Results 1 to 12 of 12

Thread: O2 sensors/LTFT/STFT are jacked up

  1. 02-28-2018 #1
    cainsw
    cainsw is offline
    Tuner in Training
    Join Date
    Oct 2008
    Posts
    16

    O2 sensors/LTFT/STFT are jacked up

    Looking for ideas. According to my scan tool, it is showing my B1S1 O2 stuck at .423mv, B2S1 at .389mv and both LTFT and STFT at 0. Any suggestions what may be causing this? Maybe a bad ground? Popped fuse? I would think it would be really strange for both O2's to die at the same time. Also, correct me if I am wrong but if I understand the STFT correctly, shouldn't they be throwing fuel to it based off of the low O2's? I haven't really looked at anything on the car at this point but plan to do so tomorrow.
    Reply With Quote Reply With Quote
  2. 02-28-2018 #2
    5FDP
    5FDP is offline
    Tuning Addict 5FDP's Avatar
    Join Date
    May 2012
    Location
    Rogers, MN
    Posts
    13,608
    Fuel trims being stuck or staying in a certain spot normally means something is unplugged or wiring issues.

    Even in open loop fueling the o2 sensors will fluctuate up and down with the rpms somewhat.

    If the engine is running in open with STFT open loop fuel control turned off it will not change anything on it's own. Also if the STFT is disable with closed loop enabled it won't change fueling either.
    2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.

    If you don't post your tune and logs when you have questions you aren't helping yourself.
    Reply With Quote Reply With Quote
  3. 03-11-2018 #3
    cainsw
    cainsw is offline
    Tuner in Training
    Join Date
    Oct 2008
    Posts
    16
    I can go to vehicle controls and click ON to closed loop and my fuel trims start working. I think the pcm is not switching to closed loop.
    Reply With Quote Reply With Quote
  4. 03-11-2018 #4
    5FDP
    5FDP is offline
    Tuning Addict 5FDP's Avatar
    Join Date
    May 2012
    Location
    Rogers, MN
    Posts
    13,608
    Without the tune file and a log I can't see what the current settings are.
    2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.

    If you don't post your tune and logs when you have questions you aren't helping yourself.
    Reply With Quote Reply With Quote
  5. 03-12-2018 #5
    cainsw
    cainsw is offline
    Tuner in Training
    Join Date
    Oct 2008
    Posts
    16
    I really appreciate your help. I will get a log and the tune tomorrow. It is in my other laptop at the shop. It is a completely stock tune other than tuned off rear O2's, EGR and air pump disabled and gear ratio change.
    Reply With Quote Reply With Quote
  6. 03-12-2018 #6
    cainsw
    cainsw is offline
    Tuner in Training
    Join Date
    Oct 2008
    Posts
    16
    Here is the tune
    Attached Files Attached Files
    Reply With Quote Reply With Quote
  7. 03-12-2018 #7
    cainsw
    cainsw is offline
    Tuner in Training
    Join Date
    Oct 2008
    Posts
    16
    he is a part of a scan. Not sure what you are wanting to see scanned though
    Attached Files Attached Files
    Reply With Quote Reply With Quote
  8. 03-12-2018 #8
    5FDP
    5FDP is offline
    Tuning Addict 5FDP's Avatar
    Join Date
    May 2012
    Location
    Rogers, MN
    Posts
    13,608
    The log shows that the engine is still cold enough to be in open loop fuel control for most of the log.

    What does it do if you reach over 130-140 degree coolant temp?

    Do they start switching then and then does it drop into closed loop fueling?
    2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.

    If you don't post your tune and logs when you have questions you aren't helping yourself.
    Reply With Quote Reply With Quote
  9. 03-12-2018 #9
    cainsw
    cainsw is offline
    Tuner in Training
    Join Date
    Oct 2008
    Posts
    16
    I posted the wrong log file. I have one that is exactly the same but with the coolant temp at 192. So it should go into CL by then right? Even at that temp it still has no activity on the STFT or LTFT
    Reply With Quote Reply With Quote
  10. 03-12-2018 #10
    5FDP
    5FDP is offline
    Tuning Addict 5FDP's Avatar
    Join Date
    May 2012
    Location
    Rogers, MN
    Posts
    13,608
    Then it's wiring or sensor related if it won't enter closed loop and the o2 sensors are not moving.

    Nothing in the tune file itself looks to be stopping it from switching like normal or entering closed loop.
    2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.

    If you don't post your tune and logs when you have questions you aren't helping yourself.
    Reply With Quote Reply With Quote
  11. 03-13-2018 #11
    cobaltssoverbooster
    cobaltssoverbooster is offline
    Senior Tuner cobaltssoverbooster's Avatar
    Join Date
    Dec 2008
    Location
    Nevada
    Posts
    4,452
    Are you using the sae trim channels? I've logged one channel non sae and had no read of values before. Easy to try vcm channels and double check activity
    Reply With Quote Reply With Quote
  12. 03-16-2018 #12
    cainsw
    cainsw is offline
    Tuner in Training
    Join Date
    Oct 2008
    Posts
    16
    Just in case anyone else has having this same issue. I checked for vacuum leaks, checked the grounds, everything I could think of and couldn't find anything. I kept putting off replacing the O2's just for the fact that they took a dump at the same time. Since I couldn't find anything else I decided to just replace them. Well, that fixed it. Now it is just really really rich at idle even though my wideband is showing it to be dead on at 14.7. Gotta figure that out now
    Reply With Quote Reply With Quote
« Previous Thread | Next Thread »