W211 E320 cdi - Serious Electrical Problems

[golf2]

Hi guys,

I've got an electrical fault on my 2003 E320 cdi which is intermittent and I need to get it sorted ASAP.

This fault has been present for several years now and it has been looked at by Mercedes several times before.

The symptoms of the fault are usually a warning light in the instrument cluster coming on saying instrument cluster fault, visit workshop, followed by the air con and fans switching themselves on and off and the stereo switching itself on and off repeatedly every 10 seconds or so. I also get SRS malfunction come up on the instrument cluster sometimes whilst this is happening.

It may be a coincidence, but it would seem like what usually triggers this fault is when I use left left hand indicator. I will be driving the car, go to indicate left and then the electrical fault appears with the symptoms I described above and the only way to stop the fault is to pull over, remove the key from the ignition and wait 5 minutes or so for all the electrical systems to switch off. When I restart the car, everything is perfect again. This happens randomly, I could go several weeks or just days between when the fault occurs.

I am starting to wonder if it's a water related problem because it does seem to happen more often after I've washed the car or after it's rained the night before etc.

When Mercedes looked at it, they initially couldn't find anything wrong with it but eventually they thought it had a faulty battery voltage regulator which was replaced but the fault came back again shortly after. I was then advised that the alternator could be faulty so this was replaced and the fault is still present.
I then replaced both the main engine battery and the auxiliary battery with brand new ones as the old ones were over 6 years old but the fault is still there!

I have checked for damp in the foot wells and it all feels bone dry to me, I've checked the drains in the scuttle area and they are all clear and water is draining freely down the pipe which enters the passenger side wing.

Does anyone have any suggestions of what I could check please? I'm very keen to get this fixed as it's making me nervous about driving the car. I do have a iCarsoft i980 code scanner and after clearing all the codes and then checking the codes after the fault has happened there's loads of fault codes appeared. I'll make a list below if some of the codes:

Airbag - 9076 CAN communication is faulty

Overhead Control Panel - 90E8 CAN communication with control unit DCM-FR is sporadically disturbed

Upper Control Panel - 9027 CAN communication is faulty

Driver side SAM - 9090 Fault in CAN communication with control unit OCP

Passenger side SAM - 9091 Control unit N73 (EIS [EZS] control unit) is not transmitting data on the CAN bus

Rear SAM - 9044 Control unit N82 (Battery control module) is not transmitting data on the CAN bus

Instrument Cluster - 9101 Fault in CAN communication with control unit ESP Electronic Stability Program

Steering Column Module - 9005 Fault in communication on interior CAN databus

Door Control Module Front Left and Right - 9010 N69/1 The supply voltage is too low

Door Control Module Rear Left and Right - 9010 N69/1 The supply voltage is too low

Convenience Auto Air Conditioning - 9600 CAN bus off

All of these codes have appeared when the fault occurs, none of them were there before and they all come back every time the fault occurs.

If anyone has any ideas of what I should try it would be really appreciated! Thanks in advance.

Tom

 

[Dec]

If the use of the indicators triggers the fault, will the use of the hazards also trigger the fault?

Dec

 

[OscarOzze]

ECU?


Sent from my iPhone using Tapatalk

 

[golf2]

If the use of the indicators triggers the fault, will the use of the hazards also trigger the fault?

Dec

I will try this out but it only happens randomly so I'll give it a go and get back to you. Thanks for the replies!

 

[golf2]

I haven't managed to replicate the fault yet but I will keep trying!

 

[Dec]

Is your car alarm 14 years old and does it work properly if you intentionally trigger it?

Dec

 

[golf2]

Is your car alarm 14 years old and does it work properly if you intentionally trigger it?

Dec

Yes the alarm is the original factory fitted one. I will give that a test, stupid question but how would be best to deliberately trigger it?

Thanks in advance.

