02 Sensor replacement

Tiny
MOWMIKE
  • MEMBER
  • 2004 FORD FOCUS
  • 2.3L
  • 4 CYL
  • FWD
  • AUTOMATIC
  • 203,000 MILES
My check engine light came on the code was P2274, I was told it was an oxygen Sensor that needed replacing so I bought one at Auto Zone and know I need to replace it (02 Sensor 3) but I am not sure where it is located could you tell me or give me an image of it please.
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Tuesday, June 23rd, 2015 AT 9:04 AM

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Tiny
WRENCHTECH
  • MECHANIC
  • 20,758 POSTS
Bank 1 Sensor 3 with be the furthest one back in the exhaust system. It will definitely be after the converter. Here is a guide to help you step by step with instructions in the diagrams below to show you how on your car.

https://www.2carpros.com/articles/how-to-replace-an-oxygen-sensor

Here is how to replace both o2 sensors. Check out the diagrams (Below). Please let us know if you need anything else to get the problem fixed.
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Tuesday, June 23rd, 2015 AT 9:42 AM
Tiny
TTHUL
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  • 2004 FORD FOCUS
  • 6 CYL
  • FWD
  • 90,000 MILES
What would be causing oil to get on the o2 sensor we have changed 2 out of the 3 sensors. A mechanic can't figure out why there is oil on the sensor so he just cleaned it off and now if will be about another 100 miles and then the light will come on and show the code for an o2 sensor. What would be causing the oil to go there.
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Monday, December 9th, 2019 AT 8:06 PM (Merged)
Tiny
WRENCHTECH
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You can't clean an 0/2 sensor.
Are you seeing this oil on the outside of the sensor or on the part inside of the exhaust?
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Monday, December 9th, 2019 AT 8:06 PM (Merged)
Tiny
TTHUL
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The mechanic took it out of the harness and he said that it was covered in oil.
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Monday, December 9th, 2019 AT 8:06 PM (Merged)
Tiny
WRENCHTECH
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That doesn't answer my question. If the oil is on the outside, that just means you have an oil leak and it isn't effecting the sensor. I don't see a possible way to get the inside wet with oil. If it did happen to get oil on the sensor itself, it would be junk after that.
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Monday, December 9th, 2019 AT 8:06 PM (Merged)
Tiny
KENMUL
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  • 1 POST
  • 2004 FORD FOCUS
2004 Ford Focus

How do I find and replace the O2 Sensor? An Auto parts store used the diagnostic device which indicated the O2 sensor needed replacing. Just need to know how.
Thanks
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Monday, December 9th, 2019 AT 8:06 PM (Merged)
Tiny
BLACKOP555
  • MECHANIC
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Well locate o2 sensor, remove harness and run the engine enough to heat up the o2 sensor and bung that way it comes out easier. Use a o2 sensor removing socket, they are very easy to use and are less likely to round out the o2 sensor, but a 6 point wrench works just as well.
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Monday, December 9th, 2019 AT 8:06 PM (Merged)
Tiny
TIMGOINCRAZY
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  • 3 POSTS
  • 2004 FORD FOCUS
Engine Performance problem
2004 Ford Focus 4 cyl Two Wheel Drive Automatic

After being prompted by a code I replaces sensor one bank one on my focus. The car no longer dies and runs fairly smooth with a little sputtering. The check engine light came back on and is now throwing code P0054. This website does not include this code but my parts store says
Repair resource for sensor location identification and refers to a failure in the the powertrain control module.
I have no idea where to go from here. Any help would be greatly appreciated.
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Monday, December 9th, 2019 AT 8:06 PM (Merged)
Tiny
BLACKOP555
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P0054 HO2S Heater Resistance (Bank 1, Sensor 2)

