I have been reading posts about disconnecting the battery to reset the computer on our trucks. When my truck was in for check engine light being on they reflashed my computer. If I disconnect the battery will the computer keep the pcm update or will it go back to factory program?

 

Disconnecting the battery should not affect the PCM.

Keep in mind, when you do disconnect the battery, don't just disconnect and then reconnect. Let it sit for 10 minutes or so, then reconnect it. A simple disconnect-reconnect does not give it enough time to even realize there was a loss of power.

 

You could leave the battery disconnected forever, I am almost certain the memory of your PCM is a solid state flash type memory that is unaffected by loss of power. No power to it simply causes a reboot which makes it relearn the trucks variables such as intake, and exhaust.

 

Thanks Tuff & Eddy.

 

I disconnected the negative terminal on my battery while putting on my Airaid intake (they show it as step 1, and I'm a "follow the instructions" kind of guy). Prior to doing this, my truck ran great and shifted fine. After, it idled higher and changed all of the shift points on the trans (started in too high of a gear and almost instantely shifted into overdrive in every situation). I was pissed. I called Airaid and they recommended that I diconnect it again for at least 2 hours so the computer could "re-learn" the new air flow. I did this. It changed nothing. I knew that changing the air intake wasn't going to directly impact how the trans shifted. I had to have lost my programming and been left with whatever supercrap EPA enforced base line programming was hardcoded into the system. I finally got it into the dealer and had them reflash it, and it helped quite a bit, but it's still not what I remember it being. The second that the Superchips unit hits the street, I'm buying one. I'm putting my faith in the aftermark to get it "right" and then I won't have to worry about losing it again because I'll be able to do reload it myself. Without a programmer, I would NEVER unplug the battery if the thing is running and shifting half decent- regardless of what anyone else tried to tell me.

 

hmmm, perhaps i may rethink disconnecting the neg. battery....didn't do it when i put the flowmaster on, was thinking on doing it when i buy the drop in K&N.

 

So this must mean that if you have a battery failure i.e. dead battery, that your truck will never run the same again. I don't buy that. I do think, that some trucks may have a problem but lets not say that they all do, ok. I would think if the battery problem was as wide spread as indicated here, this web site would be full of angry owners. Oh by the way I keep a trickle charger on mine 24 hours a day with a gas powered generator backup for when I park it away from home. Come on guys...

 

Carpenter, you're right. The programming in the PCM will never be lost (short of a hardware failure) unless it is overwritten by flashing. It DOES have an adaptive learning strategy that will start from the beginning when the battery is disconnected (as noted, for more than a minute), this is by design, so every time you disconnect the battery long enough for the caps to leech, you will have to wait some time for the PCM to learn. Disconnecting your battery and changing a your air intake, and then blaming only the PCM is only looking at half the problem. Why would you not think that the changed air intake might have some affect? With modern powertrain controls, almost any change can have profound effects.

 

Look at it like you would a regular computer.

If it gets all messed up for some reason, then reloading the OS usually makes it better. But then, it's sometimes hard to get it back exactly the way you like it.

If it's running fine, don't try to fix it. Sometimes you just gotta know when to leave it alone.

In rocketjock's case, he just followed instructions. But now he is having a hard time getting it all back the way it was. Perhaps those instructions should have warned him.

Between my Ranger and my first Taurus, I've been through it 5 or 6 times due to dead battery or overseas shipping. A friend had told me if it ever happened, to be sure to drive exactly like I normally did for a few days. Some extra accelleration, or lack of it, can result in the computer learning something other than you want. Each time I had better luck than rocketjock.

My advice is not to reset the computer if the vehicle is running the way you like. If it seems all messed up, then reset it - but drive the truck like you want it to learn for a few days.

 

OWNER’S GUIDE F-150

Maintenance and Specifications pg.235

Because your vehicle’s engine is also electronically controlled by a
Computer, some control conditions are maintained by power from the
Battery. When the battery is disconnected or a new battery is installed,
The engine must relearn its idle and fuel trim strategy for optimum
driveability and performance. To begin this process:

1.With the vehicle at a complete stop, set the parking brake.

2.Put the gearshif in P (Park) (automatic transmission) or the neutral position (manual transmission), turn off all accessories and start the engine.

3.Run the engine until it reaches normal operating temperature.

4.Allow the engine to idle for at least one minute.

5.Turn the A/C on and allow the engine to idle for at least one minute.

6.Drive the vehicle to complete the relearning process.

yada, yada, yada!



There’s all kinds of interesting stuff in the OWNWE’S GUIDE