Testing the oxygen sensor (commonly referred to as O2 sensors) on your Ford 4.6L, 5.4L car (pick up, SUV) is not that hard to do.
Since oxygen sensor are not cheap and sometimes the PCM (Powertrain Control Module = Fuel Injection Computer) accuses them of being bad when they aren't, testing them (to make sure they're really bad) is a good idea and this article will help you.
Since the Ford 4.6L, 5.4L Engines have four oxygen sensors, this article concentrates on testing the two that are before the catalytic converter (O2S11 and O2S21).
Contents of this tutorial:
Important Suggestions And Tips
TIP 1: To take advantage of the testing info in this article, you'll need a scan tool. This scan tool must have Live Data capability. Now, you don't need the Ford factory scan tool since I've written this article for use with a generic scan tool (Don't have a scan tool? Need a scan tool? Check out my recommendation: Actron CP9580 Scan Tool).
TIP 2: If you have several diagnostic trouble codes, which are not oxygen sensor related (for example, you have a MAF sensor code along with oxygen sensor codes), you need to diagnose the non-oxygen sensor codes first.
This is important, since there's a good chance that the component (that's causing the non-oxygen sensor code) has failed and is causing the PCM to think (erroneously) that the oxygen sensor or oxygen sensors have failed too, when they haven't.
TIP 3: The testing procedure I'm gonna' show you here is done with the oxygen sensors in action, which means that you'll be testing them with the engine running. Therefore, take all necessary safety precautions and think safety all of the time.
TIP 4: If you need to test an oxygen sensor heater circuit problem (Codes: P0135, P0141, P0155, P0161), you can find the article here: Testing Diagnostic Trouble Codes: P0135, P0141, P0155, P0161.
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 and one or several of the following diagnostic trouble codes will stored in the PCM's memory:
- P0131 Upstream Heated Oxygen Sensor (HO2S11) Circuit Out Of Range Low Voltage (Bank 1).
- P0133 Upstream Heated Oxygen Sensor (HO2S11) Circuit Slow Response (Bank 1).
- P0151 Upstream Heated Oxygen Sensor (HO2S21) Circuit Out Of Range Low Voltage (Bank 2).
- P0153 Upstream Heated Oxygen Sensor (HO2S21) Circuit Slow Response (Bank 2).
- Really bad gas mileage.
- Won't pass state mandated emission testing.
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:
P0131: Upstream Heated Oxygen Sensor (HO2S11) Circuit Out Of Range Low Voltage (Bank 1).
- This diagnostic trouble code (DTC) indicates that the upstream oxygen sensor for Bank 1, is producing a negative voltage (somewhere between 0 and -1 Volts [negative 1 V]).
- The normal voltages that the O2 sensor should produce are between 0.100 to 1 Volt DC and these are in the positive numbers range. So, if the sensor is producing a negative voltage value, there's something wrong.
- You'll be able to verify if the O2 sensor is really outputting such voltage numbers with your scan tool (and you'll see how later in the article).
P0133: Upstream Heated Oxygen Sensor (HO2S11) Circuit Slow Response (Bank 1).
- This diagnostic trouble code (DTC) is letting you know that the upstream oxygen sensor for Bank 1 is switching between a Rich and Lean condition very slowly (lazily).
- This DTC usually indicates that the oxygen sensor (O2S11) is too old and ready to retire. With the help of this test article, you'll easily be able to confirm if this is the case.
P0151: Upstream Heated Oxygen Sensor (HO2S21) Circuit Out Of Range Low Voltage (Bank 2).
- This diagnostic trouble code (DTC) indicates that the upstream oxygen sensor for Bank 2, is producing a negative voltage (somewhere between 0 and -1 Volts [negative 1 V]).
- The normal voltages that the O2 sensor should produce are between 0.100 to 1 Volt DC and these are in the positive numbers range. So, if the sensor is producing a negative voltage value, there's something wrong.
- You'll be able to verify if the O2 sensor is really outputting such voltage numbers with your scan tool (and you'll see how in this article).
P0153: Upstream Heated Oxygen Sensor (HO2S11) Circuit Slow Response (Bank 2).
- This diagnostic trouble code (DTC) is letting you know that the upstream oxygen sensor for Bank 2 is switching between a Rich and Lean condition very slowly (lazily).
- This DTC usually indicates that the oxygen sensor (O2S21) is too old and ready to retire. With the help of this test article, you'll easily be able to confirm if this is the case.
Where To Buy The O2 Sensors And Save
You could run down to your neighborhood auto parts store and buy the oxygen sensors you need there, but you'll likely pay twice as much than online.
If you need/want to save some money, you can buy them here:
UpstreamO2S11 & O2S21
DownstreamO2S12 & O2S22