that sensor is for catalytic convertor efficiency. Doesnt affect fuel air ratio but if you want to fix it I would suggest checking the connector and wiring on that sensor to make sure its not shorted or open. If thats all good up to pcm check sensor
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Monday, December 9th, 2019 AT 8:06 PM (Merged)
Tiny
TIMGOINCRAZY
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Thanks for the advice and clarification.
Since I last posted my question I have changed the down stream O2 sensor and checked the wiring and all the plugs. Nothing seems damaged. All the shrouding is intact and none of the plugs are fouled or bent. The car is running just as bad as it was before I changed the upstream O2 sensor. I am at a loss. I am afraid the PCM I malfunctioning. Any more advice would be greatly appreciated.
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Monday, December 9th, 2019 AT 8:06 PM (Merged)
Tiny
BLACKOP555
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Are any new codes showing up on the vehicles computer or no. If so post back the exact codes. Try to unhook the exhaust piping from manifold. Run better now?

When does it run worst. Cold, warm? Al the time?

Acceleration good. Crusing good?
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Monday, December 9th, 2019 AT 8:06 PM (Merged)
Tiny
TIMGOINCRAZY
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I have been driving the car since my last post. The car does not seem to sputter at any specific time. It will sputter during acceleration cruising, idle and sometimes not at all. I did run the A/C for a bit and it died repeatedly. It is still sending the same code P0045. I have not yet unhooked the manifold. Should I drive it around with that unhooked?
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Monday, December 9th, 2019 AT 8:06 PM (Merged)
Tiny
J.DENNEY36
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  • 2003 FORD FOCUS
  • 4 CYL
  • FWD
  • MANUAL
  • 86,000 MILES
CHECK ENGINE light was on and went Auto Zone had it checked on dianostic and got code p0133 (heated oxygen sensor bank 1) Question, I need to know where this is located, can you help? My car is a 2003 SVT Ford Focus 4 cyl.
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Monday, December 9th, 2019 AT 8:06 PM (Merged)
Tiny
BLACKOP555
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Yeah try it and see if its better. Exhaust system could be plugged up causing vehicle to run poorly.

The vehicles having issues with o2's so check the cooling system. Have it pressure tested to see if coolant is leaking into the cylinders causing bad running and issues with the o2 sensors.
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Monday, December 9th, 2019 AT 8:06 PM (Merged)
Tiny
WRENCHTECH
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That sensor is right in the exhaust manifold at the front of the car. The heat shield will have to be removed to access it.

https://www.2carpros.com/images/external/86101635.gif
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Monday, December 9th, 2019 AT 8:06 PM (Merged)
Tiny
RANDY SHARP
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  • 2003 FORD FOCUS
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I have a 2003 Ford Focus zx3 2.3 Litre motor.I have been having a misfire code PO302 cylinder 2. It is a unusual problem because it cuts out when ac is turned on turn it off it is fine, but some times it will cut out without ac running. But I have a another DTC number, well we had Pep Boys scan it and it came up with P2274, and I think it suppose to be P127, 02 Sensor Signal Stuck Lean-Bank 1 Sensor 3.I understand the bank one front of motor, but where is Sensor 3 located. And does anybody out there know how to test them. Thanks
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Monday, December 9th, 2019 AT 8:06 PM (Merged)
Tiny
CARADIODOC
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One thing to consider with the type of symptoms you described is a bad diode in the generator. That will reduce its maximum current output to exactly one third of its rated value which is not enough to run the entire electrical system under all conditions. A professional load-test will show that. With one bad diode of the six, "ripple" voltage will also be very high.

As for testing an oxygen sensor, the Engine Computer does that for you. You can watch its signal on a scanner, and you can introduce rich and lean conditions to see if it responds, but you have to remember they only measure unburned oxygen, not unburned fuel.

