The Environmental Protection Agency is proposing that onboard diagnostic (OBD) devices be used to monitor the emissions-control systems used on 2010-compliant heavy-duty engines. The OBD requirement would apply to on-highway vehicles weighing more than 14,000 lb.

Under EPA's proposal, OEMs would be required to install the devices, which would alert vehicle operators to any problems with the emissions control system.

In addition, the proposal would revise some of the existing OBD requirements for diesel engines used in heavy-duty vehicles under 14,000 lb.