Monitor Description
The air fuel-ratio (A/F) sensor varies its output voltage in proportion to the air-fuel ratio. Based on the output voltage, the ECM determines if the air-fuel ratio is RICH or LEAN and adjusts the stoichiometric air-fuel ratio.
The ECM also checks the fuel injection volume compensation value to check if the A/F sensor is deteriorating or not. The output voltage variation, known as locus length, should be high when the air-fuel ratio fluctuates.
When the A/F sensor response rate has deteriorated, the locus length should be short.
The ECM concludes that there is a malfunction in the A/F sensor when the locus length is short and the response rate has deteriorated.