Ultimate battery drain - parasitic draw

[Jimmyhummus]

Hi all - looking for some extra insight into an issue with a parasitic drain on my B8 (a4 09 2.0T). The background story is that the alternator began making some loud noises, ended up replacing and noises went away. Shortly after the battery died and was time to replace the battery. The battery was a like for like prior replacement Bosch however the alternator was a reman from pep boys. I ended up taking the first one back because it failed a diode test with my multi meter - basically check the B+ both directions. Second one no issues but still questioning because I can’t seem tp find an issue resulting in about 500 mA of draw. I pulled all fuses and relays one by one and still has the same draw (2 door panels and trunk). It wasn’t until I pulled the d pin from the alternator that it went basically to zero.

I ended our running codes and below is what I got. I bit the bullet and ordered an OEM alternator from eBay but want to make sure nothing else is going on alongside.

Thanks for taking a look.

01-Engine -- Status: OK 0000
02-Auto Trans -- Status: OK 0000
03-ABS Brakes -- Status: OK 0000
04-Steering Angle -- Status: OK 0000
05-Acc/Start Auth. -- Status: Malfunction 0010
08-Auto HVAC -- Status: OK 0000
09-Cent. Elect. -- Status: OK 0000
15-Airbags -- Status: OK 0000
16-Steering wheel -- Status: OK 0000
17-Instruments -- Status: Malfunction 0010
19-CAN Gateway -- Status: Malfunction 0010
2E-Media Player 3 -- Status: OK 0000
42-Door Elect, Driver -- Status: OK 0000
46-Central Conv. -- Status: Malfunction 0010
47-Sound System -- Status: OK 0000
52-Door Elect, Pass. -- Status: OK 0000
53-Parking Brake -- Status: OK 0000
56-Radio -- Status: Malfunction 0010
62-Door, Rear Left -- Status: OK 0000
65-Tire Pressure -- Status: OK 0000
72-Door, Rear Right -- Status: OK 0000
77-Telephone -- Status: OK 0000
-------------------------------------------------------------------------------
Address 01: Engine (DL0MA-CAEB) Labels:| 06H-907-115-CAB.clb
Part No SW: 8K2 907 115 AL HW: 8K2 907 115 D
Component: 2.0l R4/4V TF H14 0001
Revision: E1H14---
Coding: 0104010A190F0160
Shop #: WSC 37332 000 1048576
ASAM Dataset: EV_ECM20TFS0118K2907115AL 001001
ROD: EV_ECM20TFS0118K2907115AL.rod
VCID: 79AF116969564B5F8EB-802C

No fault code found.
Readiness: 1110 0101

-------------------------------------------------------------------------------
Address 02: Auto Trans (J217) Labels:| 0B6-927-156.clb
Part No SW: 8K0 927 158 C HW: 0B6 927 156
Component: 0B6 20TFSIUSA H04 0052
Revision: --H04---
Coding: 001002
Shop #: WSC 08310 444 100135
ASAM Dataset: EV_TCMAL651 A01006
ROD: EV_TCMAL651.rod
VCID: 3635DA5518C86427239-8062

No fault code found.

-------------------------------------------------------------------------------
Address 03: ABS Brakes (J104) Labels:. 8K0-907-379-V1.clb
Part No SW: 8K0 907 379 AB HW: 8K0 907 379 AB
Component: ESP8 quattro H04 0060
Revision: -------- Serial number: --------------
Coding: 150500
Shop #: WSC 02399 823 56573
VCID: 79AF116969D64B5F8EB-802C

No fault code found.

