Chrysler purchased AMC in 1987, and by the 1991 model year adapted their own engine control electronics to replace the original Renix systems used with the 2.5 L and 4.0 L engines. Power and torque in both engines improved as a result, with the four-cylinder having an additional 9 hp and 8 lb⋅ft and the six-cylinder improving by 1 lb⋅ft and 13 hp. The 4.0 L was badged "High Output" thereafter. As a result of the power improvements the Aisin-Warner automatic transmission's output shaft was changed from 21 splines to 23, and the "Power-Comfort" switch was deleted. The four-cylinder was no longer available with the automatic in 1991 and 1992.