O2S Sensor Heater Monitor (NGC)

Description-  If the O2S sensor (O2S) DTC as well as a O2S sensor heater DTC is present, the O2S sensor heater DTC MUST be repaired first. After the O2S sensor heater is repaired, verify that the sensor circuit is operating correctly.

The voltage reading taken from the O2S sensor are very temperature sensitive. The readings taken from the O2S sensor are not accurate below 300° C (572° F). Heating the O2S sensor is done to allow the engine controller to shift to closed loop control as soon as possible. The heating element used to heat the O2S sensor must be tested to ensure that it is heating the sensor properly. Starting with the introduction on the NGC module the strategy for checking the heater circuit has changed. The O2S sensor heater resistance is checked by the NGC almost immediately after the engine is started. The same O2S sensor heater return pin used to read the O2S sensor heater resistance is capable of detecting an open circuit, a shorted high or shorted low condition.