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Catalyst Monitor (Good Catalyst)

WARNING: This page is about a different variant/trim than selected.

A good TWC catalyst will show a very active output voltage on the pre-catalyst heated oxygen sensor (1). A good catalyst, 95 percent hydrocarbon conversion, will show a relatively flat output voltage on the post-catalyst heated oxygen sensor (2).

Fig 1: View Of Catalyst Monitor (Good Catalyst)

Courtesy of GENERAL MOTORS CORP.