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How to Replace an Oxygen Sensor Saturday Mechanic

By Amy Willis,2014-04-22 18:02
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How to Replace an Oxygen Sensor Saturday Mechanic

Unscrewing a sensor and replacing it is pretty straightforward. You might need this special socket to clear the wires.

By Ken Juran

    Photographs by James Westman

    Published in the August 2007 issue.

Twelve years and more than 100,000 miles have passed under your trusty commuter and the Check Engine light has

    never, ever, winked at you … until yesterday, when it coincidentally anticipated your state inspection appointment at the end of the month. Rats! The car will never pass the emissions test with that light on. Now what?

Here’s the perfect opportunity to break out that new, easy-to-use, consumer-grade OBD II (On-Board Diagnostics II)

    generic code reader. That’s what we did on our sacrificial lamb, a Nissan Altima. After plugging in the universal connector

    under the dash, we retrieved a code P0136 “O2 Sensor Circuit Malfunction (Sensor 2).” This let us zero in on the likely

    problem right away. Remember, a trouble code stored in the engine computer doesn’t necessarily tell you what’s wrong.

    It’s just a good starting point.

    So, it’s time to actually check out the sensor. Sensor 2 is the downstream sensor, in the catalytic converter, smack in the middle of the underside of the car. Start by getting the car up on some safety stands, then roll underneath it with a creeper.

Lazy O Sensor Equals Low MPG 2

    OBD I engine management, dating back to 1980, used just one upstream O2 sensor, mounted in the exhaust manifold, as

    close as possible to the cylinder head’s heat. That was because an oxygen sensor can’t produce and send the rapidly toggling voltage signal the engine computer is expecting until the sensor is really hot (above 600 F). That’s why today all

O2 sensors are electrically heated so they will start working sooner.

It’s always the upstream sensor (“Bank 1, Sensor 1”) that the powertrain management system pays attention to in order to

    fine-tune the proper 14.7:1 air/fuel ratio (aka lambda). Lambda is the Greek character used to designate that perfect

    stoichiometric ratio. And although the modern oxygen sensor has a 100,000-mile life expectancy, when it gets old and

    lazy you’ll begin to notice a drop in fuel economy. More extreme cases of malfunction will lead to driveability issues and,

    eventually, to an illuminated Check Engine light when the frequency of the sensor’s signal slows to a crawl.

Rules of Thumb

    It is possible to do some simple checks on O2 sensors with a high-impedance digital voltohmmeter. You don’t necessarily need a professional technician’s scan tool. But to perform specific test procedures, it definitely helps to have the service

    manual for your vehicle. Some manuals, for example, give simple static resistance measurements across the sensor’s

    terminals. These alone may not be conclusive.

Do a dynamic test. Determine the frequency at which a good sensor is supposed to toggle back and forth from 0 to 1 volt

    while the engine is being revved. A general rule of thumb says the sensor should toggle two to three times per second at

    2500 rpm. There are variations: Nissan says the rear heated oxygen sensor we replaced should read above 0.6 volt at

    least once while racing the engine up to 4000 rpm (under no load). Your service manual will have the specifics for your

    vehicle.

Or, you can just replace your O2 sensor(s) at regular intervals, to try and prevent that minor drop in mpg sometimes

    caused by a “lazy” high-mileage sensor.

Simple Replacement

    Our problem was obvious once we got under the car. The sensor’s harness had snagged on some road debris or, more

    likely, high-centered on a pile of ice here in New York last winter. With the harness dangling in the breeze, not connected

    to anything, it’s no wonder the Check Engine light was on.

But instead of just fixing the harness, we chose to go with a new $100 sensor. Its fresh electrical connector brought peace

    of mind. Besides, the old unit had been in service for 104,000 miles, so it was due for replacement. Despite the rust caked

    around the sensor’s mount, a good yank with an open-end wrench was all it took to break it loose.

    We got lucky, because this O2 sensor was easy to get at. More often than not, you’ll need to acquire one of the specially slotted oxygen sensor sockets, available wherever mechanic’s tools are sold. The slot in the side of these

    sockets enables easy removal and installation, even in cramped engine compartments, and protects the sensor’s wire

    leads.

Finally, after the sensor fix and a certain amount of driving and key cycling, we were waiting for the Altima’s Check Engine

    light to go out by itself. It didn’t. So we had to diagnose a little further. At last, we found two weak engine grounds. Their

    terminals had oxidized slightly on the aluminum intake manifold and were causing enough of a voltage drop in the ground

    side of the sensor circuit to keep the engine computer on guard. This caused two additional codes to store in the system

along with the O2 sensor code. Ultimately, loosening and retightening the two ground strap bolts allowed us to clear all the

    codes from memory. The Check Engine light blinked off and the car passed its emissions test with flying colors.

