Source: Manufacturer PR

From Jim Campbell GM US Vice President Performance and Motorsports

“Chevrolet is disappointed that Team Penske violated an NTT INDYCAR Series rule resulting in the disqualification of the No. 2 car and No. 3 car and the penalty to the No. 12 car from the St. Petersburg Grand Prix. We support INDYCAR’s decision and action.” 

A little more in-depth via a Chevrolet spokesperson:

“The code that modifies the INDYCAR push-to-pass MyLaps transponder signal resides on the Cosworth Central Logger Unit (CLU) and is the responsibility of the team. Chevrolet has no input or responsibility for the software or operation of the CLU. The engine responds to the output of the CLU.”