This article will show you how to test the upstream oxygen sensor (O2S11) on your 2.0L or 2.4L Chrysler car or mini-van.
The test can be accomplish in a few easy steps and you'll be able to say, “YES, the O2 sensor is BAD or NO, it's OK” before you spend the money and replace it.
To help you navigate this article, here are its main points:
- Important Suggestions and Tips
- Oxygen Sensor Basics
- Oxygen Sensor Test: Inducing a Rich Condition
- Oxygen Sensor Codes Keep Coming Back
- Symptoms of a BAD Oxygen Sensor
- More Test Articles
Important Suggestions and Tips
TIP 1: I've designed this article so that you can use a Generic Scan Tool. You don't need the Chrysler factory scan tool or an expensive professional technician level scan tool to follow the test procedures in this article (Don't have a scan tool? Need a scan tool? Check out my recommendation: Actron CP9580 Scan Tool).
TIP 2: This is an On Car Test of the oxygen sensor on your Chrysler 2.0L, 2.4L vehicle... so you will not be removing it to test it.
Oxygen Sensor Basics
In a nutshell, the job of the pre catalytic converter oxygen sensor is to report back to the PCM that it is either injecting too much fuel (known as a Rich condition), or that it is not injecting enough (known as a Lean condition).
Depending on what the O2 sensor is reporting, the PCM will adjust the amount of fuel it's injecting into the engine.
Here are some more specifics:
If too much fuel is being injected into the engine, the oxygen sensor produces a voltage above 0.500 Volts. This voltage can go as high as 0.900 to 1.0 Volt.
Too much fuel means that the air fuel mixture is Rich and once the PCM knows this, via the O2 sensor, it starts to inject less.
As the PCM starts to inject less fuel.. it may go too far and not inject enough. Here again the O2 sensor saves the day by reporting a voltage that can go as low as 0.050 to 0.100 Volts.
Too little fuel means that the air/fuel mixture is too Lean and the PCM starts to inject more.
This process (of adjusting the amount of fuel being injected) by the PCM, goes on the entire time the engine is running (and if the O2 sensor is working correctly).
All of these oxygen sensor voltages changes can be easily observed with a scan tool in Live Date mode, and this is how I'm gonna' show you how to test them.
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.
To find out what are some of the most common symptoms of a failed oxygen sensor, take a look at the section: Symptoms of a BAD Oxygen Sensor. OK, let's turn the page and let's get testing...
O2 SENSOR TEST: 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).
Alright, this is what you'll need to do:
Start you vehicle and let it idle for about 15 minutes, since you need a warmed up engine to get the O2 sensor to activate (Don't have a scan tool? Need a scan tool? Check out my recommendation: Actron CP9580 Scan Tool).
Connect your scan tool and get to its Live Data mode.
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.
What you should see, if the engine has been idling for about 15 minutes, are 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.
STEP 4 Continued in the next page...