HELP! 2019 C43 Engine not starting but radiator fan turns on at high speed
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HELP! 2019 C43 Engine not starting but radiator fan turns on at high speed
Hi There,
I have a 2019 c43 4 door and drove it earlier today then after several hours in the garage the car won't start but the engine fan (radiator fan) turns on....everything inside the car turns on as well except for the engine?
Would anyone know what the issue is and how i can fix this issue?
Thanks
Mercc43!
I have a 2019 c43 4 door and drove it earlier today then after several hours in the garage the car won't start but the engine fan (radiator fan) turns on....everything inside the car turns on as well except for the engine?
Would anyone know what the issue is and how i can fix this issue?
Thanks
Mercc43!
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From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
.... SOUNDS LIKE SWAMPED
Hi There,
I have a 2019 c43 4 door and drove it earlier today then after several hours in the garage the car won't start but the engine fan (radiator fan) turns on....everything inside the car turns on as well except for the engine?
Would anyone know what the issue is and how i can fix this issue?
Thanks
Mercc43!
I have a 2019 c43 4 door and drove it earlier today then after several hours in the garage the car won't start but the engine fan (radiator fan) turns on....everything inside the car turns on as well except for the engine?
Would anyone know what the issue is and how i can fix this issue?
Thanks
Mercc43!
Connect a $120 MB scanner to read live faults.
The full speed fan means it's not getting any ECU signal.
So something not connected there.
Any heavy rain lately?
Suspects are F-SAM getting rain damaged more so than toasted ECU. See live scan report.
Disconnect batteries before they have a chance to get drained flat by sleepless chassis.
MBWorld God!
Joined: Dec 2019
Posts: 32,375
Likes: 6,326
Hi There,
I have a 2019 c43 4 door and drove it earlier today then after several hours in the garage the car won't start but the engine fan (radiator fan) turns on....everything inside the car turns on as well except for the engine?
Would anyone know what the issue is and how i can fix this issue?
Thanks
Mercc43!
I have a 2019 c43 4 door and drove it earlier today then after several hours in the garage the car won't start but the engine fan (radiator fan) turns on....everything inside the car turns on as well except for the engine?
Would anyone know what the issue is and how i can fix this issue?
Thanks
Mercc43!
you dont need to replace every priceless parts before troubleshooting what's wrong.
Connect a $120 MB scanner to read live faults.
The full speed fan means it's not getting any ECU signal.
So something not connected there.
Any heavy rain lately?
Suspects are F-SAM getting rain damaged more so than toasted ECU. See live scan report.
Disconnect batteries before they have a chance to get drained flat by sleepless chassis.
Connect a $120 MB scanner to read live faults.
The full speed fan means it's not getting any ECU signal.
So something not connected there.
Any heavy rain lately?
Suspects are F-SAM getting rain damaged more so than toasted ECU. See live scan report.
Disconnect batteries before they have a chance to get drained flat by sleepless chassis.
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W212 MY'14 M276-3.5NA @75kMi
I seen some MBs like to run the fan high after reconnecting battery it is not uncommon, but interesting idea on the no ECU signal, I guess similar to how a PC runs the fan high when something is broken and there will be no display, I think it was if there is no memory stick inserted?
It needs an active signal to stay off -
Without an active signal the fan is designed to run and cools high temps...
Last edited by CaliBenzDriver; Jun 29, 2025 at 01:56 AM.
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no rain that day had driven the car prior it only happened to be 40 mins apart the issue started....
checked the fuses again and they seem to be okay. The battery was replaced back in Nov 2024 so i highly doubt it is the issue with the battery
still can't isolate the issue.
Used an OBD2 reader Home Page - Repairsolutions2 and can't get any read back
any other suggestions?
checked the fuses again and they seem to be okay. The battery was replaced back in Nov 2024 so i highly doubt it is the issue with the battery
still can't isolate the issue.
Used an OBD2 reader Home Page - Repairsolutions2 and can't get any read back
any other suggestions?
Out Of Control!!
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From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
GOOD HANDHELD SCANNER
Launch cReader elite MB
Some of us enjoy using this handheld touch screen scanner or better...
