Sources familiar with the situation have indicated that Volkswagen AG is close to proposing a fix for the 3.0L diesel engines that power Audi and Porsche vehicles included in the emissions cheating scandal. Illicit software used in the motors was determined to include a defeat device that affected emissions readings by manipulating the temperature of the exhaust-cleaning system.

Designed by VW’s Audi division, the 3.0L diesel engine is used in the Audi A6, A7 and A8 sedans, the Q5 and Q7 sport utility vehicles and the Porsche Cayenne and Volkswagen Touareg SUVs. Approximately 85,000 vehicles sold in the U.S. are affected.

While details of the fix are pending finalization of technical details and a review of test results, the sources maintain that making the engines compliant with Environmental Protection Agency regulations will require a software upgrade and possible replacement of the catalytic converter. Any proposed solution will require approval from U.S. regulators.

Volkswagen’s Audi brand has reserved 228 million euros to resolve the emissions issues concerning the 3.0L diesel engines. If approved, sources speculate that the fix will help the brand avoid the possibility of a costly buyback program.