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W220 antenna system and Key Fob

116622 Views 88 Replies 21 Participants Last post by  wallyp
There has been alot of discussion over W220 antennas, GPS losing its location, bad radio reception, which antenna for the cell phone does what and how the key fob works. To try and clear some of the fog I am going to piece together information based on the WIS and lay it out as a reference to the W220's antenna system and how it all works.

Hopefully staying on the correct side of “fair use,” I use diagrams from the WIS, but the verbal descriptions are mine. Mindful of copyright, it will be necessary to refer to the WIS for the more detailed descriptions and technical information provided by MB. To make that easier, I have cited the document numbers so that you can check the WIS for different option codes, model years, and greater detail. You can access the WIS by subscription (annual or daily) at STAR TekInfo

Lets begin... RF signals are picked up by an antenna, In the W220 antenna for FM, TV, AM and Remote Central Locking (your key fob) are embedded in the rear glass. All rear windows have the same antennas embedded regardless of country code. There are some minor shape variations between infrared shielded glass and normal glass but both types are functionally equivalent. In the first diagram below, Locations marked 1 are for the FM bands, for Remote central Locking, and for TV (the tuners were available in Europe only). Location 2 is for AM. Location 3 is actually the sharkfin antenna on the roof; it is not in the glass. Location 4 is for digital audio broadcasts, an option offered only in Germany.

The sharkfin (on the roof) serves to receive and transmit signals when a portable cell phone is plugged in to the system via a cradle (including hybrid Bluetooth cradles that have antenna couplers built in). It also transmits Tele-Aid signals, and may transmit and receive signals for the European UHI system. In North America, most modern portable cell phones do not use the sharkfin or rear bumper antenna, but rely only on the handset’s antenna.

GPS signals are received and passed from the (powered) GPS shark fin antenna to a splitter and on to COMAND; the split incoming signal is also passed to the Tele-Aid module. The shark fin is not part of the rear glass but is attached to it.

Note that the cell phone antenna is both receive and transmit; the others are receive only. In addition, power is delivered to powered antennas in two ways: By separate copper power leads, or via the coaxial cables, which may handle both RF signals and power.

There is a backup/spare TELEAID antenna located in the rear bumper but is not used unless the primary “sharkfin” is defective, as in a rollover. The telecommunication control unit (N112) detects a failure in the sharkfin antenna (A2/49a1) and activates the bumper antennas. Reference document GF82.95-P-3001SZ for specific details.

Reference document is GF82.62-P-3106-01B

Now that we have the signals what do we do with them? Per the diagram below it seems all the entertainment and Remote Locking signals head for an amplifier.

Reference document GF82.62-P-0001A

Reference document GF82.62-p-3105-04A

The amplifier filters out the signals coming from the rear window antennas, selectively amplifies them and sends them out via coax cable to their respective control modules. For AM/FM/TV they go to the Radio or COMAND. For Remote Unlock the key fob signal goes to Overhead Control Panel Control Module.

Some basic troubleshooting ideas:

Some reception, but its pretty weak---- That would indicate that COMAND / radio and antennas are working, but the amplifier isnt passing a strong enough signal. That MAY be due to bad amplifier, poor contact between antenna and amplifier or having a metallic tint applied to the rear window glass. The in glass antennas don’t have a “hardwired” connection to the amplifier. Note the small contact points at the end of each of the arms. That’s what connects to the appropriate antennas in the back glass. (Shown upside down). Anytime you have a “touch” connection you can have gunk ( for lack of a better term ) build up that can degrade that connection.

No reception at all, including key fob unlock ---- No voltage getting to amplifier (check fuse 61 in rear fuse box) means no connection from amplifier to antennas or amplifier has suffered a total meltdown.

And that about covers the in-glass antennas. Next up is the GPS antenna.


