BLM question

[myburb]

I think the long term trim resets when you disconnect the battery. Does it also reset when you remove and reinstall the chip. I am thinking in terms of 6395/7427.

[Montecarlodrag]

If you cut power to the PCM to change the chip (which you should) Yes

[brian617]

If you cut power to the PCM to change the chip (which you should) Yes

Is that true? I've change chips hundreds of times and haven't disconnected battery. It's my understanding there isn't much long term fuel memory strategy with this PCM. I would imagine its a rather primitive blm learn that is wiped every time the key is turned off. I'd be curious to know for sure.

[RobertISaar]

I'm somewhere in the thousand+ burn range and rarely have I disconnected power during a PROM change. the times I did were from being told it was necessary(probably the first 50 PROMs or so) or when I was patching in stuff to reinitialize values to their power-interrupted defaults.

it does have the advantage of resetting KAM/SAM fuel trims to 128, which is helpful dialing in fuel trims. could also do it via mode4 commands if the PCM supports it, since that will leave the learned IAC stuff as it is(though you could always change the calibration to end up with defaults where those learned values end up).