How To Test The Oxygen Sensor (O2S11) (Mitsubishi 1.8L, 2.4L)

In this article, I'll show you how to test the oxygen sensor on your 1.8L, 2.4L Mitsubishi (Chrysler, Dodge) vehicle.

Your vehicle comes equipped with two oxygen sensors. One is called an upstream oxygen sensor, since it's located before the catalytic converter and the other is know as the downstream oxygen sensor and is located after the catalytic converter. This article focuses on the upstream oxygen sensor (O2S11).

To help you navigate this article, here are its main points:

  1. Important Suggestions and Tips
  2. Symptoms Of A BAD Oxygen Sensor
  3. Oxygen Sensor Trouble Code Basics
  4. Oxygen Sensor Basics
  5. Test 1: Inducing a Rich Condition
  6. Oxygen Sensor Codes Keep Coming Back
  7. More Test Articles

Important Suggestions and Tips

TIP 1: You'll need to use a scan tool that has Live Data capability for the O2 sensor test I'm gonna' show you in this article.

In case you wondering, you don't need the factory scan tool or an expensive professional technician level scan tool to follow the test procedures in this article (if you don't have a scan tool and you need to buy one, check out my recommendation here: Actron CP9580 Scan Tool Review -at troubleshootmyvehicle.com).

TIP 2: You will not be removing the O2 sensor to test it, since the O2 sensor test is done with it in place and in action as the engine runs.

Symptoms Of A BAD Oxygen Sensor

A failed oxygen sensor doesn't cause major/severe engine performance issues. You'll usually see one of several of the following symptoms:

  1. Check engine Light is illuminated on your instrument cluster with one of the following Codes:
    1. P0132: Heated Oxygen Sensor Circuit High Voltage (Sensor 1).
    2. P0133: Heated Oxygen Sensor Circuit Slow Response (Sensor 1).
    3. P0134: Heated Oxygen Sensor Circuit No Activity Detected (Sensor 1).
    4. P0135: Heated Oxygen Sensor Heater Circuit (Sensor 1).
  2. BAD gas mileage. A malfunctioning, slow, or non-operating oxygen sensor will have a negative impact on your vehicle's fuel consumption.
  3. Emissions will be higher, which means your vehicle will pollute more.

Oxygen Sensor Trouble Code Basics

If you've been wondering exactly what the heck each diagnostic trouble code means in lay man's terms, below I've added a few words beyond the official description of the code:

P0133: Heated Oxygen Sensor Circuit High Voltage (Sensor 1)

  1. This tells you that the oxygen sensor before the catalytic converter is reporting a high voltage of 4.5 Volts or more when the engine is in operation.
  2. When the oxygen sensor's output signal is viewed with a scan tool (in Live Data mode), the scan tool will report 4.5 Volts or higher for O2S11.
  1. With the help of the oxygen sensor test in this article, you'll be able to confirm if the O2 sensor output voltage is really at 4.5 Volts or higher.
  2. In my experience, the times I've seen this problem is when the oxygen sensor's wires have melted together and thus shorting to each other or a universal oxygen sensor was used and the wires were not spliced to the correct ones (of the old connector).

P0132: Heated Oxygen Sensor Circuit Slow Response (Sensor 1)

  1. This tells you that the oxygen sensor before the catalytic converter is switching between a Lean and Rich Condition too slowly.
  2. This diagnostic trouble code (DTC) usually always means that the O2 sensor is old and ready to retire.
  3. With the help of the oxygen sensor test in this article, you'll be able to confirm if the O2 sensor is worn out and not responding fast enough.

P0134: Heated Oxygen Sensor Circuit No Activity Detected (Sensor 1).

  1. This tells you that the O2 sensor's output does not cross 0.5 Volts after the engine has warmed up (operating temperature above 169° F [76° C]).
  2. This most always indicates that the O2 sensor has completely worn out and is dead.
  3. With the help of the oxygen sensor test in this article, you'll be able to confirm if the O2 sensor has gone on to the ‘big gig in the sky’.

P0135: Heated Oxygen Sensor Heater Circuit (Sensor 1).

  1. This tells you that the PCM has detected the heater inside the O2 sensor has gone BAD.
  2. 99.9% of the time, this indicates that you need a new oxygen sensor (because its internal heater has fried).