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W220 "SharkFin" - and an inexpensive replacement

You are likely already familiar with where our "sharkin" is, that wart-like protuberence on the top of back window. The sharkfin houses 2 antennas actually. One for GPS and the other for cell phone. The GPS antenna is an "active" antenna. That is to say it has an integral amplifier as part of the antenna itself. Voltage for that amplifier is supplied via the center conductor of the coaxial cable, usually 3-5 V. (reference document GF82.62-p-0001A)

GPS signals go from the antenna thru a splitter located on the passenger side of the trunk behind the paneling (A2/6 below). The splitter is required when both TELEAID and COMAND are installed. (reference document(s) GF82.95-p-4102A and GF82.85-P-3107A)

The splitter takes the signal from the GPS antenna and sends it to both Navigation Processor and to the TELEAID Control Module (see the block diagram in the post preceding). The connection to the TELEAID is in the event of airbag deployment your GPS position info can be sent. The signals to the Navigation Processor (located on left side of trunk, behind removable panel as of 1 Sep 2003 build dates) are processed and your location calculated and displayed. Earlier model years have the nav processor mounted differently, but in the same general location; see the Phone Bulletins at Phone Bulletins for the location.

4 satellites are required for a first position calculation, 3 satellites are then required to maintain that position. 1 Satellite is all that is needed to update your Date/Time/clock. Your course of travel is determined by the sequence of position fixes calculated approximately 50 times a second. This is called Continuous Position Finding (reference document GF82.61-P-3007BA and AN82.85-P-0002M). Additional position fixing and direction is calculated and applied using all 4 wheel speed sensors, an internal Yaw Sensor Unit in the Navigation Processor itself and digitized map data. This is known as Map Based Position Finding. (reference document GF82.61-P-4001BA ). The Navigation Processor uses both methods simultaneously and is referred to Compound Position Finding.

Intermittent loss of GPS satellite signals due to tunnels, high buildings and the like, will degrade position accuracy depending on the length of the signal loss. Lose the signals long enough and it will eventually put you "Off Road". Long term loss of GPS signals can also be attributed to a malfunction of the integral amplifier in the GPS antenna itself or moisture intrusion into any of the connections between the antenna and the Navigation Processor - at the splitter for example. When this happens the Navigation Processor doesn’t have a GPS fix as a starting point and applies Map Based Position finding to its last known good fix. In other words, it thinks your are quite a distance away from where you really are and until you get another GPS fix, i.e. fix the antenna/connection problem. I had that happen to me. Turns out my antenna is toasted.

A cheap fix is a $20'ish active GPS antenna with blue FAKRA connector, preferably a right angle one. For the dollar conscious amongst us, look here Note the picture shows a straight FAKRA connector, you must specify in the order a R/A ( right angle ) FAKRA C type connector. 3 meter long coax. They have free shipping and you can use paypal. The company is located in Shenzhen China.

For those preferring a stateside vendor ( at least the phone number is 212 NYC area ) look here Also has free shipping and uses paypal.

Place it in the middle of the parcel shelf, between the center headrest and the edge of the sun shade, run the coax under headrest then along top back edge of back seat (finger pushed the coax between back seat top and parcel shelf) to base of C pillar, thence to the rear squeezed under edge of parcel shelf, thru hole into trunk. Straight blue FAKRA was a bit of a booboo, need right angle but I will leave the nav unit not completely seated by 3-4 mm for now to avoid crimping the coax. 

Works just okay, GPS position reset nicely after about 3 minutes. I hold 2-4 satellites pretty much most of the time with momentary 5 or more randomly. Having to look through the Infrared protected and tinted back glass, half the sky obscured in metal roof and no real adequate ground plane pretty much hobble it. But I didnt want to try and roof mount it and run the coax under the back glass seal. Thrown up on the roof I have a steady 9-11satellites received.

UPDATE A much more detailed method of mounting the replacement GPS "puck" is here. For all intents and purposes is invisible and works extremely well ....


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Thanks for all of that information and a great thread, Ex-Fed - it is referenced in the Encyclopedia, and also in the W215 forum, since it applies to that model as well.

This thread has been kept closed while Ex-Fed built it, so that the reference information could be kept together. It is now open.

