TEST 2: Manually Creating A Rich Condition To Test The O2 Sensor
If in TEST 1 your test result indicated that the front O2 sensor is stuck below 0.5 Volts (indicating an unhealthy continuous lean condition) or the signal moved up/down but you want to check it's performance, then the next step is to induce a rich condition.
We'll induce this rich condition by spraying starting fluid into the throttle body as the engine runs and as the multimeter is connected to the oxygen sensor's signal wire (so that we can see the result the O2 sensor will report).
If the sensor is good, as soon as the starting fluid has left the can and entered the engine, it should immediately report a voltage near 0.9 to 1 Volt DC.
If the sensor is too slow (and thus in need of replacement), it will slowly report around 0.7 to 0.8 Volts DC.
If the sensor is bad, it will not respond with a voltage increase.
NOTE: Your multimeter must remain connected to the O2 sensor wire as from the previous test.
Alright, this is what you'll need to do:
- 1
Crank and start the engine. Let it run for about 15 minutes to get the O2 sensor to activate.
Once the engine has warmed up, turn it off and remove the air duct connected to the throttle body. - 2
Restart the engine and let it run for one minute at 2000 RPMs (to get the O2 sensor to activate once again).
- 3
Let the engine return to idle (after the minute is over) and observe your multimeter's O2 sensor voltage readings. IF the 02 sensor is OK, you should see the voltages moving between 0.200 Volts and 0.900 Volts.
If the voltages are not moving between 0.100 and 0.900 Volts, don't worry about it just yet, continue on to the next step. - 4
With the engine running, spray a little starting fluid (or carburetor cleaner) into throttle body while you observe your multimeter's display screen.
If you spray too much, the engine will stall. If this happens to you, just restart the engine and repeat the step and spray less carb cleaner spray. - 5
As you spray some short burst of starting fluid or carb cleaner into the throttle body, you should see the O2 sensor voltage numbers mediately spike to 0.800 to 0.900 Volts. And as long as you're spraying, these voltage number should stay there.
- 6
When you stop spraying, the O2 sensor values should come down and within a few seconds, they should start oscillating between 0.100 Volts to 0.900 Volts.
OK, the test is done, let's take a look at what your test results mean:
CASE 1: O2 sensor voltage numbers spiked to 0.900 Volts when you sprayed carb spray into the throttle body. This tells you that the oxygen sensor is OK at this point in time. It does not need to be replaced, since whatever's causing the PCM to think it's fried is something else.
CASE 2: O2 sensor voltage numbers DID NOT spike to 0.900 Volts when you sprayed starting fluid (or carb spray) into the throttle body. This confirms that oxygen sensor is no longer working. You can replace the oxygen sensor.
TEST 3: Manually Creating A Lean Condition To Test The O2 Sensor
If in TEST 1 your test result indicated that the front O2 sensor is stuck above 0.5 Volts (indicating a continuous rich condition) or the signal moved up/down but you want to check it's performance, then the next step is to induce a lean condition.
We'll induce this Lean condition by removing the PCV valve from the valve cover as the engine runs and as the multimeter is connected to the oxygen sensor's signal wire (so that we can see the result the O2 sensor will report).
If the sensor is good, as soon as PCV valve is disconnected, it should immediately report a voltage around 0.5 to 0.2 Volt DC.
If the sensor is too slow (and thus in need of replacement), it will slowly report around 0.5 to 0.2 Volt DC.
If the sensor is bad, it will not respond with a voltage decrease.
NOTE: Your multimeter must remain connected to the O2 sensor wire as from the previous test.
OK, these are the test steps:
- 1
Start and let the engine run for about 15 minutes to get the O2 sensor to activate.
- 2
Observe your multimeter's O2 sensor voltage readings. IF the 02 sensor is OK, you should see the voltages moving between 0.200 Volts and 0.900 Volts.
If the voltages are not moving between 0.100 and 0.900 Volts, don't worry about it just yet, continue on to the next step. - 3
With the engine running, remove the PCV valve from the valve cover while you observe your multimeter's display screen.
- 4
You should see the O2 sensor voltage numbers mediately drop to 0.1 to 0.2 Volts. This drop will be momentary because the PCM will start to compensate by injecting more fuel.
- 5
Connecting the PCV valve should stop the voltage drop and within a few seconds, they should start oscillating between 0.100 Volts to 0.900 Volts.
OK, the test is done, let's take a look at what your test results mean:
CASE 1: O2 sensor voltage numbers drop to 0.200 Volts or less when you removed the PCV valve from the valve cover. This tells you that the oxygen sensor is OK at this point in time. It does tell you that there's a problem causing a rich condition.
CASE 2: O2 sensor voltage numbers DID NOT drop to 0.200 Volts or less when you disconnected the PCV valve. This confirms that oxygen sensor is no longer working. You can replace the oxygen sensor.
More 1.6L Toyota Diagnostic Tutorials
You can find a complete list of 1.6L Toyota tutorials in these two indexes:
Here's a small sample of the tutorials you'll find in the index:
- How To Do A Cylinder Balance Test (1.6L Toyota Corolla).
- How To Test The Throttle Position Sensor (1.6L Toyota Corolla).
- TPS Idle Switch Multimeter Test (1.6L Toyota Corolla).
- How To Test Engine Compression (1.6L Toyota Corolla).
- How To Test The Fuel Injectors (1.6L Toyota Corolla).
If this info saved the day, buy me a beer!