    1] Sometimes you get lucky: The old sensor unscrewed easily.

    2] A sparing dollop of antiseize will make the next removal easier. New sensors already have some on the threads.

3] Thread the new harness back into the body of the car. Make sure the grommet seals out road dirt and water. Use cable ties to keep

    the harness tucked out of the way.

    Reader Comments (502)

    502. 2000 Mitsubishi Galant Output Sensor

    I just replaced the output speed sensor on my car because the diagnostic code said it was malfunctioning. So, after 3 days

    the same code pops up again and again the speedometer is moving seriously crazy and all over the place. How does one

    fix this problem.

    501. RE: How to Replace an Oxygen Sensor: Saturday Mechanic How do i replace the O2 sensor on my s10 2001 chevy 3 door pick up , and how many sensor are there

    500. RE: How to Replace an Oxygen Sensor: Saturday Mechanic Where are the wire connections for the oxygen sensor on a 1992 Dodge Dakota 318 v-8 ?

    499. RE: Does Chev silverado 1995 has OxY sensor? I have changed the spurk plug wires, distributor cap, rotor and high voltage ignition coil to distributor but the engine is still

    running rough. I thought it may be due to Oxy sensor but I can't find it on the monafold or upstream the cat. convertor.

    Please help

    498. RE: How to Replace an Oxygen Sensor: Saturday Mechanic I can't find the O2 sensor on my '87 Olds with 3.8 L V6. Can you give me a clue where this sensor is RKRIP

497. RE: How to Replace an Oxygen Sensor 2005 HONDA ACCORD: Saturday Mechanic

    where is the sensor located on the 2005 accord , i can not see one from the top side of the manifold and do you need a

special socket to get it off .Thanks BOB

    496. RE: How to Replace an Oxygen Sensor: Saturday Mechanic 2005 Pontiac wave 5D, Where is the front O2 Sensor Heater Circuit? code p0135

    495. RE: How to Replace an Oxygen Sensor: Saturday Mechanic How do I change the O2 sensor on the passenger side exhaust on a 1996 mustang GT 4.6 L engine.

    494. RE: How to Replace an Oxygen Sensor: Saturday Mechanic How to replace O2 sensor bank 1 on a 2003 Chevy Avalance 1500 and the location.

    493. RE: How to Replace an Oxygen Sensor: Saturday Mechanic How do I replace O2 Sensor on 2001 Honda Accord?

    492. RE: How to Replace an Oxygen Sensor: Saturday Mechanic How many O2 sensors are there on my 2002 Dodge Grand Caravan, where are they located, and how do I replace them?

    491. RE: How to Replace an Oxygen Sensor: Saturday Mechanic I have a Benz SLK 230 yera 2000 and have "engine LT" on code is 730 Please help Thank you in advance

    490. RE: How to Replace an Oxygen Sensor: Saturday Mechanic I have a Check Engine light on, on a 2002 Saturn L300 sedan. Gas mileage is bad and the exhaust smells sulfer like. I

    suspect a bad oxygen sensor. Can you tell me how to replace it, and if I will need any special tools? Thanks a lot!

    489. RE: How to Replace an Oxygen Sensor: Saturday Mechanic my dodge dakota 2003 , coded p0138 high voltage 02 sensor , after the cat, so is this telling me i should just replace both

    02 sensors ?

    488. RE: How to Replace an Oxygen Sensor: Saturday Mechanic where do i find the sensor that would kick on my fans i checked the fans they work and the relays are good

    487. RE: How to Replace an Oxygen Sensor: Saturday Mechanic How to replace the o2 on a 2001 chevy silverado with code PO161 bank2 sensor 2

    486. RE: How to Replace an Oxygen Sensor: Saturday Mechanic How do you replace a O2 sensor on a hyndia elantra? And where could I find the O2 sensor?

    485. RE: How to Replace an Oxygen Sensor: Saturday Mechanic my engine light came on and i disconnected the battery to reset the engine light and it worked for a short period of time

    now it is back on ,and i only have 42000 miles on my 2004 ford f150 heritage. so what do you think the real problem is?

    484. RE: How to Replace an Oxygen Sensor: Saturday Mechanic how to replace an O2 sensor in a 97 pontiac sunfire... where is it located?

