W221 S350 Bluetech 2011 Intermittent non-start issue

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ksebs

New Member
Joined
Dec 27, 2023
Messages
7
Location
London
Car
W221 S350 Bluetech
Dear All,

I have bee living with a painful issue with my car for 3 years now, and managed to make some observations which might help some expert to provide a guess on what could be causing this? In a nutshell, sometimes the car doesn't start, doesn't even crank when turning to key completely to the right.

Car: S350 Bluetech, 2011 (W221)

Sidenote: when the car turns on ok (and it always does eventually, but sometimes after an hour, sometimes after second try), all errors disappear, and drives smoothly as it should.

Symptoms:
-Ignition key turned to second position (just before turning the engine on), turning further wouldn't turn the engine on, not even a crank comes out.
-On the dash 2 errors come up: Run flat inoperative, ESP Inoperative
-The engine cooler temperature doesnt move at all on the dash (even if the car has been running before and I am 100% sure it would be over 60-80C
-The little coil sign (pre-ignition glow thingy) doesn't show up at all on the dash, even if the engine is completely cold
-I can't hear the hissing sound of the compressor (for air suspension) so pretty sure that doesn't turn on either
=Reading errors out, 2 peding one shows up: P0113 - Intake Air Temperature Sensor 1, P00AD Intake Air Temperature Sensor 1

I also figured that it has to do something with the battery voltage, as:
- It always happens during winter and cold periods. I don't think I have seen it in summer
- It very rarely occurs after the car has been previously running and warm. Note that voltage is always higher after an extended run (battery more charged)
- When my battery was depleted (below 12V), it took me an hour to start the car, turning the key back and forth, praying, etc. When I changed to a fully charged battery, the error may come up, but I can turn the engine on after trying for 2-3 times
- I once also tried to jack the car up from a running car after 20 minutes of failure to start it on its own, the car instantly started, error was not showing up at all

Now the issue is that even with a brand new, fully charged 95Ah AGM battery, I do get this error and intermittent non-start issue.

Also to note:
-When the key is turned to position 2, a lot of consumers are turned on. Air suspension compressor would start, pre-ignition glow, aircon air, etc. I can see that the battery at this point (even before trying to crank the engine on) drops about 0.5volts. Fully charge brand new battery installed shows only 12.5V, and once I turn the key twice, that 12.5 drops to 12.0
-It has happened a few times that I turn key to position 2, I do see the glow plug show up for a half sec/air suspension starting to hiss, than suddenlly these cut off, the error message appears on the dash and I can be sure that I won't be able to turn the car on at that point.

So could this be a short-circuit or something like that caused by something that's turned on at ignition position 2? And voltage drops, some module malfunctions and hence errors show up/car doesnt start? What is really weird that the car eventually always turns on - just sometimes may take an hour, or locking doors after an unsuccesful try and retrying it 20 minutes later.

Really appreciate even guesses.
 
Well could be a ignition barrel that is faulty,but the glow plug light might well be a fuse check all the fuses .
 
Dear All,

I have bee living with a painful issue with my car for 3 years now, and managed to make some observations which might help some expert to provide a guess on what could be causing this? In a nutshell, sometimes the car doesn't start, doesn't even crank when turning to key completely to the right.

Car: S350 Bluetech, 2011 (W221)

Sidenote: when the car turns on ok (and it always does eventually, but sometimes after an hour, sometimes after second try), all errors disappear, and drives smoothly as it should.

Symptoms:
-Ignition key turned to second position (just before turning the engine on), turning further wouldn't turn the engine on, not even a crank comes out.
-On the dash 2 errors come up: Run flat inoperative, ESP Inoperative
-The engine cooler temperature doesnt move at all on the dash (even if the car has been running before and I am 100% sure it would be over 60-80C
-The little coil sign (pre-ignition glow thingy) doesn't show up at all on the dash, even if the engine is completely cold
-I can't hear the hissing sound of the compressor (for air suspension) so pretty sure that doesn't turn on either
=Reading errors out, 2 peding one shows up: P0113 - Intake Air Temperature Sensor 1, P00AD Intake Air Temperature Sensor 1

I also figured that it has to do something with the battery voltage, as:
- It always happens during winter and cold periods. I don't think I have seen it in summer
- It very rarely occurs after the car has been previously running and warm. Note that voltage is always higher after an extended run (battery more charged)
- When my battery was depleted (below 12V), it took me an hour to start the car, turning the key back and forth, praying, etc. When I changed to a fully charged battery, the error may come up, but I can turn the engine on after trying for 2-3 times
- I once also tried to jack the car up from a running car after 20 minutes of failure to start it on its own, the car instantly started, error was not showing up at all

Now the issue is that even with a brand new, fully charged 95Ah AGM battery, I do get this error and intermittent non-start issue.

Also to note:
-When the key is turned to position 2, a lot of consumers are turned on. Air suspension compressor would start, pre-ignition glow, aircon air, etc. I can see that the battery at this point (even before trying to crank the engine on) drops about 0.5volts. Fully charge brand new battery installed shows only 12.5V, and once I turn the key twice, that 12.5 drops to 12.0
-It has happened a few times that I turn key to position 2, I do see the glow plug show up for a half sec/air suspension starting to hiss, than suddenlly these cut off, the error message appears on the dash and I can be sure that I won't be able to turn the car on at that point.

