willscotmont

As an owner of an 05 I've had a number of the electronic issues you see discussed on the forum. "SERVICE STEERING COLUMN LOCK", "NO FOB DETECTED", "SHIFT INTO REVERSE", and my reverse lockout solenoid started functioning intermittently.
Recently I started having intermittent problems exiting the car and it displaying "SHIFT INTO REVERSE". This is the second time I have experienced this. The first time I remedied it by replacing both reverse light switches. This time, (a couple of years later), the symptom started happening again intermittently. So again I replaced both reverse light switches. The frequency of the symptoms became farther apart but we're still occurring.
I've always struggled getting my negative battery terminal connection nice and tight. When the new switches didn't fix the "SHIFT INTO REVERSE" problem I decided to replace my battery cable terminals. When I examined the terminals closely I discovered how to fix the existing terminals to get a tight connection. The 10mm nut on the terminal is coned on its bottom side. The cone goes into a chamfered slot in the terminal. When you tighten the nut the cone pushes on the chamfer to pull the connection surface of the terminal tight. The problem with its design is that that connection surface is a thin metal and it gradually bends outwards every time the terminal is tightened.
HERE'S THE FIX
Remove the nut and terminal from the battery post. Be careful not to loose the nut. Clean the terminal thoroughly. Use needle nose pliers to bend the cone shaped connection surface of the terminal inward. Make small gentle bends gradually around the entire surface of the connection. Reinstall the nut on the threads but do not tighten. Put the terminal on the battery post and press the terminal down hard as far as it will go. Now tighten the nut and the connection should be nice and tight. Since making this repair the "SHIFT INTO REVERSE" symptoms have not reappeared. 😎

GuyFromLeMans

One thing I noticed when I replaced my battery: I have NEVER EVER owned a car before (and I've owned more than a dozen) that required as much torque to be applied on the battery terminals in order to get a steady current delivery, as the C6 does.
I kept having to go back to the neg terminal and give it one more twist, hoping for the damn nut not to snap, until the power finally got to the car.

Amazing. And another C6 particularity I guess?....

willscotmont

GuyFromLeMans,
I know that my original post was too long so you may not have read it all. I too tried to overtighten the nut on the battery terminal to no avail. When the cone on the nut is tightened, it bottoms out in the "V" of the terminal's slot. It can't go any farther and because of the way it is designed it will not cause the terminal connection to beome tighter. If you still have a semi-tight terminal connection try the fix I described in my post. It worked great for me. I haven't seen "Shift Into Reverse" on my dash since making the repair.