O2 sensor bad, when I have auto zone hook up and test they do show o2 sensor bad, but the codes are saying sensor 3 and 4 are bad. it doesn't say "bank 1 sensor 2". how do I know what sensor 3 and 4 are ?? thanks

You are in Limp Mode. You need to Reset the codes and see if they come back. If they do, you need a good auto electrician with a pro grade scan tool computer to diagnose electronically.

https://www.google.com/search?q=auto+electrician+near+me

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How to Diagnose a P0135 -Heater
Performance Bank 1 Sensor 1 (GM 3.5L) January 31, 2012 Updated: October 29, 2014 Written by: Abraham Torres-Arredondo Article Id: 371

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If your check engine light is on and you have a diagnostic trouble code P0135 stored in the PCM's memory... then you've come to the right place to test and troubleshoot the upstream oxygen sensor.
A P0135 DTC says: HO2S Heater Performance Bank 1 Sensor 1... and this means that the PCM (Powertrain Control Module = Fuel Injection Computer) has detected a problem with the front oxygen sensor's heater element or a problem in the heater's circuit (wires).
In this tutorial, I'll show you how to check the oxygen (O2) sensor's heater element and the two circuits that feed it with power (10 to 12 Volts) and ground with a multimeter.
In case you're wondering, where the oxygen (O2) sensor that the code P0135 is accusing of being BAD is... this bad boy is located on the exhaust manifold and before the catalytic converter.
To help you navigate this article, here are its main points:

1. Symptoms of a BAD Oxygen Sensor Heater Element.
2. What Tools Do I Need to Test Code P0135?
3. What Does the Heater Inside the Oxygen Sensor Do?
4. Circuit Descriptions of the Downstream Oxygen Sensor.
5. Start Here.
6. TEST 1: Oxygen Sensor Bank 1 Sensor 1 Test.
7. TEST 2: Checking 12 Volts to O2 Heater.
8. TEST 3: Checking the O2 Heater's Ground Circuit.
9. TEST 4: Ohming the O2 Heater Element.
10. P0135 O2 Sensor Heater Test Summary.

Buying a Digital Multimeter for Automotive Diagnostic Testing (found at: easyautodiagnostics.com).

Scan Tool.

1. Don't have one?... check out my recommendation: Abe's Scan Tool Recommendation.

Wire Piercing Probe.

1. Although this tool is not an absolute must, if you do buy one, you'll realize just how easy it makes testing the voltages inside the wires.
2. If you need to see what this tool looks like, you can see it here:Wire Piercing Probe.

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Applies To:

Buick Vehicles:

• Rainier 4.2L
  • 2004, 2005

Chevrolet Vehicles:

• Colorado 3.5L
  • 2004, 2005
• Trailblazer
  • 2004, 2005

3.5L
How To Test for a Blown Head Gasket (GM 3.5L, 4.2L)
How to Test the MAF Sensor and Codes: P0100, P0101, P0102, P0103
How To Test for a Blown Head Gasket (GM 3.5L -FWD)
All Articles: 3.5L "A day without sunshine is like, you know, night"
Steve Martin
MORE TUTORIALS:

I wouldn't trust anything the Zone tells you. Most oxygen sensor codes are NOT caused by the oxygen sensor. Of coarse, a lot has to do with WHICH O2 sensor code you have. For example, codes P0130,P0131,P0132,P0133, P0134, P0135, P0137, P0138, P0140, P0141, P0171 and P0172, are all valid oxygen sensor/fuel trim codes for a 2003 Chevrolet Impala equipped with a 3.4L V-6 engine.
How you would go about troubleshooting the problem depends on which "oxygen sensor code" you have. Many times, the code can be fixed by simply repairing a leak in a vacuum hose. Quite often, these codes are caused by faulty mass airflow sensors. Then again, every once in a while, the problem is actually the oxygen sensor itself. However, if you go by the knowledge and experience in diagnostics that exists at the Zone, you will be changing an oxygen sensor EVERY time. Then when that does not fix the problem, you will be out the cost of the oxygen sensor, PLUS you will STILL have to diagnose the problem to fix it!

Many people think that all an automotive repair technician does is plug in the "magic box" and replace all the parts that the box (computer) tells them to replace (and the people at the Zone like it that way). TRUST ME, it does not work that way! I WISH it was that simple.

FYI: On Board Diagnostic (OBD) Diagnostic Test Codes (DTCs) NEVER tell you what parts to replace. They are called DTCs because for a trained technician, they tell him which of the hundreds of DIAGNOSTIC TEST ROUTINES to perform in order to diagnose the fault and pinpoint the CAUSE of the problem.

Just a little professional advice from someone who has been diagnosing and repairing cars for about 37 years...do with it as you will.

Hello: I don't know where you got that code from or what kind of scanner was used or if the operator of the scanner enter the truck information correctly. I think the code is po45 which would indicate the rear O2 sensor is faulty or faulty wiring to the rear O2 sensor. The rear O2 sensor is behind the catalytic converter. I would get the code re-checked again. Auto Zone O'REilly or Advance auto will normally check the code at no cost to you.

When you had one go bad, it fixed the problem for a short while. Now both they say are bad. 02 sensors last a long time if the engine has regular maintenance. Most likely your catalytic converter is bad. This will cause, at first the rear 02 to show bad readings setting a code. And as the converter progresses to get worse, it will make both 02 sensors give bad readings, thus setting off the codes.

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!

If was you o2 sensor the code would say o2 sensor bad. Your catalytic convertor may not be heating up enough to make the emission computer happy and is sending a trouble code.

P1336-crank or cam sensor
PO 141 & PO 171 are O2 Sensor Codes

All Auto Zone did, was confirm an issue with your
vehicle.
You don't know any more than when you went there

Find a good repair shop to diagnose your vehicles
problems.
You don't have all thoses parts failing and you replace
nothing without understanding the vehicles systems
and testing to determine if you even need parts to resolve

We could use a vehicle discription in the future

what code did they give the code will tell u something like "o2 lean bank ? sensor?" and if auto zone is telling u that its giving an o2 sensor problem most likely thats the trouble code that showed up and which sensor

One thing to check is the fuel pressure regulator.
If the diaphram is leaking it will cause gas to be pulled into the vacuum system causing lots of white smoke and extreme rough running.