Normally when three oxygen sensors are used, number three is the one after the catalytic converter.
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Monday, December 9th, 2019 AT 8:06 PM (Merged)
Tiny
RANDY SHARP
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So your saying the alternator could have a bad diode, but I just replaced the alternator about a year ago. And the 3rd 02 sensor is after the cat. Let me ask you a question my friend, you seem very knowledgeable, on mechanics.I want to purchase a 0BD 2 scanner, what kind would you recommend?And I surely appreciate all the help and advise you have given me.
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Monday, December 9th, 2019 AT 8:06 PM (Merged)
Tiny
CARADIODOC
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A bad diode is just one of the possible causes of what you described but it's an easy one to quickly rule out or find with a professional load-test. That involves drawing the maximum possible current for a couple of seconds to see what can be delivered, not a simple voltage test. Measuring battery voltage while the engine is running will tell if the generator is working but not if it is capable of delivering the full current it was designed to.

As for scanners, I have the Chrysler DRB3 because with an extra plug-in card it will do emissions testing on all brands of cars sold in the U.S. On '96 and new models up to at least 2004, and a few models beyond that. With another card it will work on all Chrysler products back to '83 models.

I also have the Chrysler DRB2 made for all Chryslers from '83 through '95 but it requires various plug-in cartridges specific to the line of models you're working on.

If money is no object, Snapon has the MODIS and a few other models but they get you with expensive updates every year. My coworkers used a Genysis and liked it a lot but I never used them so I don't know much about them other than they're a popular, less-expensive alternative to the Snapon stuff.

You also have to look at the cars you're going to be using this on. '95 and older models had all different computer systems. For those, other than Chrysler products, I have a Monitor 4000. One cartridge lets me work on GM, Ford, and Chrysler, but aftermarket scanners never do all the functions of the manufacturer's scanners. Starting with '96 models the manufacturers started trying to standardize their computer systems, at least as far as the computer language they used. All of those models have the "OBD2" emissions system, (on-board diagnostics version 2). Besides being able to get really specific with well over 1000 potential fault codes, that is when they added the oxygen sensors after the catalytic converters to monitor how well they're working. To my knowledge everything through the 2003 models uses the OBD2 system. You need a scanner that conforms to that language if you want to use it on this car.

Starting with a few 2004 models they switched to the current "CAN BUSS" system. That stands for "controller area network". Every switch and sensor becomes a small computer module, right down to the headlight switch and door switches. The chances of developing electrical problems skyrockets but supposedly the many on-board computers do much of the diagnosis for you. I've only worked on a few trucks so far and it has always been an expensive computer that has solved the problems. I DO know I will never own another new car after seeing how ridiculously complicated they're designing them now.

New scanners are real expensive but they become obsolete real fast too. You might look on some online auction sites for used ones. Larger repair shops have multiple scanners so no mechanic has to wait to use one, but when they start to see fewer older cars they will often sell most of that equipment and just keep one on hand in case one of those cars comes in. Don't waste your money on a simple code reader. Many auto parts stores will read codes for you for free. Full scanners display all the data the various computers are seeing from the sensors in real time. They also access all or most of the computers on the vehicles, not just the Engine Computer. They're "bidirectional" which means along with receiving and displaying data, you can talk to the computers and command them to do things like fire injectors and ignition coils, and turn the radiator fan on and off. Those things are real useful when diagnosing problems.

One thing you'll get with the Snapon MODIS, and possibly others, is troubleshooting tips that aren't included in manufacturer's scanners. It has a section that gives you the description of fault codes and things to check. The list of stuff to check is pretty basic for an experienced mechanic but it can be real helpful for guys like me when we aren't familiar with the car we're working on. Some tests get right down to telling you which wire color to test and what to expect to find. I always taught my students to figure out those test points on their own so they could do it when they didn't have a book or scanner to tell them what to do, but for people with no electrical training those test steps can often lead you to the cause of a problem and save you a trip to the mechanic. If you plan on keeping your car a while, $3000.00 for a used scanner can save you more than that in diagnostic costs at the repair shop.
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Monday, December 9th, 2019 AT 8:06 PM (Merged)
Tiny
RANDY SHARP
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Like I said before thank you so much for the information you have given me, I have been working on cars since I was 15 years old you know with dad, but I am not ase certified. Are you a teacher or something you are very knowledgeable about vehicles. Thank You for your time.
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Monday, December 9th, 2019 AT 8:06 PM (Merged)

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