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).
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.
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:
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).
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 (HO2S11) Circuit Slow Response (Bank 2).
“A common mistake that people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools.”