-------------------------------------------------------------------------------
Address 05: Acc/Start Auth. (J393) Labels:. 8K0-907-064-05.clb
Part No SW: 8K0 907 064 F HW: 8K0 907 064 F
Component: BCM2 1.1 H80 0141
Revision: 00002001
Coding: 090100
Shop #: WSC 02399 823 56573
VCID: 3333E3410B3A710F047-8066

Subsystem 1 - Part No SW: 8T0 959 754 A HW: 8T0 959 754 A
Component: FBSAUDIB8 IDG H37 0060
Serial number: 0508000050576013

Subsystem 2 - Part No SW: 8K0 905 852 D HW: 8K0 905 852 D
Component: ELVAUDIB8 H36 0041
Serial number: 0208000061226013

1 Fault Found:
01330 - Central Control Module for Central Convenience (J393)
013 - Check DTC Memory
Freeze Frame:
Fault Status: 01101101
Fault Priority: 6
Fault Frequency: 1
Reset counter: 15
Mileage: 215954 km
Time Indication: 0
Date: 2008.05.27
Time: 00:28:00


-------------------------------------------------------------------------------
Address 08: Auto HVAC (J255) Labels: Redir Fail!
Part No SW: 8T1 820 043 AA HW: 8T1 820 043 AA
Component: KLIMA 1 ZONE H06 0140
Revision: A1000000 Serial number: 0102.09.081383
Coding: 64002000
Shop #: WSC 02399 823 56573
VCID: 70B92C4D3AAC0A17395-8024

No fault code found.

-------------------------------------------------------------------------------
Address 09: Cent. Elect. (J519) Labels:. 8K0-907-063.clb
Part No SW: 8K0 907 063 D HW: 8K0 907 063 D
Component: BCM1 1.0 H22 0253
Revision: 05022001 Serial number: 00000000116317
Coding: 690000B1063C00010000080300007F5F0F1452080000002100 0000
Shop #: WSC 02399 823 56573
VCID: 3039EC4DFA2C4A17795-8064

Subsystem 1 - Part No SW: 8K1 955 119 A HW: 8T1 955 119 Labels: 1KX-955-119.CLB
Component: WWS 110908 H06 0070
Serial number: SWF08090115307
Coding: 00FD11

Subsystem 2 - Part No SW: 8K0 941 531 F HW: 8K0 941 531 F
Component: E1 - LDS H07 0070
Serial number: 00000000000409081041

Subsystem 3 - Part No SW: 8K0 907 410 A HW: 8K0 907 410 A
Component: UGDO HL US H04 0060

No fault code found.

-------------------------------------------------------------------------------
Address 15: Airbags (J234) Labels:| 8K0-959-655.clb
Part No SW: 8K0 959 655 F HW: 8K0 959 655 F
Component: AirbagVW-AU10 H27 0410
Serial number: 0039KD146PNI
Coding: 303836354230303030304A55304C384B3053
Shop #: WSC 02145 785 00200
ASAM Dataset: EV_AirbaECUVWAUDI010 A02007
ROD: EV_AirbaECUVWAUDI010_A02.rod
VCID: 40D9BC8D4A0CDA97895-8014

Seat occupied recognition:
Subsystem 1 - Part No SW: 8K0 959 339 B HW: 8K0 959 339 B
Component: BF-Gewichtss. H01 0030
Serial number: 5810000R0800001SGN

Crash sensor for side airbag: driver side:
Serial number: 6334MSME3F333805D

Crash sensor for side airbag: front passenger side:
Serial number: 6344MSME3F31082EK

Crash sensor for side airbag: rear: driver side:
Serial number: 6352QSME5D0A1738O

Crash sensor for side airbag: rear: passenger side:
Serial number: 6362QSME0D0F2716M

Crash sensor for front airbag: driver side:
Serial number: 63732SME0E093818%

Crash sensor for front airbag: front passenger side:
Serial number: 63832SME4A0C3330Z

No fault code found.

-------------------------------------------------------------------------------
Address 16: Steering wheel (J527) Labels:. 8K0-953-568.clb
Part No SW: 8K0 953 568 F HW: 8K0 953 568 F
Component: Lenks.Modul H13 0013
Revision: -------- Serial number: 90315HI80006S
Coding: 000014
Shop #: WSC 02399 823 56573
VCID: 3D27C5793D7EB77FE23-8068

Component: E221 - MFL H02 0003

No fault code found.

