Hey Everyone! Question for you... I'm put in the programming for Short Term and Long Term fuel trims in my scangauge and have been looking at the readings. I've read up on Fuel Trim, the neg. and pos. numbers and such and I have no Engine Codes popping up.

I'm just wondering what numbers are others reading? I would like to see if I'm in the ballpark of others. I'm usually in the negitive numbers (less then -10%) for short term (and I'm assuming the SG reads it as a percent. I see -1 or -7... numbers like that)

What are you guys seeing??

Side note, I can't seem to get the programming for Air to Fuel Ratio to work on my '99. So I can't use that.

The fuel trim ratios represent the amount of fuel the PCM is adding or removing (in reference to a 'baseline') to keep the mixture at optimum based on feedback from the O2 sensors, temperature sensors, etc. When programming the PCM (like after changing injectors or MAF or intake tubing size) you disable 'learning' and adjust the mixture based on short term trim ratios, ideally getting them as close to 0 as possible. It takes special programming software to do that (you can't do it with the Scan Gauge).

As the vehicle runs the trim ratios will vary based on fuel mixture (winter/summer blends), temperatures, etc. Long term trim ratios vary less (thus they are 'long term'). Less than 10% variation is probably normal., especially for short term trims. It means your PCM is doing its job. If you are seeing 25% or more it probably means something is out of whack (dirty injector, bad O2 sensor or something). Since they are negative, it means the PCM is removing fuel (you're baseline is slightly rich). Again, that can be due to fuel mixture, temperatures (it is cold in Alaska this time of year), your K&N, etc.

Maybe this is common for everyone, but this monitoring is new to me (regarding fuel trim). It seems these numbers change with fuel ups and noting that in the scanguage. Up until yesterday my long term was reading in the -21 to -14 range. I fueled up last night, noted that in my SG, and my long term was sitting at 1 for the 15 miles to my house.

Bumping this really old thread to see if anyone can get there fuel trims to read with the current x gauge commands? I am trying to get mine to come up for my 99 Tacoma, but only the stft for banks 1&3 are working.

Im needing to view my long term trims to tune my AEM fic6.

Thanks,

Here's what is working on my '99 CA spec 4Runner:

Short term fuel trim:
TXD: 686AF10106
RFX: 044105060000
RXD: 2808
MTH: 00C80100FF9C
NAM: ST%

Long term fuel trim:
TXD: 686AF10107
RFX: 044105070000
RXD: 2808
MTH: 00C80100FF9C
NAM: LT%

Trans temp:
TXD: 686AF101B4
RXF: 044105B40000
RXD: 2808
MTH: 00090005FFD8
NAM: TFT

-Charlie

Thanks Phatty,

I think Ive tried that one, it is "LF1" from the scan gauge list, but Ill input it again to verify. I know your name of "LT%" is different from what I was inputting, maybe that has a bearing it?

It easy to get the numbers and letters wrong entering this long strings. Been there with the ScanGauge. I keep mine in my Saturn. Long term fuel trim is a great way to see the overall health of your fuel system and input sensors.


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The name section has no bearing on the results - put what makes sense to you there. Just re-check those numbers very carefully...

Good luck!

-Charlie

I must of had it typed incorrectly because your code is the same as LF1 in the link I posted and now it WORKS!

Anyway thanks for posting.

I am having issues with the p0403 and p0402 codes and my long term fuel trim bank 1 never changes even if i rev and hol dit. also short term fuel trim B1-S2 is stuck on 99.2% and doesn't change....any ideas?

Are you going closed loop?


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