1. Open the hood and locate the oxygen sensor. It's usually located after the catalytic converter, where the exhaust exits the engine.
2. Identify the electrical connector that connects to the oxygen sensor.
3. Disconnect the electrical connector.
4. Use a voltmeter to check for voltage at the connector terminals.
a) For heated oxygen sensors:
- You should get a reading of around 12 volts on one of the terminals. This voltage is supplied by the engine control unit (ECU).
- The other terminal should show ground continuity (0 volts) when connected to a good chassis ground.
b) For unheated oxygen sensors:
- You should get a reading of around 0.5–0.9 volts on one of the terminals.
5. If you don't get the correct voltage readings, it indicates a problem with the wiring, connector, or oxygen sensor itself.
2. Check the Sensor Signal:
1. Reconnect the oxygen sensor electrical connector.
2. Start the engine and let it reach operating temperature.
3. Use an oxygen sensor multimeter or scan tool to monitor the oxygen sensor's output voltage on the wiring connector.
- Oxygen sensor output should fluctuate between around 0.1–0.9 volts for heated oxygen sensors and between 0.1–1.0 volts for unheated ones.
4. Drive the car for a short while and observe the voltage readings.
5. If the oxygen sensor output does not change or remains constant and does not fluctuate, the sensor may be faulty or the fuel mixture is too rich or lean.
3. Check for Exhaust Leaks:
Exhaust leaks near the oxygen sensor can affect its readings. Check for leaks around the oxygen sensor and exhaust system components. If there are any leaks, they should be repaired before testing the oxygen sensor again.
4. Replace if Necessary:
If the oxygen sensor is found to be faulty, you'll need to replace it. Replacing the oxygen sensor typically requires basic hand tools and limited experience. Consult the vehicle repair manual or online guides for specific instructions for your Toyota Echo.
After replacing the oxygen sensor, clear any trouble codes from the ECU and take the vehicle for a test drive to see if the problem is resolved.
