We are currently aware of the following points regarding EOBD / OBDII fault diagnosis:

Audi
Certain models of the Audi A4 and A6 do not appear to have sufficient clearance around the EOBD / OBDII connector to allow connection of most tools. This appears to be a manufacturing design fault on these cars.

Ford
A large number of European Ford cars have been found to support EOBD / OBDII diagnostics back to approximately 1998. Most petrol Ford cars with the EEC-V engine management system are EOBD / OBDII compliant.

Jaguar
A large number of European Jaguar cars have been found to support EOBD / OBDII diagnostics back to approximately 1998.

Peugeot / Renault / Vauxhall
Whilst a 16-pin connector was present on some Peugeot / Renault / Vauxhall cars before January 2001, it appears that they did not support EOBD / OBDII diagnostics until January 2001. The wiring of the earlier connector does not appear to be EOBD / OBDII compliant.

Rover and MG
A large number of Rover and MG cars do not seem to have the Signal Ground pin (pin 5) connected on the diagnostic socket. Diagnostic tools that rely on pin 5 as a circuit ground do not power-up correctly on these cars.

Volkswagen
Certain models of the VW Passat do not appear to have sufficient clearance around the EOBD / OBDII connector to allow connection of most tools. This appears to be a manufacturing design fault on these cars.