The recently published Supplement 6 to ECE Regulation 83.05 introduces revised requirements for the on-board diagnostic (OBD) systems fitted to bi-fuel vehicles (i.e. vehicles which can operate on both petrol and liquefied petroleum gas (LPG) or on both petrol and natural gas (NG)).
When the requirements for OBD systems were first introduced into ECE Regulation no. 83, the technology to allow the implementation of OBD systems on bi-fuelled vehicles was not fully developed. Therefore, the OBD system requirements originally included in ECE 83 permitted certain exemptions, known as "allowed deficiencies", for bi-fuel vehicles.
With the implementation of Supplement 6 to ECE 83.05, which came into force on 2nd February 2007, these exemptions have been removed and new requirements for the OBD systems of bi-fuel vehicles have been introduced in their place. These new requirements ensure that the OBD systems for bi-fuel provide an equivalent level of performance to the OBD systems for mono-fuel vehicles, but allow bi-fuel vehicle manufacturers more flexibility in their OBD system design. For instance, the new requirements permit bi-fuel vehicles to be fitted with two separate OBD systems; one system for when the vehicle is being operated on petrol and one for when the vehicle is being operated on gaseous fuel.