April 5, 2026: LEMON Manuals is launched! Read the announcement.

Test I

PCM monitors HO2S voltage when AIR pump is enabled. If HO2S voltage drops to a predetermined range, PCM assumes that AIR pump is operational. If HO2S voltage increases to a predetermined range, PCM assumes that AIR pump is disabled. If HO2S voltages are out of range or inconclusive, the diagnostic will proceed to the next test.