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2009 smart fortwo won't start

12371 Views 24 Replies 9 Participants Last post by  wahi
I have a 2009 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 woek, 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 thebrake lights do not work. I have tested the battery and I get 12 volt, battery passes a load test. The 3 fuses in the battery compartment are good, all the fuses in the fuse box are good. I have removed the brake light switch and it tested good. When I turn the key on I hear what sounds like a relay click in I think the fuse box and one that clicks back in the engine compartment. When I tun the key to start I hear another relay click under the dash. I have tried reseting the cluster and still nothing. Can anyone help?
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I have removed the brake light switch and it tested good.
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The brake switch does not have any power going to it.
I spoke with a Benz mechanic on the phone and he seems to think the ignition switch is bad and not communicating with the computers but he can not say for sure without havinh the car.
I realy don;t want to haul the car 150 miles to be at the mercy of a dealer.
The brake switch is under the car in a compartment and is activated by the brake pedal arm. The switch itself is a double pole double throw type. There is 4 wires on this switch, 2 are suppose to be 12 volt going to the switch.
In the non braking position one set of contacts are connected and sends 12 volt out, when the brake pedal is depressed the switch disconnects that set of contacts and connects the other set of contacts to send 12 volt out via the other wire which I assume goes to the shifter release and probably activates the brake lights and who knows what else..
Since I do not have 12 volt getting to the switch the bad ignition switch idea makes since, as the ignition switch tells the SAM and the ECM what to do. I can get an ignition switch from a wrecked smart but it will not work with my car or key. I would still need to take the car to a dealer to have the ignition switch programed to the car and my key programed to the switch but I don;t think a programed key can be re-programed to a different car so I would need to buy a new switch. I can also get a switch with key from a wrecked smart but a dealer would still need to program the switch to my car. Before I did any of this I would want to make sure the switch is the problem. I have gone over every inch of wiring and every connector I can get to without taking the car completely apart. Nothing on evolution concernig this problem.
I was also told by a local mechanic that the key could have lost sync. with the switch.
Do any of you have a spare key for your smart that is just the blade with no fob, this type of key would be for unlocking the door and it will fit into the ignition but will not start the car.
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When the ignition switch is activated the switch sends out data signals to all computers ( the instrument cluster is a computer as well ) on a few different data lines leading off of the switch which then tells the computers to power on.
In some cases, one or more of the data lines can fail in the switch or they may all fail.

If someone had a key that is just the blade and put it in the ignition and turned the ignition on to see if the instrumrnt cluster would light up or not.
Yes it is my understanding that the ignition switch turns the SAM unit on and off and the SAM unit feeds power to the other components.
I have had the SAM unit loose from the car to check the fuses on the back side but did not completely remove it. I see there is a good article over on evolution about the sam unit. I will remove the SAM unit and check all the plugs for corrosion and burnt pins. I have checked and there is 12 volts at the starter, I jumped the starter terminals and it did activate the starter.
I know the SAM is getting power because some things work like the wipers, blower motor, headlights, tun signals. I will check the instrument cluster fuse which I believe is fuse 12 to see if there is 12 volt there.
I removed the SAM from the car and did not see any burnt or corroded pins or plugs. I took the SAM apart and could not find any cold solder joins or corrosion anywhere. I did see where here had been water in the SAM at one time so maybe it shorted something out.
I have been told by MB I can not take a SAM unit from a different smart car and put in mine, it won't work. Has anyone tried this?
Thanks for the info jwight, I will give them a shout.
person with smart car wont start, mine doing same thing did you ever figure it out, mine had a cup of water spill on the dash, right over the fuse box then quit
No I have never determined why may smart won;t start, I thought it was the SAM unit so I sent the SAM unit,ECU, instrument cluster and a key to SOS diagnaustics and they put my modules in there test car and everything worked fine. my ignition tests good, the imobilizer ring is good. I have narrowed the problem down to the CAN Bus I think.
The Smart cars are notorious for having leaking windshirlds, seems the windshield leaks and lets water get on the SAM unit and shorts it out or corrodes the conections and causes the SAM unit or connections to fail. In your case spilling a cup of water onto the SAM unit (fuse box) if the car quit immediately then the water probably shorted out the SAM unit. This is just my opinion as I am not a professional Smart mechanic.
thank you for replying so fast, im sorry when I said it quit right away it did not it made it home the when tried to start again next day would no start. can you tell me what the CAN BUS is, thanks
CAN stands for central area networking, and bus is a group or cluster. an example of a bus would be your fuse bus. CAN was developed by Bosh and consists of 2 wires that connects all of the modules in your car such as the ECM, TCM, SAM, instrument cluster, ABS module and so on. Each module receives and transmts signals through these two wires. Each module has its own bianary code so no other module will get a code intended for the module the coded signal is intended for. Every module communicats with each other over these two wires. Each module receives a command from the SAM unit and responds back to the SAM unit. The 2 wires consist of a CAN high and a CAN low, the CAN is connected to the OBDII port and the CAN is what a code reader or scan tool communicates with when pluged into the OBDII port. Any module that malfunctions has the info stoed in the CAN BUS as to what the malfunction issue purtains to.
Since water was spilled on your SAM unit that would be the first place I would start to look for the problem, however you can not just plug another SAM unit in, it will not work because the SAM will need to be programed to your car which can only be done by a Mercedes Benz dealer or someone with a Star diag tool loaded with Mercede Benz software. If you took the SAM unit from a wrecked Smart and put it in your Smart it would not work without being programed to your Smart. The only way I know of to replace any of the parts without programming is to get the SAM unit, ECM, instrument cluster and a working key from another Smart and put all the modules in your car. this could get expensive but it will be expensive to take your Smart to MB dealer. Another option would be to contact SOS and send them your SAM unit, ECM, instrument cluster and a working key, They can test your modules in their test car, if they determine your SAM is bad they can provide you with a SAM unit and program it to your car. They do not need your car to do this, but they do not test the modules for free, I think with shipping I had to pay around $240.00 just to have them test my modules and then found that my modules were all ok. But at least I now that the problem is somewhere else.
It might also help if you would explain in exact detail what your smart does when you turn the ingnition on and what happens when you try to start it.
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