Why disconnect battery after mods??

[Ramm5.7]

I've seen in posts statements to disconnect the battery after some mods and am wondering whats the purpose for doing this?

 

[sbarron]

IN reality you should probably disconnect the battery BEFORE most mods....

That said, disconnecting the battery - if done correctly - "resets" the PCM, so it doesn't try to run the truck with the "old" settings.

 

[Ramm5.7]

So, I've installed a airbox add a tube and afe high flow filter. Should I have disconnected the battery or should I do it now, kinda late? It seems to run like a ***** ape when pushin the skinny pedal so hense my question. What constitutes a need for pcm reset?

 

[Ramm5.7]

And how long does battery need to be undone to reset pcm?

 

[sbarron]

Typically just a few seconds, most places mention 30.

 

[Ramm5.7]

Thanks sbarron. I guess i need to pay attention more....
Thats what SHE said.......lol

 

[travelinty]

Typically just a few seconds, most places mention 30.

I would say more like 15 minutes to make sure it gets a good reset. That's why it is better to pull it before you start.


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[Jimmy07]

It’s always good practice to unhook the negative cable from the battery if you’re doing anything where you are unplugging connectors. The reason is, if a connector has a terminal that gets power from the battery, and it were to accidentally touch anything metal on the truck, you would have a short to ground. “Resetting” the ecm has nothing to do with it. In fact, you’re not “resetting” or “clearing” anything in the ecm by unhooking the batteries. Maybe some readiness monitors, like if you had a CEL on at the time, it might go out, but after a few miles of driving, if the fault is still there, the CEL will be set again. The only thing adaptive is the transmission, and that won’t reset either unless you do a relearn though a dealer scan tool.

 

[Ramm5.7]

Ya, i know about shorts...lol, im confused about the "relearning" of the ecm? I've gathered from posts that disconnecting the battery and say, install a cai, then reconnect and drive that the ecm forgets how you used to drive with old air system and configures to new air system??

 

[travelinty]

Ya, i know about shorts...lol, im confused about the "relearning" of the ecm? I've gathered from posts that disconnecting the battery and say, install a cai, then reconnect and drive that the ecm forgets how you used to drive with old air system and configures to new air system??

Yes the pcm will forget the defaults of what you had been running and then try and relearn with say the CAI. If you don't key it relearn it will think your on a stock box and may not be running right. Really the best way is to use a tuner that will reprogram your pcm for that exact item you've added on.


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[Jimmy07]

The ecm doesn’t learn anything. It has a fixed program, or “tune”. It doesn’t remember, or care how you drove yesterday or a minute ago. It is constantly adjusting air,fuel, and timing based on input from your right foot. It doesn’t care what air intake system you put on it, as long as the airflow is within the sensor’s parameters.

 

[Ramm5.7]

The ecm doesn’t learn anything. It has a fixed program, or “tune”. It doesn’t remember, or care how you drove yesterday or a minute ago. It is constantly adjusting air,fuel, and timing based on input from your right foot. It doesn’t care what air intake system you put on it, as long as the airflow is within the sensor’s parameters.

Thats the way I understand computers. Why then the " disconnect battery to reconfigure ecm" posts. This is why im confused.
This then seems like pure opinion based on what?
Ecm has set factory parameters so how would said cai with more airflow, assuming still in sensor range, need to have battery disconnected?
For me it doesnt make sense unless you reprogram the sensor input totally by a "tune".

 

[Jimmy07]

Thats the way I understand computers. Why then the " disconnect battery to reconfigure ecm" posts. This is why im confused.
This then seems like pure opinion based on what?
Ecm has set factory parameters so how would said cai with more airflow, assuming still in sensor range, need to have battery disconnected?
For me it doesnt make sense unless you reprogram the sensor input totally by a "tune".

Who knows. Internet myth by people who have no idea how the ECMs in our trucks work?

 

[Ramm5.7]

Roger that