Originally Posted by majfrizz
on GMs Malibu/Terrain/Equinox the owners manuals say pull three different fuses. On the full size trucks, these trucks, and Yukons they tell you to disconnect the negative. No one knows why.
I could not begin to tell you how many posts that I have read on this and other towing forums that explore the mystery of disconnecting the negative battery cable. I think that the dealers do not know and the manufacturers do not want to admit is that there is no definitive reason that we are all seeking.
My theory is that manufacturers know that folks flat tow their vehicles and in many cases modify the existing wiring to accommodate brake systems and lighting. This could introduce the remote potential for a "sneak" circuit that could, in some way, damage the vehicle. Most of the newer 4WDs utilize electronic controls for their transfer cases and disconnecting the negative battery cable is the safest approach from a manufacturers standpoint. It is really not doing anything much different from turning the key to the "Off" or "ACC" position. If my theory is unfounded, it would be nice for an industry expert to stand up and give their side of the discussion.
All of this reminds me of the reason we are asked to turn off cell phones when we fly and have been doing so for years. The truth is that it was a measure based on a theoretical and unproven concern. There is no definitive reason and there most likely will never be one.
I do commend redcolorado for testing the waters and proving my point by being brave enough not to disconnect the battery when towing.