Question about 1995 GMC Sierra C1500

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I have a 1995 sierra 5.7L and need to replace o2 sensor now the auto parts stores show i should have a 1 or3 wire harness but i have a 4 have you heard of this

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  • 51 Answers

Take them the old one

Posted on Oct 25, 2012


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Posted on Jan 02, 2017

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SOURCE: 02 sensors not ready

The code P0420 indicates that the catalytic converter is not functioning efficiently. This could be because the cat is damaged or the engine is not running very well and the cat cannot keep up with the emissions. You should ensure that the spark plugs and ignition components are in top shape before replacing anything else. If a compression check reveals a low cylinder, you will not be able to prevent this code as even a new cat cannot keep up with a dead miss. If the state of tune and the compression is good, then you'll likely need a cat.

I've posted the drive cycle just so you know what to do when you have resolved the code.

  1. Cold Start. In order to be classified as a cold start the engine coolant temperature must be below 122°F (50°C) and within 11°F (6°C) of the ambient air temperature at startup.
    Do not leave the key in prior to the cold start or the heated oxygen sensor diagnostic may not run.
  2. Idle. The engine must be run for two and a half minutes with the air conditioner on and rear defroster on. The more electrical load you can apply the better. This will test the O2 heater, Passive Air, Purge "No Flow", Misfire, and - if closed loop is achieved- Fuel Trim.
  3. Accelerate. Turn off the air conditioner and all the other loads and apply half throttle until 55mph (88km/hr) is reached. During this time the Misfire, Fuel Trim, and Purge Flow diagnostics will be performed.
  4. Hold Steady Speed. Hold a steady speed of 55mph (88km/hr) for 3 minutes. During this time the O2 response, air Intrusive, EGR, Purge, Misfire, and Fuel Trim diagnostics will be performed.
  5. Decelerate. Let off the accelerator pedal. Do not shift, touch the brake or clutch. It is important to let the vehicle coast along gradually slowing down to 20 mph (32km/hr). During this time the EGR, Purge and Fuel Trim diagnostics will be performed.
  6. Accelerate. Accelerate at 3/4 throttle until 55-60mph (88-96 km/hr). This will perform the same diagnostics as in step 3.
  7. Hold Steady Speed. Hold a steady speed of 55mph (88km/hr) for five minutes. During this time, in addition to the diagnostics performed in step 4, the catalyst monitor diagnostics will be performed. If the catalyst is marginal or the battery has been disconnected, it may take 5 complete driving cycles to determine the state of the catalyst.
  8. Decelerate. This will perform the same diagnostics as in step 5. Again, don't press the clutch or brakes or shift gears.

Posted on May 14, 2009

  • 9 Answers

SOURCE: 1999 GMC Sierra 5.3L knocking sound around Catalytic Conerters? ?

on my gmc i have 2 knock sensors and im not possitive if you have two or not under your intake mani but when i replaced both mine i got the same code of low input so i took the small needle out and wire brushed it clean and also traced and ran a new wire just to be safe and that solved my problem. as for bank 1,2 if it helps any my bank one is located engine side driverside and bank2 is engine side passenger side and 3 and 4 are underneath bed side. but you can see the sensors if you look real close near the headers. hope this helps
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Posted on Jul 02, 2009

  • 34 Answers

SOURCE: 7 wire harness going to blower motor resistor

There is an updated resistor/connector package. Very expensive from GM, try your local NAPA or other parts supplier for a replacement

Posted on Jul 09, 2009

  • 22 Answers

SOURCE: special wiring harness for new stereo in 2005 sierra

Yes u do....I have an 03 sierra and apparently they changed everything in 03.....the harness is over $100.....but u need it....and they dont sell a reg wiring kit from 03 and up....if it was an 02, then yes u could get away has to do with the steering wheel switches

Posted on Jan 24, 2010

  • 21 Answers

SOURCE: Engine light code 44 1994 GMC Sierra Pickup HD 5.7l, 4wd.

look for a serious exhaust or intake leak. look for bad wires to the o2 sensor or map sensor. just for starters.

Posted on Jul 20, 2010

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1 Answer

2004 jeep liberty P0139 code

PO139:O2 Sensor ckt Slow Response(Bank 1,sensor 2).This would be the odd side cylinders(1,3,5) and the 2nd oxygen sensor form the cylinder head.The sensor may be contaminated,or the heating element(on a 3 or 4 wire sensor) may not be working well.a good auto parts store should be able to show you a picture of where it is(the store will probably give you a printout if you buy the part form them!)

Sep 24, 2012 | 2004 Jeep Liberty

1 Answer

What does it mean when code P1133 comes up on your Grand Prix 2004 tes

Hi there:
DTC P1133 - Insufficient switching on Bank1 Sensor1 O2 sensor.

This is the O2 sensor located in the exhaust manifold. The vast majority of the time it is a faulty O2 sensor, but check O2 wiring harness for any chafing, as well as melting(resting on exhaust manifold):


To replace, disconnect the harness connector, and use O2 sensor socket to remove sensor. Once you change it, the code has to be cleared with a scanner. it wont reset itself. Most major parts stores will clear the codes for free. Make sure you get a direct fit O2 sensor. The universal ones that you have to splice into dont work right most of the time. They lose voltage in the wire splice and will reset the code.

Hope this helps; also keep in mind that your feedback is important and I`ll appreciate your time and consideration if you leave some testimonial comment about this answer.

Thank you for using FixYa, have a nice day.

Aug 21, 2012 | 2004 Pontiac Grand Prix

1 Answer

Has any one had problems with bosh oxagen sensor not working properly

Hi there:
Are you buy same or OE part replacement according with the Hyundai part number catalogue? This is important. Keep in midn that you need reset or delete all previous code stored in the car computer.