    483. RE: How to Replace an Oxygen Sensor: Saturday Mechanic p0161 code heater circuit bank 2 sensor 2.where is it located and how do i check it.1998 GMCtruck 5.7 litre

    482. RE: How to Replace an Oxygen Sensor: Saturday Mechanic What type or size screw or plug can I use to eliminate the sebsor on my 1987 Gran Fury. The original carb and electronic

    fuel control system has been eliminated

    481. RE: How to Replace an Oxygen Sensor: Saturday Mechanic 1990 jeep cherokee ltd. 4.0 liter: procedure to replace oxy. sen. Any special tools?

    480. RE: How to Replace an Oxygen Sensor: Saturday Mechanic 123. RE: How to Replace an Oxygen Sensor: Saturday Mechanic I have mitsubishi endeavour 2004 And I need to find out

    where is my o2 sensor bank 1 sensor 1 and sensor 2. and how to replace. thank you

    479. RE: How to Replace an Oxygen Sensor: Saturday Mechanic how do i replace a bank 1 sensor 2 on a 96 chevy cavalier . where is it located

    478. RE: How to Replace an Oxygen Sensor: Saturday Mechanic How to replace oxygen sensor at bank 1 sensor 2 of Mitsubishi endevour?

    477. RE: How to Replace an Oxygen Sensor: Saturday Mechanic How to replace oxygen sensor at bank 1 sensor 2 of Mitsubishi endevour?

    476. RE: How to Replace an Oxygen Sensor: Saturday Mechanic How do I change the oxengen sensor on a 1997 Accord LX. The sensor number code is p 0420 catalitis efishency.

    475. RE: How to Replace an Oxygen Sensor: Saturday Mechanic Where would i find the O2 sensor bank 2 on a 1995 Crysler cirrus?

    474. RE: How to Replace an Oxygen Sensor: Saturday Mechanic Where is the 2nd oxygen sensor located on 2002 Toyota Corolla? I had the Catalytic Converter changed and the check

    engine light went off but now two months later it is on again. Thanks for your help.

    473. RE: How to Replace an Oxygen Sensor: Saturday Mechanic My son was charged $550.00 to replace an O2 sensor in his 2001 dodge stratus. It seems like and easy job.

472. RE: How to Replace a 2001 Mercedes Benz S 500 Oxygen Sensor: Saturday Mechanic

    2001 Benz S 500 'Check Engine' light has been traced to needing a new (pre-catalic Con.) Oxygen sensor. Where is it and

    how do I replace it. Is there any other thing I need to consider when replacing this part?

    471. RE: How to Replace an Oxygen Sensor: Saturday Mechanic Where is the bank 1 sensor 2 on a 1997 Pontaic Gramd Am 4cyl

    470. RE: How to Replace an Oxygen Sensor: Saturday Mechanic

03 Nissan Sentra. Replaced both O2 Sensors Bank 1 Sensor 1 and 2. Check engine light will not stay off. With out me

    resetting it with code reader. P0037. Replaced Sensor 2 twice. Need help please.

    469. RE: How to Replace an Oxygen Sensor: Saturday Mechanic where is bank 1 sensor 1 on 1996 toyota 4runner 4wd?

    468. RE: How to Replace an Oxygen Sensor: Saturday Mechanic how to replace oxygen sensor in 2002 Jetta 2.0, 4 cyl.

467. RE: I have replaced O2 Sensor, Bank 1 Sensor 1 and the Catolitic converter, but the check engine light still

    says O2

    We have replaced the O2, bank 1 sensor 1 and catilitic converter, but the check engine light still says o2, bank 1 s.1

    466. RE: How to Replace a speed sensor 1995 3.8 alumina excellent directions for oxygen sensor but I need them or speed sensor

    465. RE: How to Replace an Oxygen Sensor: Saturday Mechanic location o2 sensor 99 dodge5.7

    464. RE: How to Replace an Oxygen Sensor: Saturday Mechanic where are the 02 sensors located on a 1990 mercedes 300E

    463. RE: How to locate an Oxygen Sensor on a 1997 Ford Explorer. I want to make sure I replace the correct O2 sensor. Need location of senor 1, bank 1, on a 1997 Ford Explorer XLT, all

    wheel drive, V8 engine automatice.

