Hello everyone, thanks for any help in advance! Does anyone have any ideas on either bypassing or replacing the Emergency Call module (Motorola module)? Specifically, here's what I'm wondering and why:
Main issue:
To troubleshoot the Fuse 8 circuits (Transfer Case and Emergency Call circuits):
To trouble the Emergency Call circuit:
Does anyone know if I can simply swap in a module from another ML? The part numbers is A203-820-39-85. I am confident that I can get another module from the junkyard or ebay. I also have access to another W163 (my sister's '03 ML350), and so I was thinking about swapping in her module to see if that works, then I'd just get one at the junkyard or ebay to replace the apparently faulty module on the ML500.
Alternatively, is there a repair for the module? (ie, some resistor needs resoldering, or something like that?)
Here's a little more info, if it is helpful:
About the Emergency Call module (part #A2038203985):
As far as I can tell, there are two fiber optic cables in/from this module: these two fiber optic (FO) cables come out with the big connector when you disconnect it. According to the wiring diagram, the two FO cables are:
"A2/56" ("Radio/Nav Unit") and
"X39/39 ("Handy Connector").
With the module disconnected, I know that I have both the FO loop open and the Emergency Call module electrical circuit open. I am thinking that worse case scenario I might have to bypass the Emergency Call module's role in the FO loop to close to FO loop so that the radio will work.
Has anyone done this? Would a simple loop connector work? Some quick research (youtube video) indicated that connector A0005453384 might work as a bypass?
Looking at the wiring diagram, the other inputs/outputs of the Emergency Call modules are:
Looking at this list, I would suspect that if I turn on the vehicle with this module disconnected, I would at least get an SRS code and also the radio would not work. Along these lines, is it possible that something in the SRS system is attempting to wake-up the Emergency call module, as if the airbags have been deployed? I'm just thinking up-circuit of the Emergency call module, in case there's an issue somewhere else (though I think its the module, which is why I'd like to try a swap if that's safe).
My limited understanding of the Emergency call system is this: back when this system was supported (pre-2008), if the airbags deploy, the system would have done all these operations automatically:
Then it would make an emergency call to the MB emergency center, and send the following information to MB's response team:
The system is tied into the radio (Radio/Nav) and CTEL (Cell Telephone) module, and the VCS (Voice Command System), and CD changer, etc. I'm not yet clear with how it all works exactly.
Any help would be great! Thanks in advance : )
- Can I replace the module with one from another vehicle? I know the module is VIN-encoded because when the Teleaid Emergency system was in effect (it is long since totally obsolete), the unit would send the VIN to the emergency response center. But does the module actually need to be VIN-paired? Specifically, will a non-VIN-matched module swap in alright, or will that be blocked by some other system?
- What errors/lights will display/codes store if the ML is operated with the Emergency Call module disconnected?
Main issue:
- The battery on our '05 ML500 recently started discharging within a couple of days.
- I measured a 330 mA parasitic draw at the battery which persists for hours and hours after the engine is shut off.
- I located the offending circuit after measuring 290 mA draw across Fuse 8 (25 Amp Maxi Fuse) in the engine bay fuse box.
- I checked the map, and Fuse 8 protects the Transfer Case circuit and the Emergency Call circuit.
To troubleshoot the Fuse 8 circuits (Transfer Case and Emergency Call circuits):
- I removed Fuse 8, then went back to measure current draw at the battery: current draw dropped from 330 mA to 30 mA! So, in other words, with those circuits open, the parasitic draw was gone and the system was back to normal. Therefore I concluded that either the Transfer Case or Emergency Call circuit was the culprit for the current draw.
- I reinstalled Fuse 8 to the fuse box. By a lucky chance, I noticed as I walked by the cabin that the "SOS" system was trying to make an "emergency call", because it was displayed so on the Radio/Nav screen. I watched as it tried to complete a call for a minute or two. The call failed, of course, since MB has not supported these systems in over a decade.
