Computer Program Removed

[EquatorHeat00]

When you disconnect the battery, and scan your cars computer for trouble codes will this remove the programming from a handheld programmer/return it to stock settings? (HPP3)

[Injuneer]

No.

Disconnecting the battery clears the volatile memory. That consists mainly of the "learned" data, like long term fuel corrections, learned idle position and stored trouble codes. It does not clear the memory where the program is stored. When you scan a computer, is has no affect on the volatile memory unless you deliberately "clear" a trouble code (if your scanner has that capability), and has no affect on the "program".

[96Camaro]

Would it clear the memory if you were to just unhook the computer cables without disconecting the battery?

[Kevin - Blown 95 TA]

That wouldn't be too bright. It's protected pretty good against transients, but you run the risk of removing the main power while signals and drivers are active, and that is never a good thing. But, the power to the PCM is fed through those cables, so it would ultimately do the same as Injuneer stated above.

[Injuneer]

As pointed out, disconnecting the harness connectors without pulling the "ECM BAT" fuse can damage the PCM. One you pull the connectors off, you have removed all power to the PCM. But you will only lose the volatile memory - long terms, codes and learned idle. All the "programming" is in non-volatile memory and will stay there forever, or until a transient from mistreatment of the PCM renders it inoperative.