This tutorial will help you to test the upstream oxygen sensor on your 2.4L Nissan Altima, Xterra or Frontier and/or troubleshoot OBD II codes P0131, P0133.
The upstream oxygen sensor is the one before the catalytic converter and is also known as O2S11.
Contents of this tutorial:
Important Suggestions And Tips
TIP 1: You will need a scan tool to use the testing info in this article. Your scan tool must have Live Data capability since a simple code reader won't help you.
You don't need the Nissan factory scan tool or an expensive professional technician level scan tool to follow the test procedures in this article, since a simple generic scan tool will do just fine (Don't have a scan tool? Need a scan tool? Check out my recommendation: Actron CP9580 Scan Tool Review).
TIP 2: The oxygen sensor test, I'm gonna' show you in this article, is an on-car test, so you do not need to remove it to test it.
Symptoms Of A Bad Oxygen Sensor
The effects of a bad oxygen sensor can be very subtle since they usually do not cause serious drive-ability problems. Here are the most common symptoms:
- The check engine light (CEL) will be illuminated on your instrument cluster.
- The diagnostic trouble codes lighting up the CEL usually are:
- P0131 Upstream Heated Oxygen Sensor (O2S11) Circuit Out Of Range Low Voltage (Bank 1).
- P0133 Upstream Heated Oxygen Sensor (O2S11) Circuit Slow Response (Bank 1).
- Really bad gas mileage.
- Won't pass state mandated emission testing.
Oxygen Sensor Basics
The job of the O2 sensor in your 2.4L Nissan Altima (Frontier, Xterra) is to help the PCM (Powertrain Control Module = Fuel Injection Computer) fine-tune the amount of fuel that it injects into the engine.
If the PCM injects too much fuel, the air/fuel mixture turns Rich. If it doesn't inject enough, the resulting air/fuel mixture is said to be Lean.
The O2 sensor measures how Rich or Lean the exhaust is and reports it back to the PCM.
Here are some more specifics:
- If the PCM injects too much fuel into the cylinders, the air/fuel mixture will turn Rich.
- The oxygen sensor reacts by producing a voltage above 0.500 Volts. This voltage value can go as high as 0.900 - 1 Volts DC.
- When the PCM sees the oxygen sensor voltage above 0.500 Volts, it injects less fuel.
- As the PCM begins to inject less fuel, it may go too far and not inject enough. This causes the air/fuel mixture to turn Lean.
- The oxygen sensor reacts by producing a voltage below 0.500 Volts. This voltage value can go as low as 0.100 Volts DC.
- When the PCM sees the oxygen sensor voltage below 0.500 Volts, it injects more fuel.
- This process (of adjusting the amount of fuel injected) by the PCM goes on the entire time the engine is running.
- A correctly working O2 sensor will produce a voltage that will switch between a Lean and Rich condition several times every few seconds. So, if the voltage output of the O2 sensor stays fixed (when testing it), the O2 sensor has failed.
The cool thing is that you can see these oxygen sensor voltage changes with a scan tool in Live Data mode, and this is how I'm gonna show you how to test them.
TEST 1: Inducing A Rich Condition
To test the oxygen sensor (O2S11), the very first thing you'll do is to induce a Rich condition.
This can easily be done by spraying a little carburetor cleaner into the engine while it's running. My preferred method is to spray carb spray into a vacuum hose.
Once the carb spray 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).
Don't have a scan tool? Need a scan tool? Check out my recommendation: Actron CP9580 Scan Tool Review.
Alright, this is what you'll need to do:
Start your vehicle and let it idle for about 15 minutes. This will allow the engine to warm up and activate the O2 sensor.
Connect your scan tool and get to its Live Data mode.
Scroll down to the PID that's labeled O2S11. This PID will show you the oxygen sensor voltage activity.
You should see the O2 sensor voltage numbers 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.
With the engine running, spray a little carburetor cleaner into a vacuum hose (that has engine vacuum) while you observe your scan tool's display screen.
You're not going to be able to spray carb cleaner into the throttle as the engine is running, because if you were to do this, the engine will die as soon as you disconnect the air duct from it (to spray into it).
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.
You should see the O2S11 voltage values immediately spike to 0.800 to 0.900 Volts. And as long as you're spraying, these voltage numbers should stay there.
Stop spraying carb cleaner into the vacuum hose and let the engine idle for about 1 minute.
The O2 sensor values should come down. Within a few seconds, they should start oscillating between 0.100 Volts to 0.900 Volts.
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 is the correct and expected test result and lets you know that the O2 sensor is reacting to the Rich condition you induced.
The next test is to make sure that the O2 sensor reacts to a Lean air/fuel mixture. Go to: TEST 2: Inducing A Lean Condition.
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.