WS6 Oxygen sensor on vehicle

1999 Mazda Capella

The O2 sensor is located in the engine bay just on the exhaust manifold outlet.

It is a zirconia switching sensor and it has 3 wires:

1. Power - White

2. Ground - Grey

3. O2 signal

After back probing the the signal wire and connecting an oscilloscope, I got an ok signal.

I revved the engine at 2500rpm for about a minute so it would go into closed loop.

This is the pattern that I got.

Peak voltage is 0.8v and lowest voltage is 0.2v. So average voltage would be 0.5v.

Cross counts the signal has in 10 seconds is 10. So it is cycling normally.

Let the engine warm up and enter closed loop so you see a normal cycling pattern. Let the RPM come down to idle.

Highest voltage: 0.8v

Lowest voltage: 0.2v

Average voltage: 0.5v

Cross counts in 10 seconds: 8

Signal status: Cycling normally

Rev up engine so it goes rich. Record results. The signal should go above 0.85v.

Highest voltage: 1v

Signal status: Cycling normally

Make this sensor go lean. Rev up the engine then suddenly decelerate. The signal should go below 0.2v.

Lowest voltage: 0v

Signal status: Cycling normally

Measure the response time. Time how long it takes to go from lean to rich. Voltage should go from below 0.2v to above 0.8v in less than 100ms.

Time: 60ms

Status: slightly slow.

O2 sensors are one of the most important signals on a vehicle. Without it, your vehicle could be running inefficiently and uneconomically, and could cause the engine to fault since the ECU would be missing out on a lot of important data to ensure the vehicle is running in optimum condition.

Zirconia switch sensors are more common since they are cheaper to manufacture. They also switch fast and can withstand high temperatures.

When rich O2 ions from exhaust pass through the sensor, electrons start to flow so you get a higher voltage.