(Ridgefield, WA) -- The co-owner of a Ridgefield diesel truck maintenance and sales company has pleaded guilty to tampering with pollution control software. Fifty-year-old Sean Coiteux's company would charge up to two-thousand dollars to modify a diesel truck to eliminate pollution controls. They deleted the software on 375 trucks and made 538-thousand dollars. It improves power and performance, but causes the engine to spew 12-hundred times the amount of pollution. Coiteux's wife Tracy Coiteux is also charged and set for trial in May. The company's service manager pleaded guilty. Prosecutors are recommending Coiteux be sentenced to no more than six months in prison, but the judge can impose any sentence allowed by law.