One additional thought - the original Mercedes Sirius/XM antenna was a separate one, initially mounted atop the middle of the trunk - not the most attractive location, and it required a hole in the middle of the trunk lid. Much the way Ex-Fed has described the substitute for his malfunctioning GPS antenna, 3rd party alternatives exist for the Sirius/XM antenna. Some may be mounted on the rear parcel shelf, as Ex-Fed did; others have had success going through the firewall and mounting the antenna in the A/C intake plenum in front of the windshield.
This research project could not have been finished without a TON of help. Primarily from Skylaw but significant input from Bullethead D and Diesel Benz and others helped point me in directions I had not considered. Thanks gentlemen :thumbsup:

One additional thought - the original Mercedes Sirius/XM antenna was a separate one, initially mounted atop the middle of the trunk - not the most attractive location, and it required a hole in the middle of the trunk lid. Much the way Ex-Fed has described the substitute for his malfunctioning GPS antenna, 3rd party alternatives exist for the Sirius/XM antenna. Some may be mounted on the rear parcel shelf, as Ex-Fed did; others have had success going through the firewall and mounting the antenna in the A/C intake plenum in front of the windshield.
I haven't been able to check exact build date, but wasn't the Nav Processor the bottom box on the COMAND stack in the center dash area for MY 03 and earlier? If so, then the A/C plenum area is a brilliant solution. I would not use it on the trunk mounted Nav Processors models, the signal loss for that long ( call it 10M or 33 feet ) of a coax run would be prohibitively high.

Here comes some Geek Speak, you have been warned !

RG174 coax on the cheap alternate GPS antennas has about 1.5 db loss PER FOOT at GPS satellite frequencies of 1.5 GHZ. So a 33 foot (10M ) run would be on the order of a -45 db loss at the processor. The vast majority of those alternative antennas only have +25 to 30 db gain at the antenna pre-amp output. So signals arrive at the processor after 33 feet of coax 15 db down from no antenna at all and basically unusable. Will save discussion of signals below the noise threshold and signal to noise ratio for another time ;)

The upshot of this is, keep the coax as short as possible for best performance.
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Great info, and your efforts are greatly appreciated.

This post is an attempt to add extra real-world info, not an attempt to attack or argue with your info...

I spent quite a bit of effort to improve the cell phone system in my USA 2003 S430. When I purchased it a year ago, it had the V60 cradle and Bluetooth puck installed, along with the voice control system. The Bluetooth puck paired with my Motorola Razr Maxx HD. I could not utilize the phone's contact list, but did rebuild the car's contact list so as to use the voice control system.

Since I do travel some, I wanted better phone performance than I could get with the cell phone's antenna thru the S430's windows. I purchased a Wilson Sleek booster system, which came with a magnetic antenna. Performance (measure by network signal strength, not the display bars) improved a lot with the antenna on top of the car, but I could not accept having the cable run out thru the door opening and across the roof.

To shorten a long story, I ended up putting the cradle and puck in the lower console compartment, the booster and phone in the upper compartment, and using the existing co-ax running to the left rear fender. I removed the TeleAid/phone switch and the linear compensator, and disabled the obsolete analog TeleAid system, and hooked the Wilson booster to the rear bumper antenna.

There was no sign of any existing connection to the sharkfin anywhere in the system. The GPS Nav system works well (well, the receiver does - the user interface sucks)

No idea whether the antenna setup was as-installed by the factory, as-installed by the dealer, or as-installed by someone else. It certainly looked totally original - no touch of jury-rigging or poor installation.
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Great work - thanks to ex-fed:thumbsup:
Before I converted to a Chinese head unit I had the strangest system. Stock COMAND head unit and Bluetooth puck with tail. It sometimes took over 1/2 an hour to find GPS satellites BUT as soon as I powered on my cell phone it found satellites right away. It did not matter whether the phone had GPS or not.
@ Wally P

From what I can see, the factory/dealer config shown below has the bumper antenna terminating at N123/4 TELEAID Emergency Call System Control Unit (under the back seat.)

N123/4 has the function of establishing a phone connection, via the telephone antenna ( a2/49a1 ). If the telephone antenna is defective, e.g. in the event of a rollover, emergency antenna are available in the rear bumper. N123/4 detects the telephone antenna failure and activates the emergency antenna automatically. ( reference document GF82.95-p-2006sx )

Now, having said that, I submit that you MAY be actually using the sharkfin for cell phone use. Based on your post, you used ( I am assuming ) the coax that was in the center armrest originally. The only visible path for that coax was to the trunk and not to the rear seat area.

I use "MAY" above because, as you pointed out, a non-MB shop may have run separate coax from the bumper antennas to the console. No telling without some serious "dumpster diving" and wire tracing.

Practically speaking, you have system that works for you, so its all good ! :thumbsup:


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I actually removed the rear seat and physically traced the co-ax from the console, under the carpet and rear seat to the trunk and the switch and linear, and from there thru the rear of the trunk floor to the antenna. No connection going up anywhere on the lead...
I am definitely using the rear bumper antenna.
Traced leads as far as I could - hers's what I found

Well, well. Only two weeks ago, I was eating turkey for Thanksgiving. Now it is time to eat crow. The original post in this slot contained incorrect information; I have seriously revised it to make it more accurate. In one of the posts below, Bullethead_D observes that I had identified (in a now-deleted photo) the Audio Gateway as the Tele-Aid Control Module; he is absolutely correct. While his comment at post #12 below will not make sense following these revisions, his observation was entirely correct for the original post that he referenced.

Bottom line (so you won't have to wade through this): Although the block diagram in Ex-Fed’s post above was labeled (in the WIS) for cars having D2B fiber busses, I believe it is also correct and applicable to cars having the MOST bus. Indeed, the plug-in or antenna-coupled cell phones will use both the Shark Fin antenna and the rear bumper antenna, and the antenna in use at a given time is controller by the Tele-Aid Control Module. Here is why.

Trying to get to the bottom of the question of where the center console antenna connects, and whether the signal from the center console is sent via the shark fin antenna, I pulled my back seat out, and also opened up the equipment bay on the left side of the trunk (photo below), to trace antenna leads.

NOTE: My car is an '05; an '06 with the optional cell phone harness will be the same. However, see the phone bulletins at for the equipment bay configuration for earlier models.

The Tele-Aid Control Module is indeed under the passenger side of the rear seat bench, next to the rear SAM (first photo). Note the two coax antenna leads coming from the module, plus one of what seems to be a "sharkfin lead" (shown on Ex-Fed's photos at post 15 below). According to the block diagram, I would expect 3 antenna connections to the Tele-Aid Control Module, and that seems to be the case. The coax leads loop around the module and enter cable harnesses that that are firmly attached to the rear bench support structure (foreground of the first photo), and seem to go in opposite directions (left and right) – that makes it difficult to trace them exactly, without detaching the harnesses and ripping open the tape. Sorry, folks, I just wasn’t going to go that far! Because I did not remove the module, I could not verify exactly which harness each lead went into, and therefore, where it ultimately went in the trunk. And, it it is still no fun to pull up the molded noise barrier insulation, either.

Also making things difficult is that the antenna lead from the center console appears to go into the rear seat area and along the back door opening, then into the trunk. It does not go quite that directly. It enters one of those harnesses under the back seat support structure, so I found the exact routing difficult to trace for the same reason as the leads from the Tele-Aid Control Module.

In the trunk, there are two coax leads that cross the trunk under the parcel shelf. In the photo below, these are labeled “B” and “C.” Lead “B” connects to a short lead "A" that goes directly to the rear bumper antenna. Lead “C” goes through a grommet in the left rear wheel well and I believe into the rear seat area. I could not determine its final terminus, but my guess is that it goes to the Tele-Aid Control Module.

Removing the platform containing the CDC, the nav reader, the MHI controller and the antenna switch, and also removing the linear compensator and its bracket, reveals the tangle of leads and harnesses in the third photo, below.

Again, lead “B” connects to lead “A”, which goes directly to the rear bumper antenna (Lead “A” is labeled in two locations, because it is hard to see in the photo). The connector for lead A and lead B is behind the uppermost hole for mounting the Linear Compensator bracket.

