Antenna booster on avant & radio reception issue?

[streamline]

I am having issues with FM reception, in my research I have heard antenna booster could be the culprit. I looked in rear head liner and did not see the module, is anyone away where it is located on an avant? or has anyone had this issue before?

[Smac770]

What's your build date and do you have MMI (controls around the shifter) or not?

[streamline]

I have B&O MMI 2G High

[Smac770]

Sounds like you tried to follow instructions for a sedan, looking at the ceiling.

For '09 Avant MMI 2G:

- R24 amplifier, 8K9 035 225 A, around the glass in the rear lid (you'll need to pull off the lower and then upper plastic trim panels to get at it). Unclear if it'll be high left, high right, or top center, but it'll be obvious. I assume this is attached to the antenna trace in the rear glass.
- R113 amplifier, 8K9 035 225 B, in the right C-pillar. I assume this is attached to an antenna trace in the right rear glass.
- The output from these two amps (FM2 from R24, FM3 from R113) goes to the R112 amplifier/switch, 8K9 035 225 K, which is located behind the cargo area left side panel (it doesn't appear you can get to it by just removing the little cover door). I assume this one is attached to an antenna trace in the left rear glass. It's also the switch unit that picks which antenna feed (FM1, FM2, FM3) to pass to the radio (the HF and IF outputs to the R radio unit) [assuming].

It's unclear when MMI changed from this switch diversity system back to the phase diversity system used by the CAN system. Repair manual says Nov 1 '08, ETKA says Jan 12 '09. Both would seem tied to the change from MMI 2G to 3G. But parts.audiusa.com seems to imply it didn't change till the facelift. The MMI phase diversity system (for us in the US, ie no DAB or TV complications) dropped the R113 and replaced the R112 with a simple 8K9 035 225 (ie, similar to the R24 and R113), relocating it to the left C-pillar. The R24 FM2 and R112 FM1/AM output then both go to the radio R which implements the phase diversity solution.

In both cases, R112 has a "CLS" connection to the J393. Gray farka plug. No clue what CLS means.

[Gunnark100]

In both cases, R112 has a "CLS" connection to the J393. Gray farka plug. No clue what CLS means.

Should be central locking system (antenna connection).

For op, any errors under radio(56), normally it should show if any antenna amplifier/connection has fault, but not always.

[Smac770]

Ah ok. So that's what the coax cable going to the J393 is. The signal from the antenna for the key fob buttons.
CLS: R47 aerial -> R112 amplifier -> J393
Interesting that they bring that antenna signal to the J393 as coax through an amplifier, but the signals from the three advanced key antennas (R137, R138, R200) are on normal wires direct. I assume the difference is the signal sensitivity involved, as the key fob buttons operations involve a much larger range.

That's one thing, for all their other extensive documentation, that Audi blows at cataloging. The avant aerials.

[streamline]

Apologies guys I am a little confused with the different modules, but here are the VCDS results:

-------------------------------------------------------------------------------
Address 56: Radio Labels: 4E0-910-541.lbl
Part No SW: 4E0 910 541 T HW: 4F0 035 541 N
Component: TUNER EU/US/RDW H42 0630
Revision: 00000000 Serial number: 357HW087507802
Coding: 0000002
Shop #: WSC 06335 000 00000
VCID: 31630B1DA8327B1

3 Faults Found:
00446 - Function Limitation due to Under-Voltage
002 - Lower Limit Exceeded - Intermittent
Freeze Frame:
Fault Status: 00100010
Fault Priority: 7
Fault Frequency: 3
Reset counter: 40
Mileage: 225845 km
Time Indication: 0
Date: 2019.03.16
Time: 11:49:43

00856 - Radio Antenna
007 - Short to Ground
Freeze Frame:
Fault Status: 01100111
Fault Priority: 5
Fault Frequency: 12
Reset counter: 0
Mileage: 221461 km
Time Indication: 0
Date: 2018.11.05
Time: 08:25:03

00858 - Connection; Radio ZF Output to Antenna Amplifier
011 - Open Circuit
Freeze Frame:
Fault Status: 01101011
Fault Priority: 5
Fault Frequency: 12
Reset counter: 0
Mileage: 221461 km
Time Indication: 0
Date: 2018.11.05
Time: 08:25:04

[Smac770]

Those DTCs are really old. Have you tried clearing them and seeing what comes back?

Not sure what ZF is, nor why the radio would have an output to the antenna amp. The antenna amp calls its outputs to the radio HF and IF for that generation.

I'd pull the left side cargo area panel and find the R112 unit. Then unplug and replug the farka cables on it and on the radio unit (the second from the top unit in the electronics stack in the back left) and see if that clears it up. I had a problem with my backup camera and it turned out just to be a loose connection of the farka cable at the unit in the dash. Unplug, replug, resolved.

https://www.ebay.com/itm/Audi-A4-8K-...-/274055937012
The two cables on the white plugs are what go to the radio.
The two cables on the yellow plugs are what come from the R24 and R113.
The cable on the gray plug is the central locking system signal that goes to the J393.

[Smac770]

Ok, ZF = IF
zwischenfrequenz = intermediate frequency

Finally, an overview of the switching diversity system that's somewhat relevant to our system.
https://www.vag-navisystems.com/info...-radio-26?en=1
though the usefulness ends there. Obviously, none of the amplifier locations or identifications are like our car.

So at least the DTC points to the IF signal, which is the farka plug not at the corner of the radio unit. The one at the corner is the HF farka cable. Then the IF one, then the MOST optical plug, then the wiring plug in the other corner.