Question about 2005 Chevrolet TrailBlazer

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My o2 sensor has gone, but i do not know where it is to replace it. Please help!

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The O2 sensors located beside the cat converter.The one is pre-cat converter and other is pro-cat converter.The 1 before the catalytic converter and 1 after it. The 1 before is called the upstream and the 1 after is the downstream. ----------- Thanks.Helpmech.

Posted on Nov 12, 2010

  • Ryan Lutton
    Ryan Lutton Nov 17, 2010

    Lets hope the one upstream is the problem. That one is simple, right in the open, and takes about 15 minutes to do. The one down stream how ever is difficult, well at least the electricle connection is difficult. The connection is located on top of the transmission, talk about PIA!

  • raj somaiya Nov 18, 2010

    Yes hope for the best,but in most of the cases both the o2 sensors get faulty.Its not necessary but in most of the cases both o2 sensors has to be replaced.But you can go with replacement of upstream sensor first and check if still the problem is noticed.



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2006 Dodge Caravan Getting Two codes: Po135 and Po141

Sadly people don't know that trouble codes only tell the mechanic what to test, not what to replace. And auto parts stores are in the business of selling parts, not giving advice.
Code 135 means there is a problem with the heater inside the o2 sensor for bank one in front of the catalytic converter. Code 141 means the same thing for the o2 sensor after the cat.
Since it is very rare to have two O2 sensors fail at the same time, chances are the problem is lack of power going to the sensors.
The power circuits would need to be checked which requires a shop manual to get the testing procedures and wiring diagrams.

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Did you reset the codes after replacing the O2 sensor? It is possible sometimes that the values stored in the ECU for the earlier sensor may be giving the wrong readings. Try resetting the codes and see if it helps. Also, make sure that you replaced the part that was actually needed. If the OBD gives other codes, the problem might not be with the sensor.

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I need to know what tools to use when replacing oxygen sensor. and where on the car is the oxygen sensor located. Please help

22mm wrench or 15/16" or an O2 Socket

Which Sensor ?

#1 is closest to the engine,before or in the exhaust converter

#2 is the Monitor,in the converter outlet

O2 Sensors get replaced at 100,000 miles or
when they fail

Failing means you have to component test it,
to see if it works correctly.

80% of O2 Codes are Vacuum Leaks or Misfires

Jul 17, 2011 | 2000 Ford Contour

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Where are the o2 sensors located on 2004 dodge durango and how many are there?

I believe you may have three (3) O2 sensor, (2) of the sensor is on ether side of the exhaust down pipe and some times called up stream O2 sensor, the third O2 sensor know to some as the down stream O2 and is after the Catalytic converter.
The up stream O2 monitors the left and right side banks and sends signals to the ECM to make the adjustments to the injectors to keep the proper air/fuel ratio.
The down stream O2 monitors the catalytic converter and sends signal to the ECM if the catalytic converter has gone bad.
Good luck and hope this helps. If you get it scanned at Auto Zone, they should be able to let you know which O2 has gone bad so as to not change all three. You could always check the wire harness to the down stream O2 for corrosion.

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The wiring at the O2 sensor melted the O2 sensor plug in to .. i need to no the the color of the matched wire from the harness to the O2 sensor since the plug is gone , on the front passenger O2 to the...

There should be 2 ways of doing this. Get a portion of the wiring harness off a wreck or see if Ford can get you a new wire. Someone else may know more about this but some wires have heating elements in them and some may have resistance in the wiring. A plain wire would not be the same.

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How do you check the O2 sensor

hi, the only way to really check the o2 sensor is buy removing it then running power through it but this can damage it further.
The most common thing you will notice if the lambda sensor (oxygen sensor) when the car starts from cold and if it runs ok when you run the car upto temperature if when its hot the engine doesnt run correc then this is usually proof the o2 sensor needs replacing.

What makes you think the o2 sensor is gone and are you going on about the lambda sensor in the exhaust if not then im sorry but let me know then i can assist you further ok

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I need to know what the definition for fault code

The #2 O2 sensor on the cataylitic convertor,could be caused by a bad sensor or bad convertor.

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Location of oxygen sensor

Under the truck, driver side exhaust pipe, there are 2, 1 is before the catalytic converter, the other is after. They screw into the side of the exhaust pipe.

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