German carmaker Volkswagen has set a 30 November deadline for staff with knowledge about its diesel emissions test cheating to come forward.
Workers who get in touch with internal investigators by then will be exempt from dismissal, according to a letter from VW brand chief Herbert Diess.
US regulators found VW put in software that turned on emissions controls when the car was being tested.
Some 11 million vehicles worldwide are affected by the scandal.
Mr Diess said the offer was being made in the interests of "full and swift clarification".
VW said it would not sack workers for what they might reveal, but they might be transferred to other duties.
"Employees covered by collective bargaining agreements who get in touch promptly, but no later than November 30, 2015... and... may rest assured that the company will waive consequences under labour law such as the termination of employment, and will not make any claim for damages," the letter said.
Last week, Europe's biggest carmaker also admitted to cheating on carbon dioxide emissions certifications.
VW has put aside €6.7bn (£4.7bn) to meet the cost of recalling the diesel vehicles worldwide that were fitted with so called "defeat devices" that circumvented tests for emissions of nitrogen oxides.