    462. RE: How to Replace an Oxygen Sensor: Saturday Mechanic I have got a 2005 dodge grand caravan sxt-check engine light came on , had read at autozone-bank 1 sensor bad. need

    to know where its at , and how to replace.really appreciate the help - thanks -chris -

    461. RE: How to Replace an Oxygen Sensor: Saturday Mechanic where are the o2 sensors, are they accesible. on a 2000 olds sillouette

    460. RE: How to Replace an Oxygen Sensor: Saturday Mechanic Can you provide instructions, diagrams, or pictures on replacing the oxygen sensors on a 1992 Ford F-150 2WD 5.0L

    engine

    459. RE: How to Replace an Oxygen Sensor: Saturday Mechanic how to replace oxygen sensors 1996 toyota corolla p0130 and p0133

    458. RE: How to Replace an Oxygen Sensor: Saturday Mechanic I need help with my 2000 Mazda protégé 1.8l ...I need to replace the upper O2 sensor (the one coming off the manifold)

    BUT my mechanic tells me that the old sensor is impossible to remove and that it seems to have melted into the manifold

    or something like that. Does this make sense or is he just trying to get me to pay for a new exhaust manifold AND a 02

sensor? If he is right is there anything I can do to get the old sensor out without replacing the entire manifold because that

    really isn’t something I want to do. Thanks a lot!

    457. RE: How to Replace an Oxygen Sensor: Saturday Mechanic how do i replace a air fuel ratio sensor on a 2000 honda civic lx?

    456. RE: How to Replace an Oxygen Sensor: Saturday Mechanic 2004 Chevrolet Aveo Wheres the O2 Sensor Heater Circuit? (Says Malfunction).

    455. RE: How to Replace an Oxygen Sensor: Saturday Mechanic How to Replace an Oxygen Sensor:For A Ford Expedition V8 5.4

    454. RE: How to Replace an Oxygen Sensor: Saturday Mechanic how do i replace O2 sensor circuit no activity detected, code is po134 and where is it located at?

    453. RE: How to Replace an Oxygen Sensor: Saturday Mechanic code P0135 02 sensor bank 1 sensor 1 came up where is that sensor on a 1998 ford contour gl? Thanks

    452. RE: How to Replace an Oxygen Sensor: Saturday Mechanic replace oxyygn sensor on 2005 jeep liberty

    451. RE: How to Replace an Oxygen Sensor: Saturday Mechanic need help! bank 1 sensor 2 is bad on a 2002 Isuzu Rodeo. Could you please tell me exactly where it is and step by step

    how to replace it. thank you

    450. RE: How to Replace an Oxygen Sensor: Saturday Mechanic 1995 ford mustang has a code of dlc # P1131 is the oxygen sensor bad and need to be replace? the rpm stayed 2500 0n

    idle tried to adjust the screw for idle but the RPM stayed the same 2500.where can i find your answer? please help.

    449. RE: How to Replace an Oxygen Sensor: Saturday Mechanic Where is the oxygen sensor in 1995 ford mustang located. I have a dlc code # 1131 and it say fuel is to lean. RPM is 2500

    at idle. Replaced the idler controller once but no change on RPM stay on 2500 to high for idle. Thank you for your help

    448. RE: How to Replace an Oxygen Sensor: Saturday Mechanic what should a oxygen sensor cost and how do i change it on my 2003 gmc yukon thanks

    447. RE: How to Replace an Oxygen Sensor: Saturday Mechanic My engine light is on and the mechanic says that according to the computer reading, it's the Bank II and Sensor II. Later, I

    found out that it was the oxygen sensor. I want to save labor costs and replace it myself. Can you please send me

    instructions for a Jeep Grand Cherokee Overland 2003? Thank you

    446. RE: How to Replace an Oxygen Sensor: Saturday Mechanic I was just told that 2 oxygen sensors need to be replaced on my 2002 Buick Rendezvous...it has about 88,000 miles...the

    mechanic told me that some other related parts have to be cleaned out....1 hour of labor and the cost is $700 + tax...I paid

for the diagnostic a while back so that's not in this cost...I did fail the emmissions test the other day and that's what that

    mechanic told me was the problem and why the engine light was on...I live in Stratford, CT...is this a fair rate as I was told

    would be around $2-300...but not $700...looking forward to your reply...thanx, Leon L.

    445. Replace an Oxygen Sensor: Saturday Mechanic 2000 hyun elantra need to know how to hard wire a universal 02 sensor after the cat. has 4 wire going to the harness-

    color code needed

    444. RE: How to Replace an Oxygen Sensor: Saturday Mechanic dlc #1131 ford mustang 1995 is the oxygen sensor bad? where is the sensor located. thank you

    443. RE: How to Replace an Oxygen Sensor: Saturday Mechanic DLC #1131 ON FORD. DO I NEED TO REPLACE THE OXYGEN SENSOR. DURING START THE RPM IS 2500 AT IDLE

    AND THE BUTTERFLY IS CLOSE WHEN YOU OPEN THE INTAKE HOSE.

