Results 1 to 6 of 6

Thread: Weird AFR Variance test in 0411 PCM 12212156 OS Datalog.

  1. #1
    Fuel Injected!
    Join Date
    Feb 2013
    Location
    Euless, TX
    Posts
    2,305

    Weird AFR Variance test in 0411 PCM 12212156 OS Datalog.

    Just ran across this and notice it in a datalog for the first time. What is the PCM searching for??? Is it part of the catalyst efficiency testing or perhaps something with the 02 sensors and closed loop fuel control or perhaps both?? All I know is my cammed L31 doesn't like it much at all. I actually felt the shudder in the idle when this happened and thought it was an odd feeling event and searched for it in the datalog. The PCM leans out the mixture for 2 1/2 seconds, then bumps it richer for 2 1/2 seconds, then levels back off where it was to start with. The whole event was about 5 seconds overall. I noticed the test right after the engine had fully warmed up on the highway and I had exited the highway and was stopped at a traffic light. The test happened almost immediately after the engine returned to idle and the VSS registered zero.








  2. #2
    Fuel Injected!
    Join Date
    Jun 2013
    Posts
    199
    Rear 02s missing? Looks like the cat test.

  3. #3
    Fuel Injected!
    Join Date
    Feb 2013
    Location
    Euless, TX
    Posts
    2,305
    Quote Originally Posted by mecanicman View Post
    Rear 02s missing? Looks like the cat test.
    Nope they are in place, hooked up and turned on although the Catalyst Efficiency codes are set to No Error Reported. I have thunderbolt metallic core cats and the 02s are in spacers with a tiny hole drilled into the exhaust pipe. Never saw a code for a cat but I deleted the codes anyway.
    Last edited by Fast355; 09-05-2015 at 06:19 AM.

  4. #4
    Fuel Injected!
    Join Date
    Jun 2013
    Posts
    199
    Quote Originally Posted by Fast355 View Post
    Nope they are in place, hooked up and turned on although the Catalyst Efficiency codes are set to No Error Reported. I have thunderbolt metallic core cats and the 02s are in spacers with a tiny hole drilled into the exhaust pipe. Never saw a code for a cat but I deleted the codes anyway.
    Wonder if its because they are in the spacers, I have never used them.

  5. #5
    Super Moderator
    Join Date
    Mar 2011
    Location
    Camden, MI
    Age
    35
    Posts
    3,026
    that pattern does sound like a cat/secondary O2 test.
    1995 Chevrolet Monte Carlo LS 3100 + 4T60E


  6. #6
    Fuel Injected!
    Join Date
    Feb 2013
    Location
    Euless, TX
    Posts
    2,305
    Weird thing is, I have logged ALOT more data the past week and I have not seen a repeat of this test!

Similar Threads

  1. Replies: 8
    Last Post: 07-18-2022, 06:03 PM
  2. Disable cat test on 0411, anyone know how?
    By mecanicman in forum OBDII Tuning
    Replies: 3
    Last Post: 07-09-2015, 03:46 PM
  3. An other weird question... LT1 ECU on a TPI???
    By X-cabsquarebody in forum GM EFI Systems
    Replies: 13
    Last Post: 11-08-2014, 06:19 AM
  4. Weird O2 Sensor Reading on my Motor.... HELP?!
    By knuckle buster in forum GM EFI Systems
    Replies: 1
    Last Post: 01-11-2014, 04:11 PM
  5. Another Weird $42 .bin file ... what the heck $4A?
    By dave w in forum GM EFI Systems
    Replies: 4
    Last Post: 11-25-2012, 09:21 PM

Bookmarks

Posting Permissions

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