In addition to the point reduction for Kenseth, the No. 20 Toyota-car team crew chief Jason Ratcliff was fined $200,000, suspended for six NASCAR points races and will be on probation until Dec. 31. Car owner Joe Gibbs was reduced 50 points as well.
The penalty drops Kenseth from eighth in the drivers' standings to 14th.
NASCAR said Kenseth's car was found to have violated several rules, including one outlining limits on connecting rods. A connecting rod on the No. 20 car was said to have failed to meet weight minimums.
Toyota Racing Development President Lee White, in a statement, said one of the connecting rods on Kenseth's car was about 3 grams less than the 525-gram minimum.
"We take full responsibility for this issue with the engine used by the No. 20 Joe Gibbs Racing team this past Sunday in Kansas," White said.
"JGR is not involved in the process of selecting parts or assembling the Cup Series engines. It was a simple oversight on TRD's part and there was no intent to deceive, or to gain any type of competitive advantage."
Joe Gibbs Racing officials said they plan to appeal the ruling.