Eddyson

Hi everyone, first of I would like to thank the administrators for accepting me as a new member.
i have a 2013 S4 and I’m looking to replace a faulty radio module (trunk module)
The original module is part number 4G0 035 082E.
I have only been able to source out second hand radio modules that end in a D or G. The first 9 digits are the same as above.
can anyone confirm if radio modules ending in 082G
or 082D will work for my car??
one was from a Q5, other was out of a 16 S4.

SMac770

They're the same things, just different periods of use. Also, 4G0 035 080 and 4G0 035 082 are the same thing. 080 is the catalog part, 082 is the part number on the sticker on the unit. These are the MMI 3G+ radio units for facelift 8K (B8.5 A4) for US market (includes Sirius tuner). I'd go for the rev G.

rev C, through May '12 (super early MY13)
rev D, Jun '12 though Oct '12 (early MY13)
rev E, Nov '12 through May '13 (late MY13)
rev G, May '13 on (MY14+)

Eddyson

Thank you SMac770…
Does this apply for the mmi 5F unit also? Or should the 5F be replaced with the exact same part # and originally equipped?

SMac770

Similar concept for the J794. Each year, or even twice a year, there was a new revision reflecting an updated software load (nav data, etc) and maybe some hardware updates.

Eddyson

So in theory, those parts ending in a different letter should work fine.
I don’t understand why the dealer is saying the modules needs to be replaced with the exact part # and letter in order to work.

SMac770

It's certainly the surest route. They are committed to official procedure, not whatever someone could make work. Part number would of course need to be the same, from a parts ordering perspective. But for used stuff, too often you end up buying a part number stamped on the unit rather than the catalog part number you would order a new one by (same thing for control arms and headlamps, etc). And the meaning of revision letters is not the same from part to part. And newer is not always compatible. Just happens in this instance that you should be fine with a newer rev of the same part number for the radio R or the J794.

So the dealership line should be no surprise. Also note when replacing the radio or the J794, both fall under the component protection mechanism Audi made "to combat vehicle parts theft". What it really means is you'll have to have the dealership bless your parts swap for one hour labor bill before they will be fully functional.

Eddyson

An update with the mmi issue…
I have changed the mmi head unit with a part having the exact same p/n as my original.. all numbers and letter the same… no luck..
I connected a radio module from a 2014 a4. Same part number only this one ended in the letter G and mine ends in E… no luck, mmi system still won’t turn on.. I’m baffled by this.. someone suggested maybe the screen is dead but if this was the case shouldn’t I at least have audio??
I don’t know what else to try….

SMac770

That assumes the issue was the radio unit. Did the MMI system operate if you used a bypass plug on the optical cable going to the radio unit? If not, it was likely the radio unit was not breaking the optical ring, or the issue is the J794 (dash unit) itself. The problem is there's no way to interact with the J794 except over the optical ring. And if the J794 is having a problem, the optical ring goes down since the J794 is the master for all ring purposes. Whoever designed the system at Audi had zero clue about support and diagnosis.

You can find MOST optical ring bypass plugs on Amazon. It's good to get both the male and female for whatever issue you might be working, but the female one is the one you need for this task (to plug the optical cable into).

I don't know if the MMI 3G J794 shuts down on a detected screen issue. (screen = J685 = FID = front information display) Are the lights on the control buttons still lit up? If they are, have you tried the reboot to see if you get anything on the screen initially? You have to hold down the three buttons for a few seconds to bounce it. upper right soft button, then some other button, then the big dial last, hold them for a few seconds and release. But I don't know on a specifically type 8K facelift MMI 3G+ what the other button is. Some say it's the menu button. It could be in your manual.

When you first turn ignition on, can you connect to address 0x5F? Or are you never able to connect to that address? I presume the J533 (address 0x19) has a DTC about ring down?

Eddyson

We are just going by power of elimination.
The dealer supposedly did a diagnostic by pass test on all modules and all signs point to a faulty 5F unit.
By replacing the 5F, the control board and now the radio module and still the mmi won’t come to life we are thinking maybe a dead amplifier or possibly the screen..
only two lights laminate on the control board and strangely these two lights remain on even with the ignition off and car locked..
im not sure what you mean by connecting to address 5F or DTC ring down but when I first turn the ignition on, I hear a slight humbling sound from the 5F and also I have sound when I engage reverse and when parking sensors are engaged… not sure if that’s helpful…
.also I have done the hard reset several times…

SMac770

You have to consider all the components involved. For the core system, there's the J794 control module, the J685 screen, and the E380 controls. Then there's the optical ring, with it's members: J794 MMI control module, J533 CAN Gateway, R radio, and if you have B&O, the J525 sound system (amplifier).

Notice in your upper pic, you have two of the soft buttons lit up. I don't believe that's a legit state. So maybe an issue with the E380, the J794, or the wiring between. It sounds like in the ticket text you've already tried replacing the E380? But did you also replace the wiring harness from the E380 to the J794, or at least ring out the old one to confirm no crossed wires or excess resistance measurements?

"these two lights remain on even with the ignition off and car locked". That would be a bit of an issue. I'd start there. Are they lit up when the wiring harness (the big quad block one) is unplugged from the J794? There might be a short in the harness. Otherwise, the J794 is still passing 12v out to the E380 when it should be in a sleep state. If you look at the 16 upper pins in the quad block (plug A is 1-8; plug D is 9-16)

1 - NF mute for cell phone prep
2 - 12v to the E380 pin 7
3 - wake up line to/from the E380 pin 6
4 -

5 -
6 - Res HU/MU to the E380 pin 13
7 - ring-break diagnosis from the J533
8 -

9 -
10 - serial data line from the E380 pin 16
11 - serial data line to the E380 pin 15
12 - Ground for the J794

13 -
14 - Res BT from the E380 pin 14
15 - 12v for the J794
16 - ground to the E380 pin 8

Insufficient information about what Res MU and Res BT mean. The serial data lines are just RS-232.

So you see 12 and 15 are the ground and 12v lines from the car to the J794. The J794 then sends 12v and ground to the E380 via 2 and 16. So if you pull plug A (not sure if you can pull A without pulling the whole quad block first), do the lights on the E380 go out.

The beeping of the parking sensors is through a speaker in the right c-pillar space; not from the infotainment speaker system.

If it had been the amp, that should have been known from step 1. Step 1 is always put a bypass plug on the optical ring components (except the J794 of course, as there's no ring if there's no J794) and see if that works. If it does, then you put the ring slaves back on the ring one by one until it breaks. Then you know your broken component. This assumes none of the optical cables themselves are broken. I would be curious if a male plug on the J794 itself (rather than on the optical cable) would create a working ring from the perspective of the J794. If so, that's helpful, because now you can isolate the J794 from 100% of the optical bus in the car.

If they've replaced the J794 and the E380 and the R at this point, there's no point replacing the amp blindly. Tell them to correctly isolate it. If the buttons are still doing weird stuff, I wouldn't even bother with the ring. It's something more core to the J794 and E380, imo.