what causes the fuel trims to stop responding?

[camcojb]

Doing some datalogging today and I noticed that sometimes while cruising down the road the trims go to "0" and quit responding. The a/f will start moving around a bit at this time since there's no O2 compensation. Then they'll go back after a bit. They might stay off for a minute or more, and it's not when the engine is cold or sitting idling. Are they somehow cooling off or is there something set in my tune incorrectly? I cannot find any correlation on my logs as to why they shut off, or why they go back on.

05 GTO LS2 with twin turbos.

Jody

[camcojb]

Is there a condition that is met, or a particular dtc that causes the trims to stop responding? I did set a P0430 catalyst efficiency yesterday, but I've seen the trims stop before without setting a code, all the while cruising down the road.

Jody

[EC_Tune]

Can you log the Fuel Trim Enable bit in the Status Bit section of the scanner? That should give you an idea why. Also log the O2 Sensor Enabled bits (if available).

[camcojb]

Can you log the Fuel Trim Enable bit in the Status Bit section of the scanner? That should give you an idea why. Also log the O2 Sensor Enabled bits (if available).

Will do.

Jody

[camcojb]

OK, did some logging. I can't tell what causes it to go off/on other than 40% tps kicks it off to open loop, but then it may or may not go back on when you let off. Sometimes it goes off/on/off/on in succession. I also could only find fuel trim learn, not fuel trim enable; I assume that's what you were talking about. There are no O2 sensor enable bits that I could see.

Here's the log if you want to look at it.

[Chris@HPTuners]

fuel trim learn disables on decel

[camcojb]

fuel trim learn disables on decel

I see that, but this does it cruising down the road, idling, etc. Fully warmed up too. I was just wondering if I may have something in the tune set wrong that makes it trip off randomly.

Jody

[Chris@HPTuners]

whenever you see fuel trim cell #38 that is decel for the LS2. If you see it during other fuel trims cells (apart from PE mode) then it could be your O2's.

Chris...

[camcojb]

whenever you see fuel trim cell #38 that is decel for the LS2. If you see it during other fuel trims cells (apart from PE mode) then it could be your O2's.

Chris...

OK, I see by looking at the datalog it goes off on #38. But I also see it shut off for cell #3, 20, 23 and I haven't looked at the whole log. In these cases the speed is steady and tps is also steady, yet it clicks off. So would that mean O2's? I can't imagine they're both bad on a brand new car.

Jody