    442. RE: How to Replace an Oxygen Sensor: Saturday Mechanic I need to replace the downstream Oxygen sensor on my 95 Blazer. Is this difficult?

    441. RE: How to Replace an Oxygen Sensor: Saturday Mechanic how do I replace oxygen sensor on 1999 lexus ES300? THANKS

    440. RE: How to Replace an Oxygen Sensor: Saturday Mechanic where is the oxygen sensor on my 2000 chevy silverado...any help greatly appreciated..thanx..

    439. RE: How to Replace an Oxygen Sensor: Saturday Mechanic I have a Dodge Grand Caravan 2001- 3.3 v-6 just had the engine replace now the check engine light is on diagnosed with

    bad upstream o2 sensor i believe it should be near the fire wall on the exhaust manifold, can you help me out??

    438. RE: How to Replace an Oxygen Sensor: Saturday Mechanic What cause the O2 sensor circuit to response slow? What cause the O2 system too lean and how can I fix it?

    437. RE: How to Replace an Oxygen Sensor: Saturday Mechanic How do I replace an o2 sensor in a 1992 buick lesabre custom? never done it before... please reply via email

    436. RE: How to Replace an Oxygen Sensor: Saturday Mechanic need to know how many O2 sensors are on 1997 4.6L and the location of sensors

    435. RE: How to Replace an Oxygen Sensor: Saturday Mechanic I have a 1997 Chrysler Sebring and need to know the location of the o2 sensor and step by step instructions on how to

    replace it .

    434. RE: How to Replace an Oxygen Sensor: Saturday Mechanic need to know where and how to change a oxygen sensor low circut voltage bank 1 sensor 2 on a 2002 chev malibu 3.1

    litre .thank you!

    433. RE: How to Replace an Oxygen Sensor: Saturday Mechanic I need to know where the downstream O2 sensor is and how to replace it on a 2002 toyota tacoma sr5 double cab 4 wheel

    drive truck. Thank you

    432. RE: How to Replace an Oxygen Sensor: Saturday Mechanic How do I replace a sensor in a 2003 chevy venture? I think it is #2sensor.

    431. RE: How to Replace an Oxygen Sensor: Saturday Mechanic where are oxygen sensors located on 99 ford windstar 3.8

    430. RE: How to Replace an Oxygen Sensor: Saturday Mechanic my check engine came on told it was my gas cap now my car just turns off while driving found i had a vachumeleak fixed it

    still turning off while driving is it oxygen sensor?

    429. RE: How to Replace an Oxygen Sensor: Saturday Mechanic I need help. bank 1 sensor 2 is bad on 04 dodge,stratus where is it located and step by step how to replace. Thank You

    428. RE: How to Replace an Oxygen Sensor: Saturday Mechanic i was told i need p0037,ho2's oxygen sensor bank #1 and#2 is the p0037 the ho2 oxygen sensor and is bank 1 and 2 two

    different sensors i need to purphase, and where do they exactly go on the vechicle. 1999 chevy blazer 4.3L

    427. RE: How to Replace an Oxygen Sensor: Saturday Mechanic How to replace o2 sensor on 1986 Honda Accord?

    426. RE: How to Replace an Oxygen Sensors: 1999'Chevy Tahoe 5.7L Website: Saturday Mechanic

    How many sensors are there and how do I know which ones require replacement?

    425. RE: How to Replace an Oxygen Sensor: Saturday Mechanic i have a 2003 isuzu rodeo and i need to know how to replace the o2 sensors

    424. RE: How to Replace an Oxygen Sensor: Saturday Mechanic How do I change the O2 sensor on my 2004 F-150 Heritage 6 Cyl

    423. RE: How to Replace an Oxygen Sensor: Saturday Mechanic location of o2 sensor / sensor 1 bank 1 on a 2005 chevy suburban 5.3l flex fuel

    422. RE: How to Replace an Oxygen Sensor: Saturday Mechanic I have a Ford Windstar 2002 with the engine light on. I have heard that a faulty head gasket allowing antifreeze to enter

    the combustion chamber can clog O2 sensors and cause a fault. Any comments?

    421. RE: How to Replace an Oxygen Sensor: Saturday Mechanic how do u change the sensor/where is it located on a 1997 Eagle Vision TSI

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