After loading a modified LS1Edit file I noticed how the fuel trims made a +5% jump.
From a scan I would say the MAF calibration has changed.
The thing is that I changed a completely differet thing (fan ON-OFF settings)!!

I double checked the program and every fuel related table is unchanged.

No error codes.

Is it possible to make something wrong while loading a file?
This is a 98 Trans Am PCM, LS1Edit software and interface come directly from Carputing and I used them xxx times without problems.

I just remember one thing: when the program has been loaded the software tells you to turn off the ignition, close the "Prog Load window" and quit LS1Edit.
After that I usually disconnect the interface and start the engine.
This time I've started the engine BEFORE unplugging the interface.

A couple of days later I re-loaded the same program and (MAGIC!) the fuel trims are now where they used to be.

How is it possible?? Is it a problem when starting the engine with the interface plugged in?


Thanks for any comment

Stefano

I can think of 2 possibles.

The LS1edit hardware interface is split into 2 parts.

Half has hardware that is supplied by the laptop's RS232 and it's voltage and handles RS232 protocol

The other half has hardware that is tied to the voltage of the car's ADLC connector and handle the PCM's functions.

When you leave the interface plugged in there still is a connection to the PCM and has not flushed the memory yet.
I could have just been without the memory flush that the engine then was tuned differently but old fuel trim stored averages.

Else without unplugging the interface the PCM had not thought transfer was completed and needed the battery of car disconnected for a few seconds.

By reflashing and pulling interface properly then all memory got properly flushed.

Always best to assure no voltage spikes to take any ADLC interface on/off before connecting to laptop with key off.

Also if in question is to pull one side of battery for a few seconds to assure flushing contents in PCM temp memory.

I see.

Is there some kind of fixed programm in the PCM that is used when something goes wrong during programming?
Like an emergancy program?

No there is no backup or mirror image of software.

Think of it this way, as your P/C has a TCP/IP connection, you make a session with a host then plug the LAN cable.

Same here as the LS1edit interface as still plugged in so it was still taking to the PCM so the session was not completed as power to interface still had it active.
PCM I suspect then does not do a normal clearing of memory where averages like LTFTs are so they are not flushed out when starting engine has the old averages where normally they are erased after a flash is done.

Reason people have made the PCM into a brick is for whatever reason the session is broken during or right after flashing leaves he flash memory in a non complete state or the data no longer matches the CRC checksum the PCM no longer has a valid segment 1 software.

Really? Can you damage the PCM because of a programming mistake?
Is there a procedure to save the situation when something happens during programming? For example when the HD has a crash or the laptop battery is down?