Hoping someone here can help. I am new to Mercedes but recently picked up a 2006 ML500. Car will not start. Turn the key, all the dash lights come up but when turning to position 3 I get nothing. No clicks no dimming lights. Checked terminals 125,123 and 124 in under hood fuse box. I only have 12 volts on terminal 125 with ignition on. Oddly sometimes I get 12 volts on 123 and 124 with ignition off but not always.checked fuse 14 for power near passenger door and have 12 volts there. I've checked all fuses and replaced both batteries. I've also had the EIS and keys checked out and they tested good, I had them cloned just to be sure and car still won't start.

I tried to connect a generic OBD 2 scanner to the port but get a communication error so i'm not able to read any codes.

 

How much did you pay for your scanner?

How long have you had the car?

Did you perform any repair prior to the problem?

 

Thanks for the response,

I have a Launch unit that i bought in the mid 2010's for about $1k and an icarsoft made for bmw's (and generic OBD) both power up but don't connect.
I've had the car about a month. I didn't perform any repairs but it looks like someone was tinkering with some wiring at the tail lights.

 

Check fuse #14 in the right side fuse box.

 

fuse 14 checks out ok. Dug into the system with my launch last night found I’m able to get into some modules. A consistent code is no signal from engine management module. I also found a little corrosion on the front Sam, pulled it apart and cleaned it up.I can communicate with front Sam with scanner still no start. Do ecu comms rely on front Sam?

 

Check the relay in the fuse box under the hood. There's also a fuse in there.