Checking the signal shape
To speed up the warm-up of the oxygen sensor, the ECM supplies power to the sensor heating elements, except during cold starts and sudden accelerations.
To maintain the air-fuel ratio close to stoichiometric, the ECM uses signals from two sensors
Checking the wiring
With the ignition on, measure the voltage between the contacts of the wire part of the connector and the ground.
| Circuit under test | Nominal voltage |
| Contact 2 - "ground" | 0.45 V |
| Contact 4 - "ground" | B+ |
| Contact 3 - "ground" | Approximately 3.5 V |
1. Sensor "mass"
2. Sensor signal
3. Heater control
4. Heater power supply
Checking the heater
Turn off the ignition and disconnect the sensor connector. Measure the resistance of the heating element with an ohmmeter. Nominal value: 9.0 Ohm (at 20°C).