Code 28 (Except GS300 Calif.)

Condition is: main oxygen sensor signal voltage is reduced to 0.4-0.7 volt for 90 seconds with the following conditions. Engine temperature 158-195°F (70-91°C), engine speed more than 1500 RPM and engine under load. Probable cause: defective main oxygen sensor (rear sensor on GS300 and SC300 or right bank sensor on ES300).