DTC P0131 - Oxygen O2 Sensor Circuit Low Voltage (Bank 1, Sensor 1)
Essentially the same as P0136 and P0137, a P0131 code refers to the first oxygen sensor on Bank 1. P0131 means the O2 oxygen sensor's voltage remained low for longer than 2 minutes. This, is interpreted by the ECM as a low voltage condition and sets the MIL. Bank 1 Sensor 1 is located in front of the catalytic converter.

There may be no visible symptoms to the driver, other than the MIL (Check Engine / Service Engine Soon) illumination.

A code P0131 may mean that one or more of the following has happened:
- Faulty o2 oxygen sensor
- Short to voltage on O2 signal circuit
- High resistance or open on O2 signal circuit

Possible Solutions:
- Replace faulty sensor
- Repair short, open, or high resistance on o2 signal circuit

Now, about DTC P0135 - Oxygen O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 1)

A code P0135 may mean that one or more of the following has happened:
- O2 Heater element resistance is high
- Internal short or open in the heater element
- O2 heater circuit wiring high resistance
- open or short to ground in the wiring harness

Possible Solutions
Repair short or open or high resistance in wiring harness or harness connectors
Replace oxygen sensor (cannot repair open or short that occurs internally to sensor)

Hope this helps; also keep in mind that your feedback is important and I`ll appreciate your time and consideration if you leave some testimonial comment about this answer.

Thank you for using FixYa, have a nice day.

Aug 17, 2012 | Cars & Trucks

2 Answers

How to replace oxygen sensor

At Autozone, Oreilly's, NAPA, etc, you will need to buy an O2 sensor socket. This looks like a normal socket but it's longer and has a slot running 3/4 of the way down one side. This slot is to hold your wiring harness to the side as you unscrew the O2 sensor.

First, be sure you're working on the right O2 sensor. Any auto parts store can diagnose this and get you the exact one. Many cars now have 2-4 or even more O2 sensors. Now, when they diagnose it they may say it's the front 'left bank' sensor or some other car lingo talk. Just let them point out to you which is the one causing your check engine light to come on so you know for sure. Also be sure you're buying the right O2 sensor wrench. I believe there are 3 or 4 sizes.

I dont do this, but most manuals would now tell you to disconnect your battery. Once its disconnected, find the O2 sensor in question and disengage the wiring harness. Just look it over until you see how it works, push down the plastic tab and it will pop right out. Now you'll have an O2 sensor sticking out of your exhaust with a wiring harness hanging on it. Use some PB Blaster to penetrate the threads and it will come out much easier. With O2 socket, remove. Replace. Reconnect harness. Reconnect battery. Fixya!

P.S. - I had a Ford Bronco that would constantly (every 3-6 months) show a check engine light and the RPMs would bounce back and forth when I started it. Turns out it was the O2 sensor. After replacing a few, an old mechanic told me to take it out and place the sensor end in acetone or gasoline for about 5 - 10 minutes. (not fully submerged, only the business end) Once you take it out, you can brush it off with a hard nylon or light metal brush, then repeat. Once the acetone has dried off, replace O2 sensor using steps above. Disconnect battery for a few minutes to clear the check engine code. Now, some say this doesn't work, but I can tell you from experience it definitely can. And, if the sensor is already showing bad, you could save $30-$120 depending on the cost of the O2 sensor.

Good luck!

Good luck!

May 01, 2011 | 2004 Buick LeSabre

2 Answers

Do i need special tools to replace 2001 Pontiac Aztek Oxygen Sensor

No special tools are needed, just use a open end wrench or adjustable wrench.

Dec 31, 2010 | 2001 Pontiac Aztek

1 Answer

P0155 o2 sensor problem

its harness is third from left and has a white wire,its a (heated) four wire sensor. by looking down at engine from top you should see these sensors. you can track the white wire and see that it is under car, a 22mm wrench, or a sensor socket will do good to take out. use blaster or wd40 to make the task easier to take out! if in doubt, call any auto parts store and they should be able to set ya straight.

Jul 26, 2010 | 2002 Nissan Sentra

3 Answers


You should have 5, O2 sensors on your Sirera. What are the DTC codes, each codes will indicate which O2 sensor needs to be addressed, or is this an answer with someone guess what the check engine light is saying.
Thye check engine light could be from a bad O2 sensor to just a bad or loose gas cap to a transmission issues.
Thank you for using fixya and note that Auto Zone and most larger auto parts store will scan DTC codes free of charge.

Jun 07, 2010 | 2006 GMC Sierra 1500 2WD

1 Answer

Trouble code po420 in my 2000 sierra

The O2 sensor after the Catalytic converter has gone bad or the converter it self. Lets start with the simple and replace the cheaper of the two but before you do that, check the wire harness where the O2 sensor clips on to the wire harness at the frame. Look for any damage to the clip such as corrosion or broken wire. Good luck and hope this helps.

Jul 03, 2009 | 2000 GMC Sierra

2 Answers

How do i install a o2 sensor myself?

The sensors that you purchased were probably universal. These are normally much cheaper than OEM replacement parts. They should have came with wiring instructions and extra parts, you will have to re-wire the harness. If you were not given the parts to change the plug then you may have been given the wrong sensors. You should call the Auto Parts store and double check the Part number to ensure that it is right. Also it could be that the vehicle does not have heated O2 sensors, if this is the case than you need to get O2 sensors that are not heated to replace them.

Jun 25, 2008 | 1989 Honda Prelude

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