Tom

 

[Dec]

-Open the drivers window/any window.
-Lock car with remote.
-Wait 60 seconds for alarm to arm, I think a light should be blinking on dash when alarm armed.
-Reach in the open window and open a door and pop bonnet for good measure.
-The alarm siren should sound for 30 seconds and the hazards should flash for 3 minutes.

Time the above for the full 3 minutes.
If you put the key into the ignition or unlock the car with the remote, before the 3 minute test is up, then the alarm will be disarmed.

Dec

 

[golf2]

-Open the drivers window/any window.
-Lock car with remote.
-Wait 60 seconds for alarm to arm, I think a light should be blinking on dash when alarm armed.
-Reach in the open window and open a door and pop bonnet for good measure.
-The alarm siren should sound for 30 seconds and the hazards should flash for 3 minutes.

Time the above for the full 3 minutes.
If you put the key into the ignition or unlock the car with the remote, before the 3 minute test is up, then the alarm will be disarmed.

Dec

Thanks Dec, I will give this a go today and let you know the outcome.

 

[golf2]

-Open the drivers window/any window.
-Lock car with remote.
-Wait 60 seconds for alarm to arm, I think a light should be blinking on dash when alarm armed.
-Reach in the open window and open a door and pop bonnet for good measure.
-The alarm siren should sound for 30 seconds and the hazards should flash for 3 minutes.

Time the above for the full 3 minutes.
If you put the key into the ignition or unlock the car with the remote, before the 3 minute test is up, then the alarm will be disarmed.

Dec

Right I've finally been able to test this and the alarm seems to be working fine. The only thing I did notice is that the little motion detector which flips down from the rear dome light is getting jammed or sometimes stuck in the down position. It looks like there's a little motor and a plastic cog which opens and closes the sensor and I think that's broken.

I've actually had the electrical fault another 2 times since I last posted and both times it happened without me using the indicators. I was just driving steadily on the motorway and I suddenly got the display faulty message and the radio and fan blowers switching on and off repeatedly followed by the SRS system fault message and indicators not working or a delay before working.

I had to pull over and take the key out and let everything completely switch off again which resets it. It was fine again after that.

Very strange!!

 

[Dec]

It could be expensive to track down an intermittent fault like that, if hooking up to diagnostics can’t pinpoint the fault then you may have to throw parts at the problem too.

Supposing you stopped using things you don’t need, like the alarm and stopped using the central locking by instead locking the car with only the mechanical key blade, you would also need to disable the automatic central locking system… doors lock when car reach 10mph.

You could also disable the radio/stereo by removing fuses and do without the blower/heating system by removing its fuse.
Maybe disabling what you don’t need, for a while, to see if the fault reappears.

Dec

 

[golf2]

It could be expensive to track down an intermittent fault like that, if hooking up to diagnostics can’t pinpoint the fault then you may have to throw parts at the problem too.

Supposing you stopped using things you don’t need, like the alarm and stopped using the central locking by instead locking the car with only the mechanical key blade, you would also need to disable the automatic central locking system… doors lock when car reach 10mph.

You could also disable the radio/stereo by removing fuses and do without the blower/heating system by removing its fuse.
Maybe disabling what you don’t need, for a while, to see if the fault reappears.

Dec

Thanks Dec, that sounds like a good idea. I'm going to remove the COMAND unit today and check for any squashed or exposed wiring as I read on another forum this had happened to someone and they had very similar problems.

I also have a voltage logger which I will connect to the wiring somewhere behind the dash or cigarette lighter and check if there are any fluctuations in voltage which is triggering the strange behavior. I will leave that connected until the fault reappears.

It's going to be a slow process but will get there in the end!

Tom

 

[golf2]

Just out of curiosity, is the alarm system a common problem on these?

 

[Dec]

The alarm system is a common problem on all MB’s as the age, the Mercedes alarm system brain is contained within the alarm siren and is powered by rechargeable 7.2v batteries. Removing the alarm fuse doesn’t kill the alarm as it has its own batteries, but removal of the alarm fuse will stop the siren batteries from charging.

