huffypuff Report post Posted May 20, 2015 Disconnecting a battery on today's vehicles can be costly whether it be your motorhome or toad. With today's computers control autos and trucks you will find many different computers (module) wired in to a complex system to control just about everything your vehicles does. All of these modules are programmed to do what it is needed for the vehicle for which it is installed. If the battery is disconnected at the wrong moment it could affect the programming of just about any modules in the vehicle. The first is the modules may have to relearn when the battery is reconnected or memory may be corrupted. Relearn is normal for many modules but when memory gets corrupted there is a problem. Sometimes it may require as much as a reflash of the module or even a replacement. How the avoid programming or memory problems is allow the modules to go to sleep before disconnecting the batteries. Modules are communicating with each other up to 20 minutes after the vehicle is shut off. If the communication is interrupted during that time information may be lost or corrupted. Sure there is back up power you can try but procedure with those can be tricky with vehicles be different than the other. The key here is to wait for 20 minutes before disconnecting the batteries so you can be sure all modules has went into sleep mode. If you don't it can be a expensive mistake. Share this post Link to post Share on other sites
jlandon13399 Report post Posted May 20, 2015 Thanks Ray. Very good information. Share this post Link to post Share on other sites
jleamont Report post Posted May 20, 2015 Ray, is this an FYI or did you just complete a course in the School of hard knocks? Share this post Link to post Share on other sites
obedb Report post Posted May 20, 2015 I hope he didn't because I have been to that school on other matters. It is not fun. I will be tinkering with my batteries tomorrow. I will heed his advice. Share this post Link to post Share on other sites
kaypsmith Report post Posted May 20, 2015 Thanks for the info Ray. These are some of the inhouse kept secrets to keep us depending on the manufacturers, so their pocketbooks can swell. Share this post Link to post Share on other sites
huffypuff Report post Posted May 20, 2015 Not school of hard knocks for me but was for others who had their vehicle towed to my shop. One example was a Lincoln Continental that owner had low battery. He wanted to be careful and remove the battery to charge. When he put it back in it required a replacement cluster. That required the keys to be erase and reprogrammed so the engine will start. Share this post Link to post Share on other sites
obedb Report post Posted May 21, 2015 Actually I thought that my diploma was a free pass on dumb stuff, but I am often called back for refresher courses.Later model Subarus including our Toad have keys with chips in them. You can only reliably buy one from a Subaru dealer and it must be programed for the vehicle that it starts. Our F-150 key has a chip in it. Local True Value sold me one, but it took a few minutes and $75 plus tax to have a spare. Pickup was OK. Have not lost and needed a new key for our latest Subaru. They are $200 or so. Share this post Link to post Share on other sites
huffypuff Report post Posted May 21, 2015 Lucky for me on the Lincoln I was able to reset the parameter of the modules and install the key chip codes using a tedious two key method. If you miss a step or hiccup so to speak, you have to start over. Share this post Link to post Share on other sites
jleamont Report post Posted May 21, 2015 I do not miss those days. As a Fleet Maintenance Manager now it's a headache in other areas, just not those. Share this post Link to post Share on other sites
