E270Norway

I have some trouble starting my E270 03’. The display lights up like normal when turning the key except it dosent display what gear the gear selector is in. Nothing happens when trying to crank the engine. The ECU seem to have lost connection with the canbus and I cant access it with my diagnostic tool. I have checked all of the canbus connecting blocks x30/4,/5,etc and dont find any signs of corrosion. I have checked every grounding point I’ve come over for corrosion and I have had the ECU cloned and programmed a new unit, witch behaved just like the old one. I have tried to swap the gear selector, but nothing.
What is the next step? I’m pretty sure its a bad connection somewhere because now and then the car actually starts and seems normal, but after some time it seems to lose connection on the canbus and doesnt start anymore.
One of the fault codes is for the ignition, could it be broken? How can one tell?

Plutoe

from my perspective I would say you have a faulty ignition switch,but to prove that I would look to MB DAS for conformation or otherwise

CaliBenzDriver

Your faults scream bad CAN coms!

EZS Ignition switch needs to be resoldered and internal optical couplers dusted off clean but what I don't understand is both the ECU + TCU missing.

Any chance your ESL tiny motor got stuck?

I would hookup a scope to your CAN-C while connecting ECU + TCU.... there's got to be an obvious reason for ECU to not wake-up.
See that CAN signals do not get collapsed by any module.

The power manager is Front SAM.

E270Norway

I did check the ignition switch and cleaned off the optical connectors. The ESL operates like normal, unlocking the steering wheel when inserting the key.
I dont have access to a scope, only multimeter. Should I be able to measure any voltage on the canbus?
It seems like its the transmission control module that has trouble waking up. The few times I got the car to start, the TCM/TCU made a high frequent sound like it started operating. The TCM/TCU is completely quiet when the car doesnt start.
The thing is, the car should start with the TCM/TCU not even connected so I dont quite get what is going on.
Any idea of what to do next?

CaliBenzDriver

Being aware of all the above... I would then check power (and GND) to ECU/TCU, there a chance your SAM is not powering these modules.
A bad old relay would do that very well.