Frequently Asked Questions - On-Board Diagnostics (OBD) 1 & 2

1. What is OBD?

OBD means On-Board Diagnostics. This is a set of guidelines that are implemented within the electronics of the car.

2. What's the difference between OBD1 and OBD2?

OBD1 and OBD2 are two different revisions, and naturally OBD2 progressed from OBD1. Being a development of OBD1, OBD2 has better control algorithms and is standardised across many different cars.

When the OBD requirements changed, it caused the ECUs to be revised by VW in order to fall inline with the new specifications.

3. How do I know which my car has?

The main physical differences between the two standards are the intake manifold, the throttle body, the wiring loom and of course the software within the ECUs are completely different.

There are many ways to tell which your car has, however the ECU number is probably the most definitive.

OBD1 ECU part number will be 021 906 258 ?? and a OBD2 will be 021 906 256 ??. This is found on the label on the outside of the ECU case.