engine that goes with an OBD1 ECU.
Can I Switch from OBD2 to OBD1?
Yes you can but we do not recommend it. Since you are down grading the On Board Diagnostics communication type, you can no longer pass emissions or SMOG because a standard scan tool can no longer read it . There is no way around this except for changing out the ECU to an OBD2 compatible ECU.
Is there an OBD3?
Well, sort of. With CANBUS equipped cars the OBD2 port has more capabilities because the communication language is more advanced. It's the same basic idea as OBD2 but since the data is coming from the ECU through a different type of connection (CAN), it is faster and can send more information at one time.