C300 Luxury. No crank with good battery. Advice needed.
Thread Starter
Junior Member
Joined: Jan 2024
Posts: 27
Likes: 7
C300
C300 Luxury. No crank with good battery. Advice needed.
Hello everyone
Need some help here, my car has had a couple of no crank events in the past 4 days. Both drives were similar, short (less than 5 miles) drive normal city speed, park it for 10-20 min and when I come back the vehicle did not crank.
IP illuminated it, for a brief period and ESP error message was diplayed. I tried around four times, and in the 5th or 6th time, I open the driver door, and did a Lock/unlock cycle and then it cranked and started like nothing happened.
I initially tought it was the battery, but battery is fine (checked SOC is 85% and 12.5V) and there are no DTC for low voltage
I then checked for DTC, and found quite a few. Some are related for sure.
ECM
0746 Mixture to high on Cylinder bank 1
0750 Mixture too hight on Cylinder bank 2
2092 Mixture too rich at idle on cylinder bank 1
2096 Mixture too rich at idle on cylinder bank 2
2289 Power Supply at the input of contro unit "combustion engine" has a malfunction.
Front SAM
B212172 Relay 1 Circuit 15 has a malfunction, Actuator does not close
OCP
a15F11 Relay 1 Circuit 15R has a short to ground
Has anyone seen this issue with the Circuit 15 and a no crank? I have found very few information about it. And I am planning to buy some schematics.
There are other ECU complaining about lost comm with the "Combustion engine" module. Like the IPC and ESP.
Relay 1 seem to be working. and on the fuse box there is no short to ground, or not in the first inspection.
I was able to clear the codes yesterday, and drive the vehicle park it, and no issues. So seems to be intermitten.
Any pointers are appreciated it.
And if you know a good source for electrical schematics and repair manuals is appreciated.
Thanks!
Need some help here, my car has had a couple of no crank events in the past 4 days. Both drives were similar, short (less than 5 miles) drive normal city speed, park it for 10-20 min and when I come back the vehicle did not crank.
IP illuminated it, for a brief period and ESP error message was diplayed. I tried around four times, and in the 5th or 6th time, I open the driver door, and did a Lock/unlock cycle and then it cranked and started like nothing happened.
I initially tought it was the battery, but battery is fine (checked SOC is 85% and 12.5V) and there are no DTC for low voltage
I then checked for DTC, and found quite a few. Some are related for sure.
ECM
0746 Mixture to high on Cylinder bank 1
0750 Mixture too hight on Cylinder bank 2
2092 Mixture too rich at idle on cylinder bank 1
2096 Mixture too rich at idle on cylinder bank 2
2289 Power Supply at the input of contro unit "combustion engine" has a malfunction.
Front SAM
B212172 Relay 1 Circuit 15 has a malfunction, Actuator does not close
OCP
a15F11 Relay 1 Circuit 15R has a short to ground
Has anyone seen this issue with the Circuit 15 and a no crank? I have found very few information about it. And I am planning to buy some schematics.
There are other ECU complaining about lost comm with the "Combustion engine" module. Like the IPC and ESP.
Relay 1 seem to be working. and on the fuse box there is no short to ground, or not in the first inspection.
I was able to clear the codes yesterday, and drive the vehicle park it, and no issues. So seems to be intermitten.
Any pointers are appreciated it.
And if you know a good source for electrical schematics and repair manuals is appreciated.
Thanks!
Junior Member
Joined: Feb 2025
Posts: 18
Likes: 4
From: NC
2014 W204 C250
When you say no crank, do you hear the relay click when you try to start the vehicle or no relay click at all?
If you have access to a scanner that can tell you everything is clear to start the car like the immo stuff would be helpful as well.
Do you know if you can still access the modules on the CAN busses when the car won't crank? Based on the codes you provided, you have access to scan more than just the OBD codes.
Basically trying to figure out if it's a CAN issue, an immo issue, a wiring issue or a relay...
If you have access to a scanner that can tell you everything is clear to start the car like the immo stuff would be helpful as well.
Do you know if you can still access the modules on the CAN busses when the car won't crank? Based on the codes you provided, you have access to scan more than just the OBD codes.
Basically trying to figure out if it's a CAN issue, an immo issue, a wiring issue or a relay...
Thread Starter
Junior Member
Joined: Jan 2024
Posts: 27
Likes: 7
C300
I did not have the Scanner when the no crank condtion was present. When trying to crank, you could hear some relays, but pretty similar to when the battery is low. Which made me think that my battery was bad.
When checked later on, in my garage, everything was ok, but was not able to replicate or see the issue again. I cannot see CAN traffic with my scanner, but I can send diag requests, see DTC or live data. I tried to replicate the date to check the Inmo data. I think is ok, since the IPC illuminated when I tried to start it. But again, I was not able to see the inmo request/values when it was not starting.
When checked later on, in my garage, everything was ok, but was not able to replicate or see the issue again. I cannot see CAN traffic with my scanner, but I can send diag requests, see DTC or live data. I tried to replicate the date to check the Inmo data. I think is ok, since the IPC illuminated when I tried to start it. But again, I was not able to see the inmo request/values when it was not starting.
Junior Member
Joined: Feb 2025
Posts: 18
Likes: 4
From: NC
2014 W204 C250
We don't necessarily care about the CAN messages, just that the buses are electrically ok, not shorted to ground and the resistance is correct, there are two, one high speed and one low speed CAN bus.
Having said that I am not convinced it's the CAN bus if relays are clicking when you turn the key/press that start button.
I am concerned about the codes from the Front SAM, the relay could be going bad, the contacts inside arc overtime and degrade to the point where they barely make contact or the resistance is too much for the starter solenoid, not sure that is the case with you but that's how they go out.
Are you able to check the relay in the error code or that's why you need the schematics?
Having said that I am not convinced it's the CAN bus if relays are clicking when you turn the key/press that start button.
I am concerned about the codes from the Front SAM, the relay could be going bad, the contacts inside arc overtime and degrade to the point where they barely make contact or the resistance is too much for the starter solenoid, not sure that is the case with you but that's how they go out.
Are you able to check the relay in the error code or that's why you need the schematics?
Junior Member
Joined: Feb 2025
Posts: 18
Likes: 4
From: NC
2014 W204 C250
After searching for a while, I found this bulletin from Mercedes same symptoms as you, they say it's a faulty relay.
https://lmvindmercedes.com/GetImage.asp?IM=2739
https://lmvindmercedes.com/GetImage.asp?IM=2739
Thread Starter
Junior Member
Joined: Jan 2024
Posts: 27
Likes: 7
C300
Thank you
This is really helpful.
I remove the Relay J, and check it, looked okish (for a potentially 15 year old relay) one terminal in the output had some traces of green patina, so I cleaned it and put it back after test it a handful of times. I order a new one in case it happend again.But after the bulleting, I might be going to the right path.
I wanted to see the schematics to see where the relay control circuits are comming from. check for shorts and sort.... in case the issue still happening. Have you seen a decent set? I stumble uppong a couple of sites, and an ebay seller. But the first couple of sites you paid for them like in a membership type thin.
Thanks again
This is really helpful.
I remove the Relay J, and check it, looked okish (for a potentially 15 year old relay) one terminal in the output had some traces of green patina, so I cleaned it and put it back after test it a handful of times. I order a new one in case it happend again.But after the bulleting, I might be going to the right path.
I wanted to see the schematics to see where the relay control circuits are comming from. check for shorts and sort.... in case the issue still happening. Have you seen a decent set? I stumble uppong a couple of sites, and an ebay seller. But the first couple of sites you paid for them like in a membership type thin.
Thanks again
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