I have a 2005 Supercrew.
5.4 3v
What exactly does disconnecting the battery "reset" ?

 

it set the pcm to base parameters. Looses all stored operational memory. Like for instance the data its been getting from the o2's the MAF etc are cleared and it starts of in a relearn mode getting fresh data from the engine sensors..

 

It clears the history of your driving habits along with any codes stored.

 

How long should it remain unhooked for the PCM to reset? I just did the intake mod on mine and let it sit unhooked for a little less than 10 minutes.

 

10 minutes is more than enough.

 

Boy, this thread looks familiar...
http://www.fordf150.net/forums/viewt...hp?f=1&t=897205 are more than enough. KAM goes volatile in less than 3 min. w/o KAPWR.

 

I agree. It is funny all the stories you hear about leaving it overnight with the lights on etc. to clear the KAM. There is more than enough load on the system to drain any charge without playing games.

 

Oh I dunno - a couple of 1 Farad capacitors on the supply rail may affect that.

With lights on - it's done in a matter of seconds - a guaranteed load.

MGD

 

It doesn't matter what you do or don't do with the lights or any other parasitic load. The PCM can't backfeed power out of the KAM - it has transistors & diodes to prevent it. So it wouldn't matter if you put a shorting bar from the KAPWR terminal of the PCM to a ground terminal - the KAM would stay alive for exactly the same amount of time.

Of course, adding caps to the KAPWR circuit would keep it alive longer, but why would you do that?

 

Steve - I'm not talking about backfeeding here.

If KAPWR is fed from the primary grid (which it must be) and that grid has supplementary storage attached (folks will do anything, lol), then as long as that storage takes to drain from normal parasitic load ( PATS, the clock, alarms, etc) that's how long KAPWR will be active (minus the time at which the lower threshold for RAM retention is reached).

Am I missing something?

MGD

 

Nope, you nailed it.

 

X2!
Makes sense and is understandable........

 

Yeah, the answers on the OTHER site kinda sucked.

 

One of us is. When did the OP mention supplementary storage? Even your answer assumed no mods to the KAPWR circuit, which has no storage, other than the main battery. And since this thread is about disconnecting the battery... The only "storage" is the capacitor inside the PCM that feeds the KAM, and it's isolated from loads outside the PCM by transistors & diodes. So again: no matter what loads are on the KAPWR circuit, the KAM will discharge the PCM's internal cap in the same amount of time.There's only 1 answer, and all the posts on this site say the same as the posts on the other site.

 

Any capacitance in the truck is storage and the residual voltage from that is seen by the computer until it drains away. If you had big 1 farad caps on your stereo they would provide voltage to the system until the charge dissipated. It is still less than 3 minutes and can be seen with a voltmeter. The diodes only come in to play when the KAPWR circuit is the highest voltage source remaining.