Code 21 - Main Oxygen Sensor Signal

Data Trouble Code No. 21 - Main Oxygen Sensor Signal

Detecting Condition
Main Oxygen Sensor voltage is reduced to between 0.35 volts and 0.70 volts for 60 seconds under the following conditions (2 trip detection):
- Engine Coolant Temperature 80°C (176°F) or more.
- Engine Speed 1,500 rpm or more.
- Load driving i.e., transmission in overdrive or fifth gear, air conditioning ON, 80 km/h (50 mph).
- Main Oxygen Sensor voltage alternating above and below 0.45 volts.

Trouble Area
- Main Oxygen Sensor circuit.
- Main Oxygen Sensor.

Malfunction Indicator Lamp
Normal Mode ON
Test Mode ON