Last edited by CaliBenzDriver; Jun 30, 2025 at 12:42 AM.
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thanks calibenz can you send me the exact model number and or link to Amazon I searched by the name and there are ones like this but don’t specify for Mercedes?
[img alt="I see this one but it’s specifies for Honda and Acura
"]https://cimg1.ibsrv.net/gimg/www.mbworld.org-vbulletin/1080x2000/img_0460_03190131e81161645ad5bc94cfe18b991abfa022. jpeg[/img]
I see this one but it’s specifies for Honda and Acura
Last edited by MercC43-2019; Jun 30, 2025 at 06:28 AM.
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update: So ruled out the battery as the i exchanged the one i originally bought in March this year 2025. I bought the Launch Creader Elite for MB today and will come this Wednesday.
When i reconnect the battery the cooling fan turns on at high speed, for about 3 mins or so....and then the fan starts change to a slower speed and then shuts off after a minute (this is when i lock my car) . Once i unlock the car the fan goes back high speed and slows down but i try to start the engine and no luck the car wont start still.
Not sure why this is still doing this...i guess when i get the Launch Creader in hopefully it can isolate why my car won't start and goes through a cooling fan cycle
Will keep posting my updates.. If anyone has any suggestions till i get the launch let me know
Thanks for reading
When i reconnect the battery the cooling fan turns on at high speed, for about 3 mins or so....and then the fan starts change to a slower speed and then shuts off after a minute (this is when i lock my car) . Once i unlock the car the fan goes back high speed and slows down but i try to start the engine and no luck the car wont start still.
Not sure why this is still doing this...i guess when i get the Launch Creader in hopefully it can isolate why my car won't start and goes through a cooling fan cycle
Will keep posting my updates.. If anyone has any suggestions till i get the launch let me know
Thanks for reading
Out Of Control!!
Joined: Apr 2019
Posts: 11,958
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From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
CRAZY FAN... ECU!
update: So ruled out the battery as the i exchanged the one i originally bought in March this year 2025. I bought the Launch Creader Elite for MB today and will come this Wednesday.
When i reconnect the battery the cooling fan turns on at high speed, for about 3 mins or so....and then the fan starts change to a slower speed and then shuts off after a minute (this is when i lock my car) . Once i unlock the car the fan goes back high speed and slows down but i try to start the engine and no luck the car wont start still.
Not sure why this is still doing this...i guess when i get the Launch Creader in hopefully it can isolate why my car won't start and goes through a cooling fan cycle
Will keep posting my updates.. If anyone has any suggestions till i get the launch let me know
Thanks for reading
When i reconnect the battery the cooling fan turns on at high speed, for about 3 mins or so....and then the fan starts change to a slower speed and then shuts off after a minute (this is when i lock my car) . Once i unlock the car the fan goes back high speed and slows down but i try to start the engine and no luck the car wont start still.
Not sure why this is still doing this...i guess when i get the Launch Creader in hopefully it can isolate why my car won't start and goes through a cooling fan cycle
Will keep posting my updates.. If anyone has any suggestions till i get the launch let me know
Thanks for reading
Crazy Fan activity says your ECU has issues... it can be a fuse but that's hardly ever a 5¢ fix.
It's not a failed A/C sensor because engine would still start regardless of high fan.
Believe it or not... this condition is fairly unusual.
It maybe a matured relay keeping part of the ECU OFF or a hungry rat job. We'll see what clues Launch provide us.
Last edited by CaliBenzDriver; Jun 30, 2025 at 03:36 PM.
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update: So ruled out the battery as the i exchanged the one i originally bought in March this year 2025. I bought the Launch Creader Elite for MB today and will come this Wednesday.
When i reconnect the battery the cooling fan turns on at high speed, for about 3 mins or so....and then the fan starts change to a slower speed and then shuts off after a minute (this is when i lock my car) . Once i unlock the car the fan goes back high speed and slows down but i try to start the engine and no luck the car wont start still.
