Smart 451 MHD won’t start

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Hi all 

my 451 MHD has developed a problem lost all light on cluster. No ignition and no communication to ECU. 
sam unit does click when trying to start with key. I have already changed ECU,Sam and cluster from another MHD and still got same problem. 
I have a 2011 Smart Fortwo coupe that will not start. when I turn the key on there is no lights come on on the cluster, tern signals work, radio works, lights work, wipers work dome light works, but nothing comes on on the instrument cluster and I can not move the shift lever out of park. Also the brake lights do work. I have tested the battery and I get 12 volt, battery passes a load test.
all the fuses in the fuse box are good. When I turn the key on I hear the relay click in the fuse box and clutch actuator in the engine bay.
When I tun the key to start I hear the starter relay click from the Sam. I have tried reseting the cluster and still nothing.

can anyone please help with some advice on what I may be missing. 

Edited by Ram3o
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First welcome to the site and club.....always great to get new members even if they simply need advice...lol


Have you tried all grounding pin locations, there are many amd also the braided ground strap running from engine to body.  I don't know the locations of the grounding pins for a 451  but they are a problem on the 450, you must take them apart to clean between each eyelet.....sorry to say.


Then check the braided wire running from starter to starter solinoid.....also check spade connector, the trigger wire on starter itself.  I'd also check for perfect connection between main power wire to starter and the starter itself for corrosion.   I have plenty of suggestions for the 450 but very few for the 451, sorry.

Also when you swapped out the ECU, Speedo and SAM did you do it as a bundle or singularly?   IF done one at a time they must be taught to speak with each other using a STAR machine......it is a complicated procedure but possible.

Again welcome and hope any of this helps.

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Hi willys

thanks for the wonderful welcome. 
everything is grounded and clean the MHD module don’t have a conventional starter motor it’s the starter and alternator in one. 
also yes I swooped all at as a bundle as I was aware that if ones was to be replaced I would need to program it to the car and I don’t have the software to do this also there is no communication between the obd port to the car only getting power so now I’m thinking it’s a canbuss issue but cannot be too sure as I have changed everything but the ignition switch it’s self 

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