So could this be a short-circuit or something like that caused by something that's turned on at ignition position 2? And voltage drops, some module malfunctions and hence errors show up/car doesnt start? What is really weird that the car eventually always turns on - just sometimes may take an hour, or locking doors after an unsuccesful try and retrying it 20 minutes later.

Really appreciate even guesses.
Damaged ECU caused by water? If drains blocked at windscreen base, water overflows into battery compartment and could damage the ECU located nearby
 
Well could be a ignition barrel that is faulty,but the glow plug light might well be a fuse check all the fuses .
Thanks for the quick reply! Is it easy to test if the ignition barrel is causing this?
 
Damaged ECU caused by water? If drains blocked at windscreen base, water overflows into battery compartment and could damage the ECU located nearby
Thank you, that could well be the problem - drains were indeed blocked a while ago. And in fact this error also came up at least twice with a warm engine (which it would rarely do) when car was exposed to water - once straight after I washed the car with jetwash, and once after a long drive in the rain.

Pretty annoying that none of the garages (even MB ones) check/clean the drains, it took me a while to realise that I have to do this myself.

Would higher voltage still help to start the car and make the errors go away, if it is indeed the ECU that is damaged? Just this morning, tried to turn on the car and usual errors came up. Then I jacked the car up with another battery (a 3yr old genuine MB I just recently swapped out for the brand new), and all errors disappeared and car started straight away.

Also, is my battery voltage normal? Brand new battery (95Ah AGM Varta, slightly bigger capacity than what MB had there originally), fully charged - was 12.7V installed. Drove 3 hours on highway, next morning battery voltage only showing 12.2-12.3V. And if I turn key twice, when all consumers start (air compression, pre-ignition glow thing), voltage drops 0.5V to below 12V, and that's just before I get to cranking up the engine.

Any recommendations for a good independent garage in London highly appreciated!
 
What voltage do you have on the battery when engine running, should be around 14v, if not then battery not being charged.
 
Goes up to 14.7-14.8V while the engine is running
 
Would not expect to see a voltage drop on a new battery the next morning after a 3 hour run. Maybe might be worth checking for a parasite current draw using an amp meter (be careful if you do) cars take a while to shut down fully, would expect to see no more than 30mA or so draw when fully shut down.
 
Would not expect to see a voltage drop on a new battery the next morning after a 3 hour run. Maybe might be worth checking for a parasite current draw using an amp meter (be careful if you do) cars take a while to shut down fully, would expect to see no more than 30mA or so draw when fully shut down.
DO you know if Ksebs fixed his Problem with his S Class Please Sir. Mine is the same year same car same problem .Thanks
 
DO you know if Ksebs fixed his Problem with his S Class Please Sir. Mine is the same year same car same problem .Thanks
Hey, yes I have. Have a look at this thread, find my replies there - i put in some screenshots and links to the relay that you need to order:

Basically it's a corroded relay which you can order from ebay from max £10 and change it yourself (4 screws to pull out Engine control unit, then about 3 to access the SAM modul in which you can find the relays that you can pull out/change by hand, about 10 mins job). But if you bring it to a garage/dealership, they will have no clue, and may try guessing and will suggest changing ECU for £1000, EIS and lots of expensive parts.
 
Hey, yes I have. Have a look at this thread, find my replies there - i put in some screenshots and links to the relay that you need to order:

Basically it's a corroded relay which you can order from ebay from max £10 and change it yourself (4 screws to pull out Engine control unit, then about 3 to access the SAM modul in which you can find the relays that you can pull out/change by hand, about 10 mins job). But if you bring it to a garage/dealership, they will have no clue, and may try guessing and will suggest changing ECU for £1000, EIS and lots of expensive parts.
Was it the Terminal 87 relay ?
 
Hey, yes I have. Have a look at this thread, find my replies there - i put in some screenshots and links to the relay that you need to order:

Basically it's a corroded relay which you can order from ebay from max £10 and change it yourself (4 screws to pull out Engine control unit, then about 3 to access the SAM modul in which you can find the relays that you can pull out/change by hand, about 10 mins job). But if you bring it to a garage/dealership, they will have no clue, and may try guessing and will suggest changing ECU for £1000, EIS and lots of expensive parts.
Its a pity this isn't "Must read" info for Merc Tech Staff everywhere. I read your thread yesterday and admire your tenacity .I'm ready for the Motorway Bridge Flyers Association now, after 12 months . Thanks for you help mate
 
Its a pity this isn't "Must read" info for Merc Tech Staff everywhere. I read your thread yesterday and admire your tenacity .I'm ready for the Motorway Bridge Flyers Association now, after 12 months . Thanks for you help mate
Unfortunately Mercedes like most large corporations simply do not care about bad publicity. It will likrly6have no effect on anyone considering buying a car from them.
 
Was it the Terminal 87 relay ?
Yes, and pretty easy to test if this is your issue - pull out the relay without replacing, try to start the car, and it will produce the same exact symptoms.
And mine was pretty green corroded on the leg once I pulled out, which further confirmed that it's the faulty one.
 
Its a pity this isn't "Must read" info for Merc Tech Staff everywhere. I read your thread yesterday and admire your tenacity .I'm ready for the Motorway Bridge Flyers Association now, after 12 months . Thanks for you help mate
The other thread was started by another guy with the same issue - I was really lucky that he went back to the same garage several times until they found the issue. They did change a lot of things for him though, although I think he also had real other, unrelated problems (wheel sensors, whole on the car bottom that let some water in, etc)
 

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