Not sure why this is still doing this...i guess when i get the Launch Creader in hopefully it can isolate why my car won't start and goes through a cooling fan cycle
Will keep posting my updates.. If anyone has any suggestions till i get the launch let me know
Thanks for reading
When i reconnect the battery the cooling fan turns on at high speed, for about 3 mins or so....and then the fan starts change to a slower speed and then shuts off after a minute (this is when i lock my car) . Once i unlock the car the fan goes back high speed and slows down but i try to start the engine and no luck the car wont start still.
Not sure why this is still doing this...i guess when i get the Launch Creader in hopefully it can isolate why my car won't start and goes through a cooling fan cycle
Will keep posting my updates.. If anyone has any suggestions till i get the launch let me know
Thanks for reading
In the meantime, with the help of other forum members here, will join in to try to help to the best of my knowledge.
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Hi CaliBENZ,
Yup i have a battery tender to keep the battery from dying...i've un-plugged the car completely off from the battery and have the tender going.
As for the fuse i've checked the fuses physically and also using a multi-meter to make sure there wasn't a break on all fuse boxes. ...no dice and everything checks out. But out of curiousity where would the ECU located in which slot in the Engine compartment fuse box? i've looked at the fuse allocation sheet that the provides in the back of the trunk and i clearly doesn't label a ECU fuse location. Maybe it's "Engine Electronics" fuses - 101 to 104, 113,118,119, 125, 127,(301,315,335 - located in the passenger fusebox)?
I can physically check for the ac sensor however where would that be located?
I'm still waiting on the 2025 Launch Creader Elite V2.0 to come in tomorrow (standby...) Amazon.com: 2025 LAUNCH Creader Elite V2.0 fit for Mercedes-Benz MB Sprinter Maybach Bi-Directional Scan Tool, OBD2 Scanner, Full System Diagnostic, All Reset Service, ECU Coding, Auto Vin, Lifetime F-Ree Update : Automotive
thanks for keeping in touch and suggesting
Yup i have a battery tender to keep the battery from dying...i've un-plugged the car completely off from the battery and have the tender going.
As for the fuse i've checked the fuses physically and also using a multi-meter to make sure there wasn't a break on all fuse boxes. ...no dice and everything checks out. But out of curiousity where would the ECU located in which slot in the Engine compartment fuse box? i've looked at the fuse allocation sheet that the provides in the back of the trunk and i clearly doesn't label a ECU fuse location. Maybe it's "Engine Electronics" fuses - 101 to 104, 113,118,119, 125, 127,(301,315,335 - located in the passenger fusebox)?
I can physically check for the ac sensor however where would that be located?
I'm still waiting on the 2025 Launch Creader Elite V2.0 to come in tomorrow (standby...) Amazon.com: 2025 LAUNCH Creader Elite V2.0 fit for Mercedes-Benz MB Sprinter Maybach Bi-Directional Scan Tool, OBD2 Scanner, Full System Diagnostic, All Reset Service, ECU Coding, Auto Vin, Lifetime F-Ree Update : Automotive
thanks for keeping in touch and suggesting
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yup i did get the V2.0, If you're in the Toronto area or GTA let me know i can send you my contact via DM
Thread Starter
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forgot to mention in my last post, the car generally is a house garage where no critters can get it unless i leave the garage door open overnight, but i'll double check to see if any critters have decide to feast on a few wires.
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UPDATE: i just got my scanner yesterday and of course a whack of Ucodes came through - it is suspected that the car is not communicating with a no crank. The fan does turn on initially in high speeds anytime i unlock the car, open the door etc. (but still no start)
Somewhere maybe on of the modules isn't communicating, i've checked all the fuses they seem to be okay, and prefuse box (Engine bay) as well to see if there was a break in the fuse (no dice)....i'm running out of options and it almost looks like i'll have to take it in the MB dealership :S (ugh...not ideal)
any help or suggestions to help trouble shoot the unknown issue i am having....
Somewhere maybe on of the modules isn't communicating, i've checked all the fuses they seem to be okay, and prefuse box (Engine bay) as well to see if there was a break in the fuse (no dice)....i'm running out of options and it almost looks like i'll have to take it in the MB dealership :S (ugh...not ideal)
any help or suggestions to help trouble shoot the unknown issue i am having....
