Question about 2004 GMC Envoy

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O2 "Check Engine Light"

Got a PO134 code when check engine light came on indicating faultly bank one sensor one O2 sensor. (Have one on each bank pre cat and one post cat, total 3)

Replaced that sensor only (bank 1 sensor 1) and now I get PO134 & PO154 and truck runs very rough/rich at idle. (154 is no communication w/PCM)

Have tripple checked all connections and they seem to be good. Auto parts shops say "requires two" on the parts listing. Since I only replaced one could that have caused the lack of communication between the O2 sensors and the PCM and cased my issue not being resolved?

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  • ralfe396 Mar 13, 2009

    Alternator seems to be okay. Guage on dash reads 12V+ and confirmed output with multitester at alternator.

    Truck is running very rich and stumbling at idle. Is worse than before I replaced O2 1st sensor. Prior to replacement I only had one code (P0134). After I replaced B1 S1, I now get multiple codes.

  • ralfe396 Mar 14, 2009

    Did a code reset from my OBDII reader and light did go off for a bit. Drove aboyt 15 miles and it came back on. Engine was still sputtering badly at stop lights/idle.

    Reread codes and now get P0154 No activity Bank 2 Sensor 1; P1153 H0251 Insuficient Switches Bank 2 Sensor 1

    Still curious on whether or not these sensors (pre cat) MUST be installed in pairs? (as indicated in parts listings.) Wondering if the new sensor on B1S1 is not communicating with the original on B2S1.

  • ralfe396 Mar 21, 2009

    Well,thought we had it fixed. Replaced second O2 sensor (b2s1) and after a few days and about 75 miles got SES light again. This time trouble code comes back as "P0155 02 Sensor Heater Circuit Malfunction (Bank 2 Sensor 1)"

    Both Bank 1 Sensor 1 and Bank 2 Sensor 2 are now new. Vehicle now seems to be running fine - no more stumbling and acceleration seems back to normal.

  • ralfe396 Apr 08, 2009

    After cleaning the Mass Airflow Sensor and resetting trouble code, SES light stayed off for two days and approximately 100 miles+/-. Now I'm getting the P0155 again. To answer emmissionwiz, both sensors I have replaced are pre cat Bosch units of the same part number. They visably appear a bit different than the ones I pulled out, but all three of my aftermarket parts stores here, list the same part number as the replacement (did not check w/dealer). Currently don't have a way to check fuel pressure but will shortly.



    The temporary light correction happened when I changed the air cleaner earlier in this process as well. Leads me to believe there might be intake issues??



    Any other thoughts?

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The difinition the scanner is giving is incorrect, I have a GM OBD code book in front this is a direct copy:
P0154 - Heated Oxygen Sensor (HO2S) Circuit Insufficient Activity Bank 2 Sensor 1
P0134 - Heated Oxygen Sensor (HO2S) Circuit Insufficient Activity Bank 1 Sensor 1
1st of was the O2 you replaced the one before the Cat converter on the bank of cylinders opposite the bank that has #1 cylinder in it?, next question was this an O2 sensor a factory replacement part? that may be the problem, although all sensors perform the same function of producing a Small voltage when heated they are not wired the same, they also have a heater in them to decrease the time the engine goes into closed loop and the PCM (pwertrain control module) takes over and uses the O2 feedback to change air fuel mixture, I thin u may have a sensor that is not correct for your truck, also be aware that an O2 code does not mean the sensor is defective, it can mean that but many times it is caused by a rich run condition or a lean condition in the engine, this can be caused by other components. As a solution replace both the before cat sensors (up stream) with Factory OEM sensors, the price is very close and u know they are correct, if u still get a code after resting the system then you have another issue, not the sensors, hope you haven't damaged the control (PCM), I have done electronic engine control at a new car dealer for 20 years, I am a master tech in this field.One last note also clean the inside of the Mass Airflow Sensor and check the fuel pressure, it should be about 55-60 PSI at idle.

Posted on Mar 21, 2009

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Hi,
the latest code is due to the connection problems related to the O2 sensors.
Check for short or open/ high resistance in wiring harness/connectors.

Posted on Mar 21, 2009

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Yes any time you change the bank 1 sen 1 you need to replace the bank 1 sen 2, if not it wil cause the overload of exhust to the used senors..your car is almost 5 years old, do you have a aftermaket exhaust, or factory?

Posted on Mar 14, 2009

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Was this an original equipment part (AC DELCO) if not then there is you problem there seem to be a problem with the parts you put in there from the code you mentioned. HOWEVER I WOULD RECOMMEND THAT YOU REPLACE THESE SENSOR IN SETS for example bank 1 sensor 1&2. bank 2 sensor 1 &2. Good luck and thanks for using FIX YA

Posted on Mar 13, 2009

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Its best to replace all sensors that are bad or malfunctioning all at the same time. check the pcm for moisture or water.

Posted on Mar 13, 2009

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Good afternoon and welcome to fixya.

this problem is not a major problem to fix. i do need to ask you if you reset the computer after you changed the o2 sensor? if not unhook the battery for a couple of minutes and rehook, once you do start the vehicle the idle will go up and down and search for default idle setting, once you drive the vehicle for approx. 30 mile the computer will reset to that particular way of driving, so make sure you drive it like you normally would. see if that helps and takes care of your issue. let me know if this helps so we can get you fixya'd.





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Posted on Mar 13, 2009

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O2 sensor is not well assembled , the codes are sensor not detected:

PO134 )- - RH bank, pre catalyst sensor-

PO154 ) - LH bank, pre catalyst sensor

Posted on Mar 13, 2009

  • Ginko
    Ginko Mar 13, 2009

    Another possibilty is that you replaced the wronfg sensor.

    Bank 1 is the sensor on the right, if you replaced the wrong sensor now you will get error on both sides.

    To test the sensors you can read voltages. The O2 sensors voltage fluctuate between 0.1v at the low end (lean) and 0.9v at the high end (rich) during operation.

    If this or any other solution will result helpful, do not forget to accept the solution at the end, or you will end up rewarding that great genius that posted " check out the alternator in your car.
    " just to score few free coins.

    Thanks and goodbye.


  • Ginko
    Ginko Mar 13, 2009

    Now you get error on both sensor, ensure that you did not replace the good one.

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Check out the alternator in your car.

Posted on Mar 13, 2009

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Yes, sounds to me like you may have replaced the wrong sensor.
Replace the other sensor on that side and reset your system by disconnecting and reconnecting your battery.
That should solve your problem.

Posted on Mar 13, 2009

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