PDA

View Full Version : Weird AFR Variance test in 0411 PCM 12212156 OS Datalog.



Fast355
09-05-2015, 05:02 AM
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.

http://i243.photobucket.com/albums/ff172/Fast355_album/AFR%20Test%201_zpsrtqatgnw.jpg



http://i243.photobucket.com/albums/ff172/Fast355_album/AFR%20Test%202_zpsvh1loskn.jpg

http://i243.photobucket.com/albums/ff172/Fast355_album/AFR%20Test%203_zpsnyvuasm1.jpg

mecanicman
09-05-2015, 06:02 AM
Rear 02s missing? Looks like the cat test.

Fast355
09-05-2015, 06:14 AM
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.

mecanicman
09-05-2015, 07:55 AM
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.

RobertISaar
09-05-2015, 07:20 PM
that pattern does sound like a cat/secondary O2 test.

Fast355
09-12-2015, 07:42 PM
Weird thing is, I have logged ALOT more data the past week and I have not seen a repeat of this test!