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From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
UPDATE: i just got my scanner yesterday and of course a whack of Ucodes came through - it is suspected that the car is not communicating with a no crank. The fan does turn on initially in high speeds anytime i unlock the car, open the door etc. (but still no start)
Somewhere maybe on of the modules isn't communicating, i've checked all the fuses they seem to be okay, and prefuse box (Engine bay) as well to see if there was a break in the fuse (no dice)....i'm running out of options and it almost looks like i'll have to take it in the MB dealership :S (ugh...not ideal)
any help or suggestions to help trouble shoot the unknown issue i am having....
Somewhere maybe on of the modules isn't communicating, i've checked all the fuses they seem to be okay, and prefuse box (Engine bay) as well to see if there was a break in the fuse (no dice)....i'm running out of options and it almost looks like i'll have to take it in the MB dealership :S (ugh...not ideal)
any help or suggestions to help trouble shoot the unknown issue i am having....
If its dead as door nail then its SAM-CGW, but that's working because it still managing chassis power (fan gies to sleep!)
Mercedes plug (OBD DLC) runs off CAN-D a special diagnostic network path.
What does the SCANNER SCREEN SHOWS ???
Do you go through VIN selection then what?
Try using manual VIN selection.
Last edited by CaliBenzDriver; Jul 4, 2025 at 03:30 PM.
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2015 C400 4MATIC Palladium Silver Metallic
YIKES!
Have you checked your cam magnet and cam position sensor harnesses for oil ingress?
Tried disconnecting the ECU and cleaning the connector with electric contact cleaner?
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W212 MY'14 M276-3.5NA @75kMi
CAN-C IS DOWN
What a comprehensive report. It shows us the whole reality of your car.
> Report: good + bad:
-- Super useful to see that ECU + TCU + ISM are MIA: kaput !!
-- ESP is still "responding" to scan but has the use of multiple networks to talk...
The bottom line is : you have a real CAN-C issue, it impacts more than ECU alone.
> CAUSE:
-- What's forcing CAN-C to stay down is the question.
This can be simple with no expensive blind-shots.
-- Right now the WHOLE CAN-C string of modules is missing.... as in it must be shorted. How do these chassis routinely deliver that (swamped) ?
-- I do NOT think power supply is missing from F-SAM.
> TROUBLESHOOTING:
Disconnect your non-stop fan to preserve battery power while engine is off (Do reconnect it with engine running...)
-- 1 > Disconnect ECU out of circuit.
Rescan without ECU connected.
Are TCU + ISM alive now ??
-- 2 > Go look at your CAN BUS-BARS for water crusties signs.
Carpeting at front doors thresholds on both sides.
Be sure to carefully tag each individual wire position then disconnect them until bus comes back alive, hopefully. (each has an individual slot that identify what connector it is - Not random.)
At that point you should know what single module is collapsing your CAN-C Bus.
> Report: good + bad:
-- Super useful to see that ECU + TCU + ISM are MIA: kaput !!
-- ESP is still "responding" to scan but has the use of multiple networks to talk...
The bottom line is : you have a real CAN-C issue, it impacts more than ECU alone.
> CAUSE:
-- What's forcing CAN-C to stay down is the question.
This can be simple with no expensive blind-shots.
-- Right now the WHOLE CAN-C string of modules is missing.... as in it must be shorted. How do these chassis routinely deliver that (swamped) ?
-- I do NOT think power supply is missing from F-SAM.
> TROUBLESHOOTING:
Disconnect your non-stop fan to preserve battery power while engine is off (Do reconnect it with engine running...)
-- 1 > Disconnect ECU out of circuit.
Rescan without ECU connected.
Are TCU + ISM alive now ??
-- 2 > Go look at your CAN BUS-BARS for water crusties signs.
Carpeting at front doors thresholds on both sides.
Be sure to carefully tag each individual wire position then disconnect them until bus comes back alive, hopefully. (each has an individual slot that identify what connector it is - Not random.)
At that point you should know what single module is collapsing your CAN-C Bus.
Last edited by CaliBenzDriver; Jul 5, 2025 at 04:31 PM.
