Main Oxygen Sensor (Federal Models)

Data Trouble Code No. 28 - Main Oxygen Sensor Signal

Detecting Condition
Main Oxygen Sensor (rear) signal is reduced to between 0.35 volts and 0.70 volts for 90 seconds under the following conditions (2 trip detection);
- Engine coolant temperature between 80°C (176°F) and 95°C (203°F).
- Engine speed: 1,500 rpm or more.
- Load driving (ex. A/T in overdrive or M/T in 5th gear, A/C on, flat road, 50 mph)
- Main Oxygen sensor (rear) signal voltage: alternating above and below 0.45 volts.

Trouble Area
^ Main Oxygen Sensor (rear) circuit.
^ Main Oxygen Sensor (rear).

Malfunction Indicator Lamp
Normal Mode On
Test Mode On