jburn7777

I have a 2007 s550 ( 221). Wont crank, wont start all lights and radio comes on.. things ive done:

1. Checked all fuses ( In all locations..all good)
2. Checked all relays ( replaced one bad for Air compression)
3. Replaced starter relay (OEM)
4. Replaced batteries ( both front and back are new)
5. Replaced starter
6. Replaced key batteries ( idk why..just knew they were a year old)

Still turn the key and get nothing.

tepelena

I'm sorry you're experiencing this issue with your S550. Since you've already replaced the fuses, relays, starter, and batteries, the problem could stem from a faulty ignition switch, issues with the vehicle's immobilizer or anti-theft system, or a malfunctioning ECU. Wiring problems within the starting circuit or a defective clutch safety switch (if your vehicle has a manual transmission) could also prevent the engine from cranking. Additionally, there might be issues with the key fob communication or sensors related to the starting process. Another thing you should start is driver authorization. You should probably run a full system scan. There should be fault codes on at least one or more control modules related to this. You will either need to take it to a mechanic, but if you want to figure this out yourself, then you will need to get a full system scanner. the "youcanic full system scanner" is very good at diagnosing all systems, and there are other scan tools that can do this. Just be careful to use a full system scanner or you may scan the car and see no fault codes, as some scanners cannot read all vehicle systems. If the scan doesn't apply to the issue, you can consider other troubleshooting steps. I'm here to help if you need more assistance!

MBCO

I have this same engine in my 2007 SL550, and experienced similar symptoms. With no codes displayed on MB DAS Xentry, my Indy put a bag of Ice on the ECU. A few minutes later it started. Repaced ECU and problem solved, $$$, north of 2500.