GM Truck Club
THE PREMIER CHEVY TRUCK & SUV FORUM
Founded in 2004 ~ We're the #1 Chevy Truck & SUV Forum.
Silverado & Sierra | Tahoe & Yukon | Suburban & Yukon XL | SUV & CROSSOVER
Results 1 to 7 of 7
  1. #1

    Question Weird O2 sensor readings

    Recently I bought an OBDII Bluetooth adapter to monitor my Tahoe's engine performance and see extra/more exact info from the ECU. Currently my o2 sensors are giving conflicting readings.

    What do I mean? Well the pre cat sensors at idle were reading a F/T of -1.6% for both the 1x1 and 2x1 sensors. While the post cat sensors are reading a F/T of 99.1% for both 1x2 and 2x2 sensors. Based on the info I've learned these readings are impossible. Does any one have an idea whats up with these readings? I have been getting a p0340 cat three way inefficiency code for the pass side cat recently, but the code keeps going away even tho its a major code that should stay in the ECU for a long time.

    Pic from torque app at idle:
    Click image for larger version. 

Name:	Screenshot_2013-06-06-20-05-18.jpg 
Views:	81 
Size:	84.7 KB 
ID:	52885

    1996 Chevy Tahoe LT 5.7L V8 4X4 205,000+ miles. Built proudly at Janesville Assembly in Janesville, Wisconsin
    Basic mods: Lights all over, bunch of electrical work, and a couple cooling mods.

    Check out my other mods in My Garage: http://www.gmtruckclub.com/forum/sho...t-Tahoe-4-Door

  2. #2

    Default

    the P0430 code indicates that you have an air leak on the passenger side, or the cat is bad, or that passenger side rear O2 sensor is not connected to the wiring harness, or the wiring is bent, broken, melted, burned, etc...

    what is the F/T reading supposed to be of?? it's not fuel trims, because the fuel trims don't go that high...
    06MonteSS


    2014 Camaro SS - 2SS, RS pkg., short-throw shifter, NPP perf. exhaust, BMR strut-tower brace, Cold Air Inductions cold air intake

  3. Thanks Conlan Rose thanked for this post
  4. #3

    Default

    Is it possible that the reading from the rear sensors isn't actually fuel trim like the fronts and it wrong because they don't measure fuel they measure % of co2, co and o2.

    Also my p0430 code goes away on its own sometimes and only sporadically shows up. It makes trying to figure out what I need to fix very hard. Also the pass side used to have a weird sound for a while, which is now gone) I have a video of it I'll post and the pass side rear sensor is brand new (AC Delco)


    1996 Chevy Tahoe LT 5.7L V8 4X4 205,000+ miles. Built proudly at Janesville Assembly in Janesville, Wisconsin
    Basic mods: Lights all over, bunch of electrical work, and a couple cooling mods.

    Check out my other mods in My Garage: http://www.gmtruckclub.com/forum/sho...t-Tahoe-4-Door

  5. #4

    Default

    get a can of CRC Mass Airflow Sensor Cleaner from your auto parts store and spray clean your MAF sensor.... a dirty MAF sensor could be causing it as well....
    06MonteSS


    2014 Camaro SS - 2SS, RS pkg., short-throw shifter, NPP perf. exhaust, BMR strut-tower brace, Cold Air Inductions cold air intake

  6. Thanks Conlan Rose thanked for this post
  7. #5

    Default

    Quote Originally Posted by 06MonteSS53
    get a can of CRC Mass Airflow Sensor Cleaner from your auto parts store and spray clean your MAF sensor.... a dirty MAF sensor could be causing it as well....
    I'll do that this week and see if it helps. Also thanks for the help, a lot of people don't seem to know much about these things on their vehicles and I wish to learn to use each little thing to save gas on my big beast as well as help her last a very very long time.

    Screenshot from today:
    Click image for larger version. 

Name:	Screenshot_2013-06-10-06-48-40.jpg 
Views:	50 
Size:	77.2 KB 
ID:	52905

    - - - Updated - - -

    More pics
    Click image for larger version. 

Name:	Screenshot_2013-06-10-06-52-57.jpg 
Views:	42 
Size:	77.5 KB 
ID:	52907Click image for larger version. 

Name:	Screenshot_2013-06-10-06-47-51.jpg 
Views:	43 
Size:	77.5 KB 
ID:	52908
    Last edited by Conlan Rose; 06-10-2013 at 08:53 AM.

    1996 Chevy Tahoe LT 5.7L V8 4X4 205,000+ miles. Built proudly at Janesville Assembly in Janesville, Wisconsin
    Basic mods: Lights all over, bunch of electrical work, and a couple cooling mods.

    Check out my other mods in My Garage: http://www.gmtruckclub.com/forum/sho...t-Tahoe-4-Door

  8. #6

    Default

    plus, only the front O2 sensors are the ones used for determining the fuel trims... the rear O2 sensors are just used to determine if the cat converters are functioning properly....

    the fuel trim parameters you want to look at are called long term fuel trim bank 1 and long term fuel trim bank 2
    06MonteSS


    2014 Camaro SS - 2SS, RS pkg., short-throw shifter, NPP perf. exhaust, BMR strut-tower brace, Cold Air Inductions cold air intake

  9. #7

    Default

    Currently with the free version of torque I can only see the instant trims which seem to switch neg and positive often. What voltage should the rear sensors be at if operating properly?

    1996 Chevy Tahoe LT 5.7L V8 4X4 205,000+ miles. Built proudly at Janesville Assembly in Janesville, Wisconsin
    Basic mods: Lights all over, bunch of electrical work, and a couple cooling mods.

    Check out my other mods in My Garage: http://www.gmtruckclub.com/forum/sho...t-Tahoe-4-Door

Similar Threads

  1. 95 Yukon - Weird Coolant Temp Sensor (to ECM) Issue
    By italie in forum Chevy Tahoe Forum (GMC Yukon, Cadillac Escalade)
    Replies: 0
    Last Post: 05-11-2013, 07:59 PM
  2. What do these O2 sensor readings mean?
    By fulltimer in forum General Chevy & GM Tech Questions
    Replies: 2
    Last Post: 09-28-2011, 10:23 PM
  3. Compression readings....
    By bigbluesub in forum GM Powertrain
    Replies: 3
    Last Post: 09-02-2010, 10:59 PM
  4. rough idle/vacuum readings
    By dsfloyd in forum GM Powertrain
    Replies: 4
    Last Post: 08-30-2010, 03:51 PM
  5. question about tire size and speedometer readings
    By CMS in forum General Chevy & GM Tech Questions
    Replies: 2
    Last Post: 08-15-2010, 02:28 PM

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •