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Hipo64
Hipo64, Mercedes Technician
Category: Mercedes
Satisfied Customers: 3483
Experience:  Work and diagnose electronics on daily basis.
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Desperately hoping you can help us...we have a 2005 ML 500

Customer Question

Customer: desperately hoping you can help us...we have a 2005 ML 500 with some strange recurring and worsening electrical/communication problems...I found you through a google search hit from a thread you posted with a mechanic in Australia two years ago. The vehicle is running/starting/shifting perfectly, battery has been replaced by dealer in the last 6 months but problems are getting worse. Initially the entire instrument cluster would occasionally twitch then all needles would drop to 0
JA: Thanks. Can you give me any more details about your issue?
Customer: initially just the cluster...now the headlights and interior dome lights flash and the nav system is acting really strange....it works but is slow to respond...takes 20 minutes to input a destination and gets stuck...as of today the cd player won't function
JA: OK got it. Last thing — JustAnswer charges a fee (generally around $18) to post your type of question to Mercedes Experts (you only pay if satisfied). There are a couple customers ahead of you. Are you willing to wait a bit?
Customer: absolutely as long as Michael can help me....I specifically found him through this thread and believe my problem may be similar...his specific expertise is of value to me... http://www.justanswer.com/mercedes/7lv6y-sl500-hi-own-workshop-customers-car-here-wdb2304752f114136.html#re.v/446/
JA: OK. Now I'm going to take you to a page to place a secure deposit with JustAnswer. Don't worry, this chat is saved. After that, we will finish helping you.
Submitted: 11 months ago.
Category: Mercedes
Expert:  Pete replied 11 months ago.

My name is ***** ***** I am a professional here at Just Answer. I noticed that your question had not received a response and thought I would see if you still need help with this.I apologize for the delay and I hope I can still assist you with this here.

This sounds like you may have more then one component acting up here.

The cd changer is a common component to fail itself internally requiring replacement when it does fail.I have had to replace several of these before for this issue here.This can also cause the command/nav system to act slow as it is trying to communicate with the cd changer.I have however seen issues with the command/navigation/radio itself as well to where it acts up internally needing replaced.

As for the issues with the cluster and the lights follow and trace the power and ground cables from the battery to see if there are any issues found with the cables themselves or the cable connections.If a fault is found with the cables or connections being damaged,loose or corroded this will have to be corrected to resolve this issue here.If this is all checked and found to be o.k. let me know so we can continue.

If more help is needed, use the reply tab to continue our conversation. If no further assistance is needed, kindly rate my service.You can rate at any time and we can continue to work on your question as this will not close out your question.Keep in mind in some cases it can be difficult to fully diagnose or help repair your vehicle without seeing it and I work on delivering the best possible answer from what I see to work with.

Thanks Pete

Customer: replied 11 months ago.
The car spent 6 hours with a Mercedes tech at the dealership (tracing wires/troubleshooting) and the cluster was sent out previously to be bench tested by our local import mechanic...the cluster problem happened first...intermittently over the past 6 months now almost daily...in the last month lights in the cabin and headlights flash when cluster loses power and the nav has been slow to respond and as of yesterday will not complete a destination input to directions at all and last night on the way home from the dealership the cd changer would not work (it worked on the trip to the dealership)
Expert:  Pete replied 11 months ago.

Has anything after market been wired in or installed at all before the issues started to occur here?

Customer: replied 11 months ago.
absolutely nothing
Expert:  Pete replied 11 months ago.

Unfortunately this is a difficult question for me to answer myself here.

I will open your question up for others here to see if someone else can assist further on this as there may be others here that may have more info on what to check or do with this issue.I hope you can get this resolved with ease.No need to reply to my last post here unless it is a last resort as it will keep your question locked to me and others will not be able to view it.If you feel you want to continue to work with me on this feel free to reply at any time but keep in mind in some cases it can be difficult to fully diagnose or help repair this without seeing your vehicle.

Thanks Pete

Customer: replied 11 months ago.
thank you....we have a bumper to bumper extended warranty with only 700 remaining before expiration...we have had it at our local mechanic and to Mercedes as I mentioned....there is nothing to "see" which seems to be exactly the problem...I see Michael answered a somewhat similar question so we are hoping someone here is familiar with this specific issue....the local mechanic sent out the cluster for bench testing and the problem could not be recreated but when it is reconnected to the car it happens and has gotten more frequent in the past month...I am more than happy to send you a video of the gauges sputtering and dropping to zero as we are driving down the interstate...we provided it to the warranty company which is why they have agreed to fix it...however, the cluster itself does not seem to be the problem since it works fine when NOT connected to the vehicle...local mechanic called it a communication error....Mercedes mechanic just shrugged his shoulders and said we can replace the cluster but has no real confidence this will fix the problem...as the cluster problem worsened the nav began to act strange and, as I mentioned the cd changer now will not function since we left the diagnostic marathon appointment at the dealership....could it be a SAM failure or the AGW?....this is profoundly important because if the problem is not fixed we are done...our warranty is over and we cannot afford the expense of fixing it when we finally experience a catastrophic failure which, with the mounting electrical anomalies seems inevitable....this is our ONLY vehicle for a family of 5....please help
Expert:  Hipo64 replied 11 months ago.

Hi, my name is ***** ***** I would like to help you with your problem, After I have read your description of the problem and examining wiring diagram

I see that only unit that can possibly affect Instrument cluster communication, Navy and instrument power supply is the Extended Activity Module, it is located under dash on the drivers side

if you look under center of drivers side dash you will see black box, I would have this componnent removed and inspected fpr corrosion on the circuit board, I bad module will affect communication to cluster and other modules.

Please have it checked and let me know.

Regards Pavlin!

Customer: replied 11 months ago.
thank you!...will discuss this with the Mercedes tech....he claims there are no error codes indicating failure of any component...is this normal? The warranty company has agreed to replace the instrument cluster but it seems like replacing the AAM makes more sense....how can the problems be isolated to the instrument cluster with now two more unrelated problems, right?....Any suggestions on how to approach this with either the warranty company or the stubborn ; ) tech? Can you give me some guidance on how to frame this with them?
Expert:  Hipo64 replied 11 months ago.

Hi, it is Not AAM I refer to, it is EAM under left side of dash, I would start with removing the module, open it and physically expect circuit board for any sign of corrosion and or oxidation.

Regards Pavlin!

Expert:  Hipo64 replied 11 months ago.

I am sorry, I pressed wrong button on my smart phone, I am not opting out of the question.

Customer: replied 11 months ago.
EAM..got it...is that something we can do? the dealer tech seems to have zero interest in diagnosis which makes it difficult to convince the warranty company : )
Expert:  Hipo64 replied 11 months ago.

Hi, you can remove it and open it for inspection. It is not hard to do. Lets start here, just open it and do visual inspection.

Customer: replied 11 months ago.
will do it tomorrow and let you know!
Expert:  Hipo64 replied 11 months ago.

Happy New Year! Best wishes!

Customer: replied 11 months ago.
there are two boxes under the driver's side and neither seem to be correct and/or accessible...guessing there is confusion on my end since the only one that seems accessible has only two plugs which does not seem to match any schematic/photo/guide I can find...can you give me some more specific guidance on finding and removing the EAM?
Customer: replied 11 months ago.
while waiting for your reply did some investigating and may have found something....may have discovered the problem....rear tail light cracked and standing water inside the light on left (side marker lamp) and right bulb is blown...fuse is not blown...could data faulty data be sent from this short ...could this be causing all the problems?
Expert:  Hipo64 replied 11 months ago.

http://workshop-manuals.com/mercedesbenz/ml_320_(163.154)/v6-3.2l_(112.942)/heating_and_air_conditioning/relays_and_modules_hvac/control_module_hvac/component_information/description_and_operation/all_activity_module_task/page_10141/

Expert:  Hipo64 replied 11 months ago.

click on that link to see module location.

Expert:  Hipo64 replied 11 months ago.

lights are turned on by a relay ie fusen All activity module, and thru a fuse. So I do not think this is causing the problem. However this must be repaired 100%

Expert:  Hipo64 replied 11 months ago.

Extended Activity Module is a Extension of All Activity Module(fuse box in front left side of engine compartment}

instrument cluster receives power from EAM and communication goes to it as well. after you inspect the module and if no visible damage is present, we will have to check all powers, grounds and computer data lines in einstrument cluster

Customer: replied 11 months ago.
I had that graphic and searched the entire area under the driver's side dash...there was absolutely nothing resembling that module....not sure where to go from here...perhaps I can ask for EAM diagnostic help from my local import mechanic before heading back to the Mercedes dealer....have no idea where to go from here
Expert:  Hipo64 replied 11 months ago.

Can you post the vehicle Vin#

Thanks

Customer: replied 11 months ago.
4JGAB75E65A554412
Expert:  Hipo64 replied 11 months ago.

Hi, hmm the vehicle is 2005 and must have this part, okay, is there a way you can access the instrument cluster electrical plugs? and check if there is one or 2 plugs thanks!

Customer: replied 11 months ago.
there are two "modude" type components under the driver's side dash...neither are easily accessible...one has two plugs and may come out but is not in the proper place according to the diagram link you sent...the other does not remotely seem like it is removable....very confused
Customer: replied 11 months ago.
wouldn't the instrument cluster need to be removed in order to determine that?
Expert:  Hipo64 replied 11 months ago.

Hi, yes. Cluster needs to be removed. If you would like, you can take the vehicle to your Mechanic and I can work with him.

What do you think?

Customer: replied 11 months ago.
Maybe with our local mechanic but the Mercedes tech is not so receptive to ANY suggestions or even questions...why I turned to you...he is very frustratingly disinterested in diagnosing the problem because it is intermittent...even seeing a video of the instrument cluster acting up was not enough to convince him anything is wrong....this is our last opportunity to fix this worsening problem before our warranty expires and we absolutely cannot afford to fix these issues on our own....I would certainly love it if the Mercedes tech in Burlington at Automaster/Mercedes would talk with you since the warranty company wants us to work exclusively with them but how would we facilitate that?....I would love to know if he tested/inspected the EAM....he claimed he did six hours of diagnostics and trouble shooting/wire tracing with no evidence of a problem...how can that be??
Expert:  Hipo64 replied 11 months ago.

Hi, I can work with your local mechanic. the only issue is that I am working in the shop as well and as you can see it takes sometime before I can reply. I will do my best to help.

Expert:  Hipo64 replied 11 months ago.

I believe that there should not be issue with insurance Company as this is ongoing problem that has not been resolved yet.