How to reset long term fuel trims?

[Hulkss]

E38 ECM, Pontiac G8 GT

How do I find and reset the long term fuel trims?
Searched and could not find it.

[swingtan]

Find: Log LTFT's. If they are anything other than 0%, you've found them.
Reset: Perform a PCM reset or disconnect the battery for a while. This is the only way to reset the long term trims.


The E38 will retain LTFT's across CAL re-flashes, so you need to be very careful when making fueling changes and running LTFT's. Even more so, if you disable LTFT learning, but leave LTFT correction on. In this case the LTFT's will never change and be stuck at whatever they are on.

Simon.

[mr.prick]

IIRC there was the option to reset them after a reflash in the tune.exe properties. :nixweiss:

[68problemchild]

How do you perform a PCM reset?

[Hulkss]

How do you perform a PCM reset?

The only way I've been able to reset the LTFT's is by a PCM reset.
The only I've been able to reset then PCM is by disconnecting the battery.
This is lame.

I'm not sure how long an E38 needs to be disconnected for a reset.

Any body actually know the minimum disconnect time to guarantee a reset?

[swingtan]

IIRC there was the option to reset them after a reflash in the tune.exe properties. :nixweiss:

This is available for the LS1 PCM but not the E38...yet....

To perform a PCM reset...

Bring car up to normal operating temp.
Turn ignition off.
Remove ECM main fuse.
Turn ignition to "on", do not start.
Wait for system check to complete, numerous errors will be detected.
Turn ignition off.
Replace fuse.
Turn ignition to "on" and wait for system check.
For the LS1 controller, if you want to bypass the idle relearn procedure, press the throttle to the floor more than 6 times.
Start the engine to ensure all is OK.


You may need to clear DTC's on the G8/VE range.

Simon.

[mr.prick]

Is it? :nixweiss:
I can't find it or it was my imagination. :hihi:

I know the option to clear LTFTs (LS1) is in the scan.exe

[izaks]

For E38, Select DVT, then Fuel System, and then click on Fuel Trim Reset

[swingtan]

For E38, Select DVT, then Fuel System, and then click on Fuel Trim Reset

That only works if you have the laptop. BBL/BBF has no way of resetting the trims. It should be an option when flashing a tune, which you would want if you had altered the fueling in any way.

[joecar]

Is it? :nixweiss:
I can't find it or it was my imagination. :hihi:

I know the option to clear LTFTs (LS1) is in the scan.exeHi Mike,

Goto DVT tab, select GenIII LS1 99-08 PCM, goto Learning subtab, see Fuel Trim Reset.

[Hulkss]

For E38, Select DVT, then Fuel System, and then click on Fuel Trim Reset

Thanks, after specifying the target controller (Gen IV V8, V6 E38 ECM) this looks like it will work. Have not tried it yet.
Should this be done with the engine running, or just with ignition on, or doesn't it matter?

[joecar]

Doesn't matter.