3rd Gen Scangauge II Owners!

[phattyduck]

Just watch Long term (and short term) fuel trims, depending on tire size and load/weight of vehicle, engine conditions ect,. you want to see the LTFT level out at or near +14 cruising around for any period of time at or around 70mph, if your seeing 19LTFT lean something is not right it's trying to richen the mixture up under load or certain conditions, 8LTFT rich cruising and it is trying to lean out the FT, like when you come off throttle, WOT or at idle which would be a LTFT normal condition During those conditions. This may take a few hours of driving for the ECU to learn/smooth out the LTFT for the best fuel economy under the conditions it is use to, every vehicle will vary a little and the conditions the vehicle is used in can effect the LTFT as well. You don't want the trans temp over 200-210 for any length of time really, hills are the killer where I live.

AHHHH!!! Fuel trims should all be near 0. (less than +/-5, max is +/-20)) It is not based on the 14.7:1 AFR for stoichiometric burning of gasoline - it is based on deviation from expected fuel needs for a given rpm/load.

-Charlie

 

[Malcolm99]

^yes exactly, 0%, that would be the "combined" FT that the ecu is going for your referring too under given rpm/load, the SGII just gives us LTFT and STFT% not combined or a AF ratio as you mentioned. 14% LTFT cruising at 70mph seems to be normal for a lifted 5vz-Fe on 32-33" tires and gear(12-16% LTFT seems common under that rpm/load on SgII) Yes WOT or off throttle it should be close to +\- 4-0% or working towards it.

 

[19963.4lsr5]

LTFT.STFT is the fuel trim.

The short term fuel trim is what the engine operates on in the here and now. If the short term maxes out at either -30 or +30 it will subtract or add a 1 to the LTFT and rezero itself and start over.

If you are driving around with a 14 in your LTFT you are close to getting the too lean code.

I’m anywhere from -3 to 8 on the LTFT. The lighter the load the higher my LTFT goes.


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[Malcolm99]

drove it for awhile maxing out at 19% LTFT as that is as much adjustment as it can do, it doesn't adjust or read higher than 19% for each FT parameter, never saw a code or pending code, it would have to max out both LTFT 19% and STFT each to throw the lean code or some thing like 30% Combined FT, my engine has 195PSI compression, replaced TPS as it wasn't reading 10-20% at all times, now I'm at 14% again cruising under load at 70mph, truck is working as it should. this is normal conditions for the LTFT. Try reading your LTFT and SHFT while driving it at 70mph.

 

[phattyduck]

Try reading your LTFT and SHFT while driving it at 70mph.

I have, its +/-2 for both LTFT and STFT under almost all conditions. (lifted, 32's, armored, almost 300k miles) I bet if you have your fuel injectors cleaned you'd be back close to 0...

-Charlie

 

[19963.4lsr5]

STFT does not have a P code. It drives the LTFT. I’m pretty sure that if You hit 20 on the LTFT you will code.


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[Malcolm99]

Interesting, truck has 200,000mi runs perfect, plugs look normal, I guess I'll try my spare wideband O2 ugeo one day and see how it runs and watch my injector duty cycle, so your telling me I must have bad injectors or fuel reg or fuel pump, I find that hard to believe, I also find it hard to believe a lifted 5vz-Fe with over sized tires will run without any compensation for LTFT at 70mph unless your off throttle and rolling down a hill, but happy to learn something new. STFT should be close to 0% at all times, I don't think STFT can adjust past 9% and LTFT can't adjust past 19%, I'm FED emissions using the same LT&ST fuel trim SGII code as Charlie.

Also note I'm getting 17-18mpg at -15*F on winter fuel, stock intake, 32.5" tires on heavy 4R TE 17" rims, 3" lift, 4.3ratio, hilly area, 70mph max speed usually, mixed backroads highway driving, seems normal to me. If I was infact running lean I would hope i'd get better MPG's than the low/normal range I'm getting since I have no intake leaks. IF I drive around at 50mph in flat country I get 20mpg easy.

 

[phattyduck]

You aren't running lean, the ECU is applying a fairly large amount of correction to remain stoichiometric. Likely, the high correction is because your fuel injectors aren't flowing like they did from the factory, so the ECU is bumping up the fueling to compensate.

Your MPGs are good and it isn't doing harm to the truck - the compensation range is there for exactly this reason. The point is that "0" is normal, and much beyond that means something is no longer running at factory specs.

