TEST 1: Manually Creating A Rich Condition To Test The O2 Sensor

Creating A Rich Condition. How To Test The Upstream Oxygen Sensor (1.6L Honda Civic)

The two most common type of oxygen sensor failures are the sensor not reacting fast enough to changes in the air/fuel mixture or not reacting at all.

The cool thing is that you and I can easily check to see if this is happening (or not) by simply inducing a rich condition and checking to see if the O2 sensor reacts to it (or not).

The fastest and easiest way to induce a rich condition is by spraying a little starting fluid into the engine while it's running. My preferred method is to spray starting fluid into a vacuum hose.

Once the starting fluid hits the engine cylinders, you'll get an instant rich condition which will make the O2 sensor respond by producing its maximum voltage (0.900 Volts +) and you'll be able to see this on your scan tool (in Live Data mode).

Alright, this is what you'll need to do:

  1. 1

    Start your Honda and let it idle for about 15 minutes, since you need a warmed up engine to get the O2 sensor to activate.

    Connect your scan tool and get to its Live Data mode.

  2. 2

    Once you're in Live Data mode, scroll down to the PID that's labeled O2S11. This PID will show you the oxygen sensor voltage activity.

  3. 3

    You should see The voltage numbers of the O2 sensor moving between 0.100 and 0.900 Volts constantly.

    If the voltage value stays fixed, don't worry about this yet, continue to the next step.

  4. 4

    With the engine running, spray a little starting fluid into a vacuum hose (that has engine vacuum) while you observe your scan tool's display screen.

    If you spray too much, there's a good chance that the engine will stall. If it happens, just restart the engine and repeat the step and spray less starting fluid.

  5. 5

    The oxygen sensor should immediately report 0.800 to 0.900 Volts, as you spray the short bursts of starting fluid into the vacuum hose. And as long as you're spraying (without the engine stalling), the voltage should stay there.

  6. 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: O2S11 voltage numbers spiked to 0.900 Volts when you sprayed carb spray into the vacuum hose -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.

For more info on this, go to the section: Oxygen Sensor Codes Keep Coming Back.

CASE 2: O2S11 voltage numbers DID NOT spike to 0.900 Volts when you sprayed carb spray into the vacuum hose -This confirms that Bank 1 Oxygen Sensor 1 is no longer working. You can replace the oxygen sensor.

TEST 2: Manually Creating A Lean Condition To Test The O2 Sensor

In this section we will induce a lean air/fuel mixture to see if the oxygen sensor reacts to it and reports it. We'll accomplish this lean air/fuel mixture by disconnecting a large vacuum hose.

By creating a large intake manifold vacuum leak (with the engine running), the air/fuel mixture will instantly become lean. This will cause the oxygen sensor to produce its minimum voltage (between 0.100 to 0.200 Volts). We'll be able to see this low voltage reading on the scan tool's display.

The hose we'll disconnect is the one that connects the intake manifold to the vacuum brake booster.

Alright, here are the test steps:

  1. 1

    Crank and start your 1.6L Civic's engine. Let the engine run for about 15 minutes.

    With your scan tool still connected to the diagnostic link connector (DLC) go to it's live data function. Now, scroll down to the PID labeled: O2S11.

  2. 2

    Disconnect the vacuum hose with the engine running as you watch the reading of the O2S11 PID on your scan tool's display.

    If the engine is stalls, simply restart it and start from step 1 again (and disconnect the hose just a little this time).

  3. 3

    As you are letting air enter the brake booster's vacuum hose, the voltage reading of the O2S11 PID should decrease to about 0.100 to 0.200 Volts. And while the vacuum hose is letting ambient air into the intake manifold, the voltage should remain at about 0.100 to 0.200 Volts.

  4. 4

    Reconnect the brake booster's hose and stop the vacuum leak. The voltage reading should now start to move up and down between 0.100 to 0.900 Volts.

Let's take a look at what your test results mean:

CASE 1: The voltage dropped to 0.100 Volt as you opened the brake booster's vacuum hose: This tells you that the oxygen sensor is working well since it can react to a lean air/fuel mixture and report it.

Now, if the oxygen sensor passed the test in TEST 1 and passed this test (TEST 2), then you can conclude with certainty that the oxygen sensor is working properly and it doesn't need to be replaced. If the computer is still accusing it of being defective, take a look at this section: Oxygen Sensor Codes Keep Coming Back.

CASE 2: The voltage DID NOT drop to 0.100 Volt as you opened the brake booster's vacuum hose: This test result tells you that the oxygen sensor is defective since it can not react to a lean air/fuel mixture. Replacing the O2 sensor will solve the issue.