Toyota Yaris Oxygen Sensor – Check Engine Light Keeps Coming On

If the check engine light continues to come on despite replacing the oxygen sensor twice, there could be a few potential reasons for the recurring issue:

Wiring o r Connector Issues: One possibility is a wiring issue o r a loose connector in the oxygen sensor circuit. Over time, wires can wear out, get corroded, o r become loose, which could cause the sensor to malfunction even after replacement. Inspect the wiring and connectors to ensure they are secure and in good condition.

Faulty o r Incorrectly Installed Sensors: Its possible that the replacement oxygen sensors are faulty o r not the correct type for your vehicle. Double-check that youre using the right sensor for your specific make and model. Also, ensure the sensor was installed correctly.

Exhaust Leaks: An exhaust leak near the oxygen sensor could lead to incorrect readings, causing the check engine light to come back on. Check for any leaks in the exhaust system, especially around the area where the oxygen sensor is located.

Fuel System o r Engine Issues: Sometimes, problems with the fuel system like a clogged fuel injector o r a malfunctioning fuel pressure regulator o r other engine components can lead to issues with the oxygen sensor. These problems can affect the air-fuel ratio, causing the sensor to send incorrect readings.

Engine Control Module ECM Issues: If the ECM is malfunctioning o r if theres a software issue, it might be misinterpreting the sensors readings. This would require further diagnosis to determine whether the ECM is faulty and needs to be replaced o r reprogrammed.

Aftermarket Parts: If youre using aftermarket oxygen sensors, they might not be as reliable o r durable as the original ones, which could lead to frequent failures.

To resolve the issue, you can try to clear the codes after checking and fixing any wiring o r installation problems. If the problem persists, a more in-depth inspection of the exhaust system, fuel system, and ECM might be necessary. If youre not comfortable with advanced diagnostics, it would be wise to consult a mechanic.