The 1976 and later trucks sold in California and almost all 1979 and later trucks have a catalytic converter installed in the exhaust system to aid in the reduction of HC and CO emissions. The only exceptions are some 1979–80 models sold in Canada.
The catalytic converter is a muffler-shaped device located between the exhaust manifold and the muffler. It is filled with beads containing platinum and palladium which, through catalytic action, enables the HC and CO gases to be converted into water vapor (H$SUB2O) and carbon dioxide (CO$SUB2). The converter has a warning system (1976 only), consisting of a thermo sensor inserted into the side of the converter, which monitors temperatures, and a warming light on the instrument panel which lights when the sensor detects converter temperatures exceeding 1,742°F (950°C). The converter should be inspected periodically for cracks, corrosion, and any signs of external burning, and replaced as required.