-Charlie

 

[Malcolm99]

That could very well be, I did have the tank out a while back for the 99-2000 fuel gauge tsb, looked brand new inside, new oem fuel filter, truck is in pretty good shape, I suspect the tires rims and lift are causing higher than normal (expected) LTFT at 70mph, STFT usually runs close to 0-4%(+\-) but does see 8% +/- under extreme on off throttle position/load, as does the LTFT also does the same under those conditions. I guess I'm learning what's normal for a 5vz-Fe SGII reading, I always wondered if the refresh rate the SGII puts out is what the ECU is actually seeing, seems delayed on the SGII display, without a graph the SGII display didn't notice my faulty TPS drop outs.

 

[Malcolm99]

[MENTION=139000]phattyduck[/MENTION] thank you for setting me straight, it turns out my LTFT/STFT was screwed up and it was a bad MAF, after the above convo I pulled up MAF temp aswell and it was way off(more than expected from engine bay heat) I've cleaned it a few times before and recently with no change(I did note I couldn't get 1 of the MAF wires "resistor?" in the tube shiny clean) put in a Denso 197-6020, did not disconnect battery and took it for a drive, immediately it tried to go for +14% LTFT under load, and then corrected itself seconds later and now my LTFT/STFT is almost rock solid 0% and adjusts between +3 & -3 max after a 15min drive. I should note that before the new TPS I was seeing +19% cruising, then +14% afterwards, never got a CEL and the truck seems to drive the same after the MAF but I expect things will improve as the ECU fine tunes it's new FT values. Just thought I'd thank you for this and let others know my experience incase they dive into FT%. It seems the front O2 was telling the MAF it wasn't happy and was able to adjust accordingly and make the truck perform OK, but not ideal.

 

[19963.4lsr5]

[MENTION=139000]phattyduck[/MENTION] thank you for setting me straight, it turns out my LTFT/STFT was screwed up and it was a bad MAF, after the above convo I pulled up MAF temp aswell and it was way off(more than expected from engine bay heat) I've cleaned it a few times before and recently with no change(I did note I couldn't get 1 of the MAF wires "resistor?" in the tube shiny clean) put in a Denso 197-6020, did not disconnect battery and took it for a drive, immediately it tried to go for +14% LTFT under load, and then corrected itself seconds later and now my LTFT/STFT is almost rock solid 0% and adjusts between +3 & -3 max after a 15min drive. I should note that before the new TPS I was seeing +19% cruising, then +14% afterwards, never got a CEL and the truck seems to drive the same after the MAF but I expect things will improve as the ECU fine tunes it's new FT values. Just thought I'd thank you for this and let others know my experience incase they dive into FT%. It seems the front O2 was telling the MAF it wasn't happy and was able to adjust accordingly and make the truck perform OK, but not ideal.

I feel I should replace my TPS sometime. I run -2 to 1 for the LTFT in every driving condition but when my TPS is between 16-19%. it goes to between 3-6% in that range of throttle position. Usually a 3.


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[Malcolm99]

It actually makes sense the TPS would wear between 10-20% since that's where we use it 99% of the time, I was seeing the TPS jump between 10-20% and hard on/off throttle response to and hard shifts cruising, I thought is was the refresh rate on the scangauge display, but now I see 10-12-14-16-18% where as before it would jump from 10-20%, both my MAF and TPS where original 21yrs old, replaced with OEM TPS and Denso MAF, thanks again guys, I thought this was normal as I checked my friends 99 and got similar numbers, so it looks like his has similar issues and is also all original parts/sensors.

 

[DMiller]

Transmission temperature in Degrees C

Being a proud Canuck I figured I wanted all my gauges in C so I reached out to tech support and they came back with this.
Change the MTH from 00090005FFD8 > 00010001FFD8
It would appear it works.
I 3D printed up a bracket and a ball and socket joint out of PETG


//https://www.dropbox.com/s/9ye580erbt683mh/3D%20printed%20Ball%20and%20Socket.jpeg?dl=0

Here is it in place

//https://www.dropbox.com/s/sbwbdbib6hlrszw/Scangauge.jpeg?dl=0

I first tried using VHB double sided tape to attached to A pillar but ended up using some 6-32 threadserts.

I found the Ball and Socket in the heat did not hold angle as well as I had hoped so I applied some crazy glue to lock into desired position then took bracket out and drilled through ball and socket and ran a 4-40 machine screw to lock in position.

I may work on revision 2 in the near future.

Dave