There are three coax leads, labeled 1, 2 and 3, coming from a harness that also carries copper wire power components to the bay. Lead 1 is labeled “Antenne” and goes to the “Antenna” connection on the antenna switch. According to the Phone Bulletin for the ’05, this is the “main antenna lead.” Lead 2, labeled “Handy” (a term Germans use for cell phone) goes from the harness to the Linear Compensator. Lead 3 is labeled “LCT” and according to the phone bulletin, is the Tele-Aid lead; it connects directly to the “LCT” port on the antenna switch.

Lead 4 has only a Tyco manufacturer’s label, and is a short lead connecting the Linear Compensator output (from lead 2, labeled "Handy") to the antenna switch “Booster” port. In essence it is a continuation of Lead 2, carrying an amplified signal. Because it is somewhat difficult to make out in the photo, Lead 4 is labeled twice.

Thus, essentially, all three of the coax leads coming from the harness behind the MHI control unit and linear compensator connect to the antenna switch.

Although I was not able to positively trace the other terminus of each lead (which would have answered the question definitively, with no guessing), from what I can see, the installation is likely consistent with Ex-Fed’s block diagram. One would expect to see three antenna connections at the Tele-Aid Control module, and they are present. The coax leads in the trunk to the rear bumper antenna, to the linear compensator, and to the antenna switch are all present and in accordance with the phone bulletin (though the linear compensator and antenna switch are not depicted on the block diagram). While it bugs me not to be able to see where each lead physically connects, my old back is just too sore for me to tear out all of the existing, factory-installed wire harnesses under the back seat, to see - especially for a system that is experiencing no malfunctions!! But I have seen enough to conclude that a cell phone having an antenna plug in its cradle (e.g. StarTac, TimePort, V60 or V710), or one that is being used in one of the ”hybrid” Bluetooth cradles that had an antenna coupler (e.g., RAZR), could utilize the Shark Fin antenna or the rear bumper antenna; the Tele-Aid system does so as well, and the Tele-Aid Control Module controls the antenna that is used.

In North America cell phones that do not use a coupler or a cradle rely only on their own internal antennas, only.

The WIS does reference other documents that apply to cars equipped with Keyless Go, Remote Heater, Digital Audio Broadcasts (Germany), Remote Start (Germany), and COMAND options (both U.S. and Euro) that could result in some differences from the bock diagram in the first post. However, they should be the same regarding cellular phone and GPS systems.

In addition, there are several reasons why one might route the console antenna lead direct to the rear bumper antenna. 1) An owner installed the system, did not subscribe to Tele-Aid, and going straight to the linear compensator (bypassing both tele-Aid and the antenna switch) was the easiest way to do it; 2) Tele-Aid had failed or given trouble indications (very common in analog-only systems after the North American analog cellular network was disabled several years ago), and was disabled using DAS. That would have disabled both the shark fin and bumper antennas. In this case, a tech may well have re-done the connections straight to the linear compensator to keep the portable cell function working. There could be other reasons, but those are two that stand out.


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Wow! You have gone to a lot of trouble to check this out!

That means that now I have to go back into the system to see what I might have missed...

If I am using the "emergency" bumper antenna for the cell phone, I might well get better performance from the shark fin cell antenna.

My car had the TeleAid system, since I was getting an error message every time that I started the car, telling me that the TeleAid was not working. I stumbled into a way to use the STAR system to disable the TeleAid (much earlier than the cell phone booster installation and the associated simplification of the antenna system). The GPS and the cell phone continued to work after the TeleAid was disabled.

After I removed the antenna switch and the linear compensator, the cell phone and GPS both continued to work.

I will try to find the antenna leads from the shark fin and see where they lead, and will report back. It might take a few days - this is a pretty busy time.

I know that you aren't doing this for me, but I really appreciate it.
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Hi Warren,

I'm sure - the device you titled "tele aid control module" is the audio gateway. For me it is strange to see the voice control module behind that panel. For more support please give me your VIN via PM.

