SACRAMENTO, CA --- The California Air Resources Board said that it fined Nissan Motor Co. $4.4 million last month for "failing to meet requirements concerning the diagnostic equipment that monitors tailpipe emissions on most of its 2005-2007 models -- more than 450,000 vehicles." However, the automaker has resolved the issues.

"Nissan has been cooperative during this investigation, and we are confident that the design process changes they implemented will prevent future problems," ARB Chair Mary Nichols said. 

On-board diagnostic systems are incorporated into vehicle computers to ensure that tailpipe emissions stay at permissible levels. If a problem is detected, the system turns on a "check engine" light to alert the driver. 

The ARB said it discovered Nissan's problems in 2007 during a routine compliance review. The problems concerned "inadequate monitoring of engine sensors that govern proper fuel system operation and whether monitoring takes place as frequently as required," the agency said. 

Nissan's settlement with the ARB requires the company to pay $3 million to the California Air Pollution Control Fund, $1.2 million to the Environmental Education Initiative, and $200,000 to the National OBD (On-Board Diagnostics) Clearinghouse. 

The Air Resources Board is a department of the California Environmental Protection Agency.