Jack Olsen

My trouble-free 2015 C300 has another small problem. I started getting an intermittent failure of the rear-view camera that has gotten worse and has frustrated my attempts to diagnose.

The problem is not a black screen. The camera simply does not deploy/drop, whether I put the car in reverse or use the menu controls to lower it for cleaning. In reverse, I get no change to whatever is on the COMAND screen.

Initially, it would fail a few times in a row and then go back to working correctly.

Over the past few weeks, the go/no-go ratio has gone from 90/10 good to 10/90 good.

I've looked at the wiring from the camera through the trunk, and it all seems intact and undamaged.

Things that SOMETIMES change its state from no-go to go:

1) Removing and replacing the 417 fuse.

2) Disconnecting/reconnecting the four-wire harness connection that is inside the trunk liner.

3) The passage of time.

I already did the transmission reset procedure to confirm that the system is getting a good reverse indication. It had no effect, and I suspect this isn't the issue since when it is not engaging in reverse, it is also not engaging when I use the menu options to lower it.

I've reset the COMAND system to no effect.

It could be a non-visible wire break, but I've had it go from operating to not operating with no movement in the car and no raising or lowering of the trunk. But that could possibly also be the result of some kind of reset taking place in whatever CPU is operating it.

I could replace the camera, but there is no corrosion on it, no apparent issues at all -- when the camera deploys, everything works perfectly.

I could replace the control unit, but as I understand it this requires a software reflash. Going to a dealership for diagnosis or re-flash is at the end of my list for fixing this. I'd rather solve it myself.

Any ideas?

Jack Olsen

Well, I think I've isolated the issue. I took out the trunk liner and looked at the different connections to and from the camera -- there's a video signal connector and also a set of four wires that power the camera, and then there are also two connectors on the handle/camera unit, one of which controls the actuator/motor that opens the trap door for the camera. All of it looked fine -- and I still got an occasional moment where the CPU seemed to have enough feedback/confirmation to lower the camera and receive a video signal.

But it was now maybe 1 in 10 times that the camera would work, and only after I unplugged/reconnected the four-wire connector for the camera and also removed/re-installed the fuse. Frustrating.

Then I took out the liner around the hinge itself (on the US driver's side). It's pretty apparent where the wire harness bends every time the trunk is opened or closed. I couldn't see any obvious fraying or break in the wires (and I don't have a diagram to know which color to look at more specifically), but I thought as a random try I'd make a splint for the section that had been bending -- just a stick and three zip ties -- and that seems to have solved the issue. The wire harness now bends elsewhere, but it looks as though there is a connection problem in the section I splinted. I'll keep driving and see if I get a failure again with the splint in place. So far, it's been good.

You can see I used a small dowel rod and three yellow zip ties to splint the section of cabling that was bending.