- So, I thought perhaps the Emergency Call module circuit was more likely the issue than the Transfer Case circuit and decided to troubleshoot that circuit first.
To trouble the Emergency Call circuit:
- I printed out the circuit diagram from WIS, so I have an idea of the various inputs/outputs from the Emergency Call module. The R&R instructions for the Emergency Call module state to remove Fuse 8 before disconnecting the module.
- Back in the engine bay, I removed Fuse 8 again.
- Back in the cabin, I disconnected the electrical connector to the Emergency Call module. This module says "Motorola" and has an orange sticker on it, and is located under the passenger seat.
- With that module disconnected, I reinstalled Fuse 8 and checked for voltage across the fuse: there was no voltage across the fuse (previously there was about 0.7 mV, corresponding to the 290 mA current flow).
- I also checked amperage at the battery, and current draw was again down to 30mA (where it should be!), so it seems that the Emergency call module is the cause of the drain.
Does anyone know if I can simply swap in a module from another ML? The part numbers is A203-820-39-85. I am confident that I can get another module from the junkyard or ebay. I also have access to another W163 (my sister's '03 ML350), and so I was thinking about swapping in her module to see if that works, then I'd just get one at the junkyard or ebay to replace the apparently faulty module on the ML500.
Alternatively, is there a repair for the module? (ie, some resistor needs resoldering, or something like that?)
Here's a little more info, if it is helpful:
About the Emergency Call module (part #A2038203985):
As far as I can tell, there are two fiber optic cables in/from this module: these two fiber optic (FO) cables come out with the big connector when you disconnect it. According to the wiring diagram, the two FO cables are:
"A2/56" ("Radio/Nav Unit") and
"X39/39 ("Handy Connector").
With the module disconnected, I know that I have both the FO loop open and the Emergency Call module electrical circuit open. I am thinking that worse case scenario I might have to bypass the Emergency Call module's role in the FO loop to close to FO loop so that the radio will work.
Has anyone done this? Would a simple loop connector work? Some quick research (youtube video) indicated that connector A0005453384 might work as a bypass?
Looking at the wiring diagram, the other inputs/outputs of the Emergency Call modules are:
- Starter switch (the system apparently runs a check on itself and the SRS system when the ignition key is turned to ON)
- Data Link Connector
- CTEL (phone call module) and Frequency Switchover module (for calls)
- Trunk/tailgate switch
- Restraint System Control Module
- AAM (for Alarm and Door Unlock function)
- Roof Operating Unit Switch Module (the red SOS button)
- Hands-free Microphone
- Traction Systems Module (Left Rear Speed Sensor)
- Emergency Call Speak
- Rear Bumper Antenna
- Cell Phone & GPS Roof Antenna
Looking at this list, I would suspect that if I turn on the vehicle with this module disconnected, I would at least get an SRS code and also the radio would not work. Along these lines, is it possible that something in the SRS system is attempting to wake-up the Emergency call module, as if the airbags have been deployed? I'm just thinking up-circuit of the Emergency call module, in case there's an issue somewhere else (though I think its the module, which is why I'd like to try a swap if that's safe).
My limited understanding of the Emergency call system is this: back when this system was supported (pre-2008), if the airbags deploy, the system would have done all these operations automatically:
- unlock the doors
- turn off the radio and allow the hands-free microphone/speakers to connect the driver to the emergency response person
Then it would make an emergency call to the MB emergency center, and send the following information to MB's response team:
- current position of vehicle (GPS)
- route before accident
- direction of travel
- VIN
- drive type
- estimated number of people in vehicle
- time of accident
- language setting of the multimedia system
The system is tied into the radio (Radio/Nav) and CTEL (Cell Telephone) module, and the VCS (Voice Command System), and CD changer, etc. I'm not yet clear with how it all works exactly.
Any help would be great! Thanks in advance : )