The shark fin antenna for cell phones is a passive antenna - that is, it is not powered (in contrast to the GPS antenna). Therefore you should be able to make the switch. I don't know if it will give you better reception - the bumper antenna signal is boosted by the linear compensator. There is a possibility it is the stronger signal.

Thanks for your offer - PM sent!

As one can tell from a reading, without pulling the equipment in the lower part of the bay, I had to surmise some things. I'll try to go into it again today (should have some more time) and this time pull that stuff to verify connections and also part numbers that I could not see yesterday. If I'm wrong, I'l correct the post - thanks for your observations!

I believe I am correct on the VCM though - it is located where the phone bulletin says to put it. Perhaps I have used a misleading term - it is behind the aluminum panel that the amp is located on; it is NOT behind the plastic vent panel for the bay. I hope that resolves it. I'll know more when I get into it hands-on.

NOTE: My car is an '05. An '06 will be the same. However, the VCM location and other equipment bay configurations will be different in earlier models. See
sharkfin leads are run from under sharkfin, under trim piece(s) along top, right side and right bottom corner of back glass. The thru rubber grommet into upper right corner of trunk area. Routing to this point is generic to all w220's thru MY10. ( pictures in a while )
Reference Document AR82.70-P-8951I dated Mar 17, 2010.

From that point, installed options and model years come into play. Will try to break it down some if I can later.

First pic:
1= sharkfin base
2= top trim piece
3= coax leads

Second Pic:
3= coax leads
4= trim clip
A= rubber grommet into cable duct A into trunk

Third pic: Broader view covering second pic area. Note trim is still attached and weather seal is being lifted to show grommet.
5a-5b = rear glass trim molding

Fourth pic: area in trunk coax leads come into. GPS coax would go to splitter ( if Teleaid equipped ) then across back of upper trunk to Nav Processor. Cell coax goes thru a break point connection as shown in fourth pic ( no Teleaid ) or a break point connection under splitter ( w/Teleaid )


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@ all
Before starting further investigation - Skylaw has a car delivered 10-14-2004 with code 359 "TELEAID LOW COST USA WITH CELL PHONE PREINST. UPCI" and CODE 530 "COMAND DVD APS USA WITH NAVIGATION". Code 813 (or other for USA) "LINGUATRONIC=voice control" and 388 MOBILE PHONE UHI are absent.

Do you think that pe82.95-u-2101-99sl and pe82.70-u-2101-99sk are the right documents?
I do not have those documents in my WIS, I go as far as PE82.95-P-2101-99SK. Guessing I don't have a few updates.

Went ahead and ordered C3 STAR hardware and software. Should be updated thru 7/2013. Should arrive between 24th and New Years.

Decent deal if it doesn't turn into a smoking crater on first attempt to use it. Less than $300 for all including shipping.
@ all
Before starting further investigation - Skylaw has a car delivered 10-14-2004 with code 359 "TELEAID LOW COST USA WITH CELL PHONE PREINST. UPCI" and CODE 530 "COMAND DVD APS USA WITH NAVIGATION". Code 813 (or other for USA) "LINGUATRONIC=voice control" and 388 MOBILE PHONE UHI are absent.

Do you think that pe82.95-u-2101-99sl and pe82.70-u-2101-99sk are the right documents?
Actually, my car has linguatronic and Mobile phone (MHI - not UHI) installed. Always has.
... Always has...
Hi Warren,

you are the first owner? Those things have not been retrofitted after leaving stock (e.g. by the dealer)? I will send you a PM with all codes of the accessable datacard - please check against the codes printed in your car document.
I can't say, Bullethead_D. The MHI and voice control were on the window sticker when I bought it, and they were installed. I bought the car from a dealer as a repo about 6 months after its first sale new, to a corporate officer. It had under 5,000 miles on it. It did not have the phone cradle or a handset - I had to buy those extra. But it did have the MHI contact plate, and the rest of the MHI system, as well as voice control (linguatronic) already installed. Ordinarily when those items are ordered, they are installed by an MB Preparation Center at the Port of Entry into the U.S. The installation in my car does match up to the phone bulletin,

So when and where they were installed I cannot say - but it was before I bought it, and it looks like the POE prep center installation.
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