Question about 2003 Chevrolet Silverado 1500

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O2 check engine light

I have a 2004 chevrolet 1500 Z71. I have a check engine light I am getting codes for the MAF sensor, the O2 Sensor it was the heating element code. I don't have the codes on hand. But any way I checked the MAF sensor all elements are intacked, cleaned it with some non residue electrical cleaner. I also removed the fwd and aft O2 sensor both were clean as could be. Cleaned them anyway with same cleaner. Checked out the vac lines to the intake, and intake manifold and started the truck and sprayed around intake manifold to check for leaks. The truck has high flow aftermarket cats that are 30,000 miles old so they aren't cloged. The truck runs fine, I haven't had any issues other than I had to put a new alternator on it today. I just cannot stand a check engine light. Any suggestions.

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  • bushman244 Jan 03, 2009

    What would be the best way to check the MAF without replacing it, Could I unplug it or something. What is the purpose of that screen in it also.

  • Anonymous Jan 10, 2009

    I have a 2003 chevy silverado and it is doing the same thing engine light came on said bank 1 bank 2 system to lean truck lost power would not go over about 25mph changed o2 sensor all four.. and the trucks engine is still running rough.. took it to the mech.. after about 1,000.00 changed mapp sensor mass air flow sensor changed coils spark plugs crack shaft postion sensor check the brain of the truck by changing it out with a new computer nothing need less to say 1,000.00 dollars and about 2 months later still have the same problem. now the engine light comes on and says random misfire.. i don't know what to do can anyone help

  • Anonymous Mar 22, 2014

    Engine engine is idling high after replacing stock exhaust manifolds and putting on headers

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U may indeed have a faulty MAF or O2 sensor, the way to tell if the MAF or a vacuum leak is at issue is that both O2's will code lean, if only one codes lean then it is most likely just a faulty O2 sensor, I don't have your codes but this is the way we do things at the dealer for problems like yours. Remember the O2's are before the Cat's., after the Cat's they are called Cat efficiency monitors in the book.

Posted on Jan 03, 2009

  • yadayada
    yadayada Jan 03, 2009

    I gave u the information u need to figure out the problem, follow my advice or not, that is up to u, the screen is a filter to keep leaves and debris out of the intake, u can't disconnect the MAF, it is the heart of the fuel system. If u unplug it the check engine will come on and the truck will run the same, U will need to check the signal return voltage to verify proper operation, you will need a scan tool with live data capabilities to do this function of testing, with this type of tool u can look at O2 signals as well, the service manual will give u the expected values at different loads and conditions. Please change my rating to helpful, I do this on my own time, just trying to help u out, I am not employed by Fixya, just use there site to get questions. Happy New Year. and good luck on a fix for this problem.

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I have a 1999 Silverado K1500 that started doing the same thing....the codes told me nothing...another wrench told me I needed a $900 head gasket repair, another told me I needed a $290 Injector replacement........what I had forgotten was that I ran a can of HEET through my tank..when that gas was gone so was the problem.

Hope this helps

Posted on Jan 03, 2009

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1997 Chevy 1500 z71 5.7 vortec I got P0102 P0441 P0340 codes on check engine on all the causes for each code it lists the PCM HAS FAILED HOW DO I CHECK to rule this out before I know I definitely have to...


It isn't the PCM. You most likely have a bad, dirty, or plugged mass air flow sensor. The cam position sensor is also a notorious failure, so that's a possibility. Most likely it is that the MAF sensor has caused an evaporative emissions systems error, and the engine timing is one of the things the PCM tries to adjust to meet compliance with the air/fuel/spark requirements to run cleanly. If it can't adjust the timing enough to correct it, then the cam position sensor will attempt to operate out of its limits, setting that code. Check your MAF sensor. Clean it or replace it, reset the codes, and drive it. If there is another problem, it will tell you.

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Apr 26, 2013 | 2004 Chrysler Sebring Sedan

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What is usally the problem when a po171 code


  • Hi, I can help.

  • Bank 1 O2 sensor has detected to much air.

  • First thing to try is cleaning the MAF sensor and see if this helps.
  • Check the PC valve and the connecting hose for cracks or being rotted.
  • Check for any vacuum leaks.
  • After this replacing the MAF sensor is recommended.
  • Sometimes the O2 sensor can cause this code too. The sensor will be on bank 1. If you pop the hood bank one is off the manifold on the right side of the engine as you look at the engine.

  • If you have any comments please feel free to leave them here.
  • Hope this helps and thank you for using FixYa.

Regards, Tony

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One of the o2 sensors are bad on my 2003 silverado z71 (5.3) and my truck just started missing really bad, almost to the point where I cannot drive it. Could the bad o2 sensor cause this or could this be...


Yes your o2 sensor could do this, it's most likely the closest one to the motor, the first one that is coming from the engine. That is the one that reads the exhaust gas, it then tells the computer how much gas to mix in with the air. It also could be your MAF(mass air flow sensor) connect to your intake.

*PS I have the same motor, wouldn't hurt, might get better MPG.

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If your O2 sensors are malfunctioning, the main symptom would be that the Check Engine light will come on. On some vehicles, an O2 sensor circuit shorted to ground can cause a no-start problem.
If the "Check Engine" or "Service Engine Soon" light is on and there is a code for the O2 sensors, I would like to also advise you that many O2 sensor codes are not caused by the O2 sensors themselves. In many cases, the O2 sensors are only REPORTING the problem. for example, a code P0171 "Oxygen Sensor Lean" code is rarely ever caused by the O2 sensor. It is usually caused by a vacuum leak or a failed Mass Airflow sensor (MAF) or Manifold Absolute Pressure sensor (MAP) or a bad fuel injector. In these cases, repairing the real reason that the engine is running lean will fix the O2 Sensor code without replacing the O2 sensor.

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The first time I had it scanned it said MAF malfunction, Then Codes 420& 430, saying bank1 &2 are bad. Then, I had those codes erased, and drove again to see when the check engine lite would come...


Hi, the o2 sensor codes may be a result of the maf. If the mass air flow sensor does not show the correct flow, the fuel mixture could be accomodating accordingly, resulting in a rich, or lean condition, setting codes. If there is a plugged, or restricted air filter, or a piece of debris on the sensor, this could cause a faulty reading. Also, make sure the air duct is tight at the throttle body, and the maf sensor is tight. Last, if you use a K&N filter, that uses an oil charge, there may be oil residue coating the maf sensor, causing an issue, or just a faulty sensor. At any result, I feel you should fix the maf issue, before the o2, as this is the order of operations, and you may not need o2 sensors. Good luck...Coop

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The check engine light has come on for our 2006 Chevy Silverado Z71. Checked battery connection. No other problems noticeable.


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3 Answers

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you have to know what the code is that your truck putting out your truck has 4 O2 sensors. the trucks computer is smart and the code will tell you witch one is bad but if you replace just one the next one on the same exhaust pipe will probley go bad so its safe to replace all four. the draw back to replaceing all of them is thay cost about 80 bucks for one ACDelco O2 sensor. It has to be done before it will pass Emissions. not a hard part to change about a 7/8 open end wrench will take it off. have fun.

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