Starter not working

2006 MERCEDES BENZ S600
97,567 MILES • 5.5L • V12 • TURBO • 2WD • AUTOMATIC
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C.A. GRIFFIN III
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Car was draining batteries over night. Checked all fuses. Current draw was happening when car off. Changed battery twice. Checked SAMS fuses, relays. Then unhooked ECU. No loose parts and didn't smell burnt so Placed back in

Now with good battery car starts. Doesn't appear to drain as much as battery is still okay in the morning though there is still 1.74amp drain in off state.
When it runs doesn't run like V12. Then after it warms up then it misfires.

Come back later no start but have good battery power. Checked Starter relay. Jumped pins 87 and 30 (i believe) still no start.

Connect OBII scanner to read ECU.... take a while but when it does connect, then the car will start.
Once or twice the starter just spins, Sometimes it starts right after the scanner connects. Weird it takes the scanner tool to make car start.

Am I having ECU issues?
Lights on car ESP, Distronic, SRS sometimes say display failure.

Was wondering if starter or ECU could be current drain, rough running and when it warms up causes a disconnect in ground or something.
Dec 14, 2019 at 10:11 AM
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STRAILER
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Hello,

Yes the ECU could be draining the battery and causing the issues. To be sure lets do a CAN scan which is the future of automotive repair. you can get a CAN scanner from Amazon for about $50.00. here is a video to show you how:

https://youtu.be/InIlnsjOVFA

Here are instruction on how to replace the ECU in case this ends up being the issue. Check out the diagrams (below). Please let us know what you find. We are interested to see what it is.
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Dec 16, 2019 at 1:44 PM
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C.A. GRIFFIN III
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I have unhooked the ECU and still Battey drains over night. One thing I found is I can hear a click in the rear heater control valve switching every 10-15 seconds long after the car is off. What is connected to this valve that tells it to energize the coils?
Dec 20, 2019 at 9:28 PM
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STRAILER
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This would be the HVAC controller lets try unplugging it to see if the battery drain goes away. this guide may help as well:

https://www.2carpros.com/articles/car-battery-dead-overnight

1 Remove cover from center console (5)
2 Disconnect connectors (2, 3 and 4)

NOTE: Connection and disconnection aid.

3 Unscrew screws (1)
4 Remove incremental adjustment motor electronic control module (N22/5)
5 Install in opposite order.
6 Synchronize incremental adjustment motors.

Check out the diagrams (Below). Please let us know what happens.
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Dec 21, 2019 at 11:35 AM
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C.A. GRIFFIN III
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Several issues going on.
I unhook battery at night to stop drain for now.
When hooked back up... key has to be in and turn to on position for about 3 minutes before car will start. Before that it says noting though everything is on.
Sometimes in that period the radiator fan would come on then go off and then I would know the car can start.
Once started I see 14v from alternator for about 20 mins before it slowly goes down to around 12.3v
Car then starts to very noticeable misfire
Even when first started and 14v is present, car still doesn’t feel like all 12 cylinder power. Like something hold back horsepower.
Makes we wonder what’s the real source as I may be chasing issues but not the source of the problem.
Jan 12, 2020 at 5:11 PM
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STRAILER
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It sounds like the SAM module is out. To be sure, lets do a CAN scan which is the future of automotive repair you can get a CAN scanner from Amazon for about $50.00. here is a video to show you how:

https://youtu.be/InIlnsjOVFA

Please run down this guide and report back.
Jan 13, 2020 at 11:52 AM