In 1981, a diesel engine option was new with a late 1981 availability — this is a 1.8-liter Isuzu unit only available coupled to an Isuzu five-speed. The powertrain is the same as was installed in the Isuzu I-Mark. It was not available with air conditioning. New styled-steel wheels with center caps were offered. and the previous wheel and hubcap design was discontinued. Domestic models received a new computer command control feedback system on gasoline engines. The HO option was discontinued. Electronic spark timing was used on 1981 models in place of mechanical timing advance. A new engine cylinder head design (swirl-port) was introduced to improve low-end torque and fuel economy. The Pontiac T1000 was introduced in the spring of 1981, which shared all body stampings with the Chevette, featuring a chrome center with black-trimmed grille and headlight buckets, as well as standard chrome window trim with black area fill. The T-1000 also has additional fresh-air vents at the outer ends of the dashboard. Power steering was a new option for the Chevette, as well as a 3.36 axle ratio (standard on T-1000 models). The active passenger-restraint system was discontinued. New lighter-weight bucket seats were introduced that lacked much of the lower support of the heavier "panned" seats. A new adhesive-based, thinner windshield seal replaced the lock-ring type.