Hey everybody , I’m new to the CrossFit e world and could use some help, I recently picked up a07 convertible pretty cheap because the owner lost the key, I purchased a used ignition w/key the Skreem module and ECM to match, after installing them it would turn over but not fire , none of the dash light or fuel pump would turn on, it would do this two more times and then not at all , I know that is a screen issue, hooked up the alter scanner and it said no connection to ecm, I put the OEM ECM back in, dash light and fuel pump work but it won’t turn over, pulled the RCM and nothing looks dark but it does have a bit of a burnt smell, any advice on where to start would be much appreciated, the car is a 07 convertible , auto trans and has 75,000 on it

 

So the starter engages twice and then won't engage again with the replacement ECU/SKREEM and key?

And with the original parts in the car you get no starter engagement at all?

THat's not making logical sense. But since you dont know for sure the history of the car OR replacement parts, I'd start with a voltmeter and the service manual wiring diagrams and see what you have and don't have (voltage wise) on the outputs of the RCM as well as ECU outputs to the RCM and pulse modules. The fuel pump enable comes from the ECU but you won't get that unless the RCM first provides "Engine control relay" output to the ECU. On one hand, it sounds like the RCM is bad, but it cant be since you can make the ECU light up and engage the starter with the replacement SKREEM and ECU.

If you are not experienced with electrical troubleshooting, you will be soon. GO SLOW at this and take your time. Keep notes of what you find with the replacement modules in the car versus the original parts.

Of course, the EASY way out would be to mail the SKREEM, ECU and ignition cylinder to the guys at The MSS and let them make a new compatible key (and even do the SKREEM mod). This business of buying donor car SKREEM/ECU/KEY can work, but it can also be a nightmare if the parts you buy are not actually working. And how do you KNOW they work?

If it was my project, I would have just yanked the original SKREEM, ECU and Ignition switch and sent them to the MSS. We all know that they would send back working parts the first time.

 

Hi lilyeti,
if you do go the way of probing everything, I would suggest buying connector back probes - they make doing the job so much easier (something like ). Have you tried disconnecting and reconnecting the battery? if it's a SKREEM issue, that should reset the error, and the common symptom would be a start for a couple of seconds for 3 times, and then no crank. If you search the forum for no crank, you'll find tons of ideas and causes. Some of them have what the measured values/voltages are from each pin on the RCM, and how to check the CAN BUS.
Good Luck, keep us posted.
-Jerry

 

THe log shows he has not been back to see our posts. I've taken some time, I think I see whats going on. Perhaps this will help when he checks in again.

1) He buys the car, on the basis that the "key is lost".
2) He buys an ECU/SKREEM and key from a donor car (not a good idea, but some have had to resort to this).
3) The car turns over but wont run. He gets two cranks then nothing. This means he bought a non-matched set or a set with a bad SKREEM. BUt it also means the RCM is good cause the starter does engage.

4) Putting the old parts in, he gets no crank at all but this is, again, NOT the RCM cause we already know the RCM is OK.

Conclusion:
He bought a non-matching key/SKREEM/ECU set or a set with a bad module.
Other conclusion: THe original ECU appears to have a problem.

REcommendation:
He call the MSS and talk to James and send all items to the MSS and let them return a working set to him once they fix one set or the other.

That is how I'd do it.

 

Yup!

 

Lilyeti, I think you may have the same problem as my 2004. I searched online and found a couple of articles that said the culprit is likely the K40 relay. The fix is to check solder points or buy a new K40 relay. I can't find any Mercedes Benz specialist in the Phoenix area that wants to work on the car. So it looks like I may have to do the troubleshooting/fix myself. If you do try fixing the K40 and it works, please send me a text at 480.991.1111. Thanks Mike