ML Rear Hatch intermittently fails to open
 

The power rear hatch on my 2007 ML320 fails to open without manual intervention. It fails when activated from either the key, button inside the vehicle or the latch on the hatch itself. When I inspected the mechanism, switches inside the hatch, all appeared to be in order. This leads me to wonder if I have a control relay issue. Of course MB holds any information regarding relays and fuses as a closely held secret. Can anyone help me in my quest to resolve this issue.

thanks

Check your battery voltage. I had that happen to me. Once I changed the battery my hatch has been flawless.

To check your voltage, with all doors, hood, and hatch shut, put key in 1st position and press R 3 times.

I suspect the hydraulic pump controller can't build enough pressure due to the low voltage and it times out.

Still at a loss to rectify the issue
 

Low voltage was the first thing I eliminated. It fails with the engine running or not. The battery has been replaced . . . . no help. The local MB tech and dealer have been scratching their heads as well. The next step is to try and sort out the relay mystery.

I can't believe the dealer techs cannot sort this out with STAR diagnostics.