Circuit Description

The rear oxygen sensor monitors exhaust gas oxygen content and delivers an input signal to ECM. The ECM uses input signal to determine fuel injection system operation. Code is set when front oxygen sensor signal voltage is .45 volt or more and rear oxygen sensor signal voltage is .45 volt or less under the following conditions:

• Engine coolant temperature is 176°F (80°C) or greater.
• Engine speed of 1500 RPM or greater.
• Accelerator pedal is fully depressed for 2 seconds or more.