Even if the internal rechargeable batteries are flat, the siren is still connected to the cars electrics, so, the only way to disable it is to unplug it, which will do you for now, or, you could replace it with a new siren for around £100 if you DIY.. easy job to do, see… W211 Alarm Siren replacement - MBClub UK - Bringing together Mercedes Enthusiasts

From about mid? 1997 the same or similar type of siren was used on most MB’s as seen in this image link here… https://www.google.ie/search?q=merc...IMAKHandAFQQ_AUIBigB&biw=1328&bih=863#imgrc=_

After about 10 years, the siren batteries deteriorate and the PCB becomes damaged resulting in false alarms and sometimes odd behaviour. If your
alarm siren is indeed 14 years old then it’s likely not to be in the best of health.

I’m not saying the alarm is the cause of your fault but at 14 years old it’s not to be trusted, not sure if the motion detector fault is an alarm fault or a central locking fault.


Dec

 

[golf2]

Hi guys,

Just to update you on this problem, I replaced the key fob batteries and the problem seemed to disappear for about 4-5 months. I thought the problem was cured but it's now come back again. I have tried changing the key fob batteries again but no luck. I'm assuming it was just pure coincidence that the problem went away for several months, rather than it being the new batteries.

I'm going to have to take the car to a Mercedes specialist now the problem has come back but thought I'd ask again on here just in case anyone has any other ideas?

To add a few more details about the fault, whilst driving the vehicle at any speed I suddenly get a 'Display Faulty' message, followed by 'SRS system defective', followed by a key icon and sometimes a battery icon.
The comand/radio system turns on and off continuously every few seconds and the air con fans turn on and off continuously as well.
The electric windows become intermittent and the indicators/hazard lights become erratic (front only, rears still work fine). Also the dipped beam headlights work fine but if I switch on full beam, they flicker on and off randomly. Also the puddle lighs flicker on and off when the doors are open, and the heated seats stop working completely.

The only way to stop all of the above is to pull over and switch the ignitin off for a couple of minutes until everything is switched off. After that, everything is perfect again for the rest of the journey.

This happens a few times a week and often it happens about 20-30 minutes into a journey.

As above, it's had brand new main battery and aux battery, new alternator and voltage regulator.

When using a code reader I get error codes for just about everything!

I'm starting to think it could be a faulty SAM module or central gateway. I'm just not sure which.

If anyone has any experience with similar faults or any suggestions before I take it to a specialist it would be much appreciated.

My concern is that if I take it to a garage they will start throwing parts at it and it'll cost a fortune. That's what the Mercedes dealership did previously when my father owned the car before he passed away. They couldn't diagnose the fault because it was intermittent, even with the star diagnostics!

 

[pmcgsmurf]

When using a code reader I get error codes for just about everything!

Have you tried clearing all the codes then see what comes back?

 

[golf2]

Yes I did try that initially and after the fault occurred, I got all the codes.

There were codes for lots and lots of things, communication errors and low voltage errors, CAN bus errors etc.

I've actually used a voltage logger on the car to check there aren't any drops or spikes in voltage before or during the fault but it's solid at around 14.2v.

 

[merc85]

Have you check the boot area for damp, Rear sam unit is in the nsr 1/4 along with the audio gateway. It sits above side bumper vent

 

[golf2]

Yes I did remove the boot lining and there were no obvious signs of damp around the rear SAM area that I could see. It all looked clean and dry.

The car was also kept in a garage most of it's life so is generally very clean and no signs of any water ingress or blocked drains.

Thanks.

 

[golf2]

Its strange that when the fault occurs the rear indicators work fine but the front ones don't, and the full beam headlights flicker but dipped beam are fine.

I'm not sure which SAM units control each of those things.

I actually took some video clips of these things happening.