Afternoon, first I want to thank all participants on this site. The info that is shared is great.
Ok, a week or so ago I changed my fuel filter. In the "how to" instructions I found it tells you to remove the neg cable from the battery. Is this for safety reasons? Or is this so after you are done and it is replaced, the computer resets itself and make to required changes with the new fuel filter?
I was told by my neighbor, a 20 yr plus mechanic with Mazda/Ford, told me that removing the neg wasn't really necessary.
Bottom line, since I didn't take the neg cable off, should I go and do it which would allow the computer to reset.
If I should, should I only take the neg off and how long should I leave it off?
Thanks for any info.
Steve

 

I have never done that on any vehicle.

 

Removing the negative battery terminal is strickly for safely
reasons. When opening up the fuel system, you want to make sure you try to eliminate any sources of a spark.

 

The Negative battery cable is connected to the frame of the vehicle. The frame is an electrical conductor. It returns all the electricity from the component back to the battery, closing the circuit. When you remove the neg. cable, it opens the circuit, therefor nothing electronic in the car will be working; eliminating the chance of a spark that would ignite the fuel system (since it runs down the chassis. The "manuals" telling you to remove the cable is a CYA. Cover Your...

D Beames

 

Thanks for the quick responses. Just had me wondering after I read another thead in regards to cleaning the MAF sensor. The guy cleaned his MAF and his truck still had the same issues as before. One of the responses questioned if he removed the neg to allow his computer to reset itself based on the changes.
again, love the shared info
Peace

 

Actually the voltage travels from Neg to Pos. But you get the idea.
Jimmy

 

Removing the Negative Battery cableis purely a safety precaution in this instance.

However, I learning very quickly that, if I am working on any part of my vehicle, where I am expecting enhanced performance from the engine, it is bast to remove the Negative Battery Cable, to allow the Computer to reset & relearn.

I've seen many a vehicle computer still adjusting for malfunctioning symptoms, as though the old part was still attached.

After a while, the Computer will relearn, but why not start off fresh, instead of wracking your brain for days, wondering if your inept.

Its nothing to pull the cable, and let the Computer reset. Saves relearning time, and gives your ego a more timely boost.

Many of us look at vehicle repairs through the eyes of "Mr. Macho". Thinking, "I can do that repair without taking off the cable, I'm a big boy, I know what I'm doing, I won't short it out, and burn the vehicle to the ground".

I'm a Man!!!

Well, we hear you and understand the image thingy, but Guy's & Gal's,
"Remove that Negative Cable", "Reset the Computer"!!

First, always for safety purposes, don't ever forget "Static Electricity". And Second, if you are thinking, or expecting some performance enhancment results from your repair.

Maybe there won't be a dramatic change, but maybe there will be, with the Computer reset, to learn the improvement your repair may have made.

 

Am I right in stating that removing the neg battery cable only resets the codes in the system. Not the PCM itself? I thought you had to have a scanner to actually reset the entire computer. Disconnecting the battery cable only clears codes. Or so I htought.

D Beames

 

Hmmmmmmm. Now you got me wondering!

My understanding is that, the Computer itself, is reset to a "no trouble codes" mode, and if there are still problems, it will eventually relearn them, display them, so you can tell if you are actually making corrective repairs.

Maybe I should sit back and let a real live Electronic's Whiz add to this inquiry.

Until then, it may be best to ignore my initial response to this thread.

Elwhoppo to Whiz, come in Whiz!!!

 

Pulling off a battery terminal for any length of time should clear the PCM's KAM (Keep Alive Memory) and it's learned tables. Ford says this in the manual when replacing a battery.......

NOTE: When the battery (10655) has been disconnected or reconnected, some abnormal drive symptoms may occur while the powertrain control module (PCM) (12A650) relearns its fuel trim. The vehicle may need to be driven 18 km (11 miles) or more to relearn the adaptive strategy.



NOTE: When the battery has been disconnected or reconnected, volatile memory information will be lost. The affected systems will have to be programmed by the technician or customer. These systems include radio station presets, clock settings, and customer input keyless entry codes.

 

If voltage travels from negative to positive, then why do we always put the fuse on the positive wire. Seems to me that it flows in the opposite direction. The negative wire is the ground, the return.

D Beames

 

I see what you are saying. I thought that was the difference in A/C and D/C though. Alternating switched (why we use alternator's instead of generators) and D/C went straight through. Maybe I am thinking of something different. I can see how it would attract though. But have you tried to take a voltage reading of the Negative wire of something? Doesn't quite work. So that is why i though that the negative was the return.

 

oops sorry lxman when I got rid of your duplicate posts I got rid of the one I should have kept too.
sorry

 

The negative terminal (or ground) will have the sum of all the
currents from the positive terminal. The fuses are put in the
positive side, so individual circuits can be protected from
excessive current.

 

That's ok Dave, I think they got the idea