Dodge/Chrysler/Jeep NGC3 PCM Fuel Trims Reset

[TunedByNishan]

Hey guys,

Wanted to share some valuable info for anyone who hasn't really tuned with the NGC3 PCM before.

I've worked with the NGC3 PCM in multiple vehicle applications thus far and have had great experiences using HP Tuners to do so.

One thing I have discovered is that if you want to tune the VE map in Open Loop, simply setting the Closed Loop feedback control to a very high unachievable ECT to disable closed loop operation is not enough.

When doing this, the NGC3 PCM will only disable STFT O2 feedback.

The PCM WILL still use stored (learned) LTFT's in their respective RPM & Pressure Ratio breakpoints.

If you do not recognize this, you WILL be tuning your VE map with a percent correction already being applied.

There is no fuel trim reset control in VCM scanner to reset and zero out the stored LTFT's.

You must do a PCM reset by disconnecting the battery for 5 to 10 minutes.

Once you reconnect, all stored LTFT's will be reset and zeroed out.

You can now truly tune in open loop at this point.

[doc350]

does reflashing the car not reset the adaptives? good info though.

[TunedByNishan]

does reflashing the car not reset the adaptives? good info though.

Correct, re-flashing does not reset the fuel trims at all even if you do a write entire.

If you disable closed loop and re-flash, the STFT's will disable and not react to O2 feedback, however the learned LTFT's remain active, they just won't learn any further.

Only disconnecting power to the PCM will reset all stored trims.

Something to keep in mind when tuning in open loop.

[BlownHemi]

Great info Thanks