How To Test a Chevy Impala Oxygen Sensor

How To Test a Chevy Impala Oxygen Sensor


Over time the 02 sensor in your Chevrolet can become fouled or fail all together. If you own a late model vehicle, there are several oxygen sensors in your car. Depending on the location of these 02 sensors, they will do different things. For instance, the upstream or front oxygen sensor is primarily responsible for your fuel injection. When your front Impala oxygen sensor goes bad, it’s going to cause your Chevy to run poorly.

As your Chevy is running, contaminants in your fuel can lead to the eventual fouling of the Impala oxygen sensor. When this happens to the 02 sensor, otherwise known as the Impala oxygen sensor, it must be replaced. Today I’ll be showing you how to test the primary Impala oxygen sensor in a 2001 Chevy with a 3.4 liter engine in it.

Test Chevy Impala Oxygen Sensor 1

When the Impala oxygen sensor fails in your Chevy, there’s going to be several symptoms that you’ll see. Some of these Impala issues are listed below that stem from a failed oxygen sensor.

Common Impala issues from a failed oxygen sensor

When the primary or upstream Impala Oxygen Sensor goes bad, here’s just a few of the symptoms you’ll see.

  • Bad gas mileage
  • Sluggish performance
  • Impala won’t start
  • Check Engine Light ON

One of the first Chevy Impala issues you will see is of course your OBDII check engine light. This is otherwise known as the OBDII Malfunction Indicator Lamp or MIL. When you see your Chevy Impala service light on, you’ll need to use a OBDII scan tool to read the stored alphanumeric code.

The vehicle we are working on today has a stored OBDII check engine light for the P0131 check engine light. The correct language for this specific code is O2 Sensor Circuit Low Voltage Bank 1 Sensor 1. This trouble code means that your Chevy engine computer is receiving a low voltage signal from your upstream oxygen sensor.

Possible causes to P0131 Impala trouble code

Because the upstream Impala oxygen sensor is sending a low voltage, it’s usually caused by fuel delivery problems. Some of these issues can cause your Impala to throw a P0131 trouble code.

  • Bad fuel pump
  • Poor fuel or contaminated fuel
  • Clogged or leaking fuel injectors
  • Bad MAP sensor or MAF
  • Failing Impala Oxygen Sensor

Impala Oxygen Sensor terminology

Before we being testing your upstream Impala Oxygen Sensor, there’s a few terms you should nail down. Understanding these terms will help you determine what sensor is what on your engine.

  • O2S11 – This sensor refers to the upstream sensor on the Bank 1 side of your Impala engine.
  • Downstream – This refers to the sensor that’s mounted after your catalytic converter.
  • Sensor 1 or Sensor 2 – These terms refer to the primary or Sensor 1, and the downstream or Sensor 2.
  • Catalytic Converter – This is the emissions equipment that’s mounted to your exhaust piping directly after your exhaust headers or the collector to your headers.

Testing your Impala Oxygen Sensor

In order to begin our guide to testing your Impala Oxygen Sensor, you’ll need a digital multimeter. This device will help you determine where the fault is in your Impala oxygen sensor. Once you are ready to begin testing your Impala O2 sensor, you’ll need to locate your problem sensor and unplug it.

Test Chevy Impala Oxygen Sensor 2

Before you begin testing the wiring harness directly, you’ll be using the OBDII scan tool to read what your engine computer is seeing. Because the P0131 OBDII trouble code refers to your Impala oxygen sensor sending a low signal, you’ll check to see what your Impala computer sees real time.

Often times the P0131 check engine light will be accompanied with other codes. If the P0131 trouble code is the only one in your Impala On Board Diagnostic Computer, then all you’ll need is a scan tool to proceed.

In order to test the P0131 Impala trouble code, plug in your OBDII scan tool and scroll to Live Data. The P0131 OBDII trouble code means that your Impala computer sees a voltage from your upstream oxygen sensor that’s below .5 volts. In order to check this, you will be reading the Live Data, or the information that your computer sees real time.

Turn the key to the “ON” position, and you’ll be using the connected OBDII scan tool to read the Live Data information. Scroll to the section where it displays front oxygen sensor information. The field you are looking for is labeled with O2S11. Now that you’ve got the ignition turned to the ON position, and the scan tool connected, you are ready to go.

  1. Start your engine
  2. Allow the engine to warm up

When your cooling fans turn on, the engine is warmed up and ready for testing. The PID you will be reading is the O2S11 field. This is the field that reads the voltage from the upstream Impala Oxygen Sensor.

Look at the PID for the front oxygen sensor. A normally operating oxygen sensor will oscillate between 0.100 Volts and 0.900 volts of signal. If you don’t see this value in the PID field, just make sure you don’t have a value under .5 volts. If the sensor reports a low voltage, or it’s stuck below .5 volts, it’s time for a replacement sensor.

If you do get a reading but it’s not under .5 volts, something else is causing your P0131 trouble code. To test the upstream oxygen sensor, you’ll be disconnecting a vacuum hose that runs to your intake manifold.

Now slowly spray some carb cleaner into the intake manifold. You can also use your left PCV valve hose as well. If your Impala engine stalls out, you’ve sprayed too much. After injecting your engine with some carb cleaner, check your OBDII scan tool again.

Your Impala computer should now report a reading above 0.800 in the O2S11 PID field. Once you are done spraying the engine should slowly burn off the excess fuel in the combustion chamber. Once this happens the PID sensor value will fall back down to a normal range.


If this does not happen, your front Impala oxygen sensor should be replaced. Unscrew the old O2 sensor and install your replacement. You’ll need to use your OBDII scan tool to clear your Impala trouble code.