Tracker 4x2 L4-1590cc 1.6L (1991)
Oxygen Sensor: Testing and Inspection
Chart C-1A
Oxygen Sensor Heater Circuit
CIRCUIT DESCRIPTION:
The Oxygen (O2) has a built in heater. This heater has battery voltage whenever the ignition switch is turned "ON." The heater causes the O2 sensor to
produce a signal to the ECM. This allows for better fuel control during engine warm-up. No codes can be set if the heater portion of the O2 sensor fails.
However, since it is part of the O2 sensor, it is necessary to replace the entire sensor if the heater is found to be faulty.
