Oxygen Sensor (O2)
Faults in oxygen sensor circuit may set Code 33. To test system, see CODE 33 (and/or CODE 53) diagnostic procedures in appropriate G - TESTS W/ CODES article in the ENGINE PERFORMANCE section below.
To test HEATER element of Heated Oxygen Sensor (HO2S), check resistance between outer 2 terminals of 3-wire connector. If resistance is not 3-1000 ohms, replace sensor.