-------------------------------------------------------------------------------
Address 17: Instruments (J285) Labels:. 8T0-920-xxx-17.clb
Part No SW: 8K0 920 950 A HW: 8K0 920 950 A
Component: KOMBIINSTR. H17 0224
Revision: 00000000 Serial number: 9DR11P898
Coding: 8B1209000300D705020000
Shop #: WSC 02399 823 56573
VCID: 2D07F539ED1E27FF523-8078

1 Fault Found:
00532 - Supply Voltage B+
002 - Lower Limit Exceeded - Intermittent
Freeze Frame:
Fault Status: 00100010
Fault Priority: 4
Fault Frequency: 1
Reset counter: 55
Mileage: 215938 km
Time Indication: 0
Date: 2008.05.28
Time: 23:27:45


-------------------------------------------------------------------------------
Address 19: CAN Gateway (J533) Labels:. 8T0-907-468.clb
Part No SW: 8T0 907 468 H HW: 8T0 907 468 H
Component: GW-BEM 5CAN H06 0094
Revision: 4GB20042 Serial number: 4200G088218307
Coding: 000303
Shop #: WSC 02399 823 56573
VCID: 46D5AA9568A8F4A7B39-8012

1 Fault Found:
02071 - Local Databus
012 - Electrical Fault in Circuit
Freeze Frame:
Fault Status: 01101100
Fault Priority: 2
Fault Frequency: 1
Reset counter: 15
Mileage: 215954 km
Time Indication: 0
Date: 2008.05.27
Time: 00:27:58


-------------------------------------------------------------------------------
Address 2E: Media Player 3 (R199) Labels:. 8T0-035-785.clb
Part No SW: 8T0 035 785 HW: 8T0 035 785
Component: SG ext.Player H06 0210
Revision: 00000000
Coding: 020302
Shop #: WSC 02399 823 56573
VCID: 78A9146D52DC5257F15-802C

No fault code found.

-------------------------------------------------------------------------------
Address 42: Door Elect, Driver (J386) Labels:. 8K0-959-793.clb
Part No SW: 8K0 959 793 D HW: 8K0 959 793 D
Component: TSG FA H11 0250
Revision: Serial number: 0000007644714
Coding: 011C03204000410001
Shop #: WSC 02399 823 56573
VCID: 41DFB9894186D39F86B-8014

No fault code found.

-------------------------------------------------------------------------------
Address 46: Central Conv. (J393) Labels:. 8K0-907-064-46.clb
Part No SW: 8K0 907 064 F HW: 8K0 907 064 F
Component: BCM2 1.1 H80 0141
Revision: 00002001 Serial number: 0113959993
Coding: 0106023A007A400400B001
Shop #: WSC 02399 823 56573
VCID: 3333E3410B3A710F047-8066

Subsystem 1 - Part No SW: 8K0 959 719 HW: 8K0 959 719
Component: GTO BF H06 0040
Serial number: 00000000000000069985

Subsystem 2 - Part No: 1K0 951 605 C
Component: LIN BACKUP HO H03 1301

Subsystem 3 - Part No SW: 8K0 959 591 A HW: 8K0 959 591
Component: J245 PS045 H07 0041

1 Fault Found:
00926 - Terminal 30
011 - Open Circuit
Freeze Frame:
Fault Status: 01101011
Fault Priority: 2
Fault Frequency: 1
Reset counter: 15
Mileage: 215954 km
Time Indication: 0
Date: 2008.05.27
Time: 00:28:00


-------------------------------------------------------------------------------
Address 47: Sound System (J525) Labels:. 8T0-035-223-ASC.clb
Part No SW: 8T0 035 223 AB HW: 8T0 035 223
Component: DSP STD H07 0220
Revision: S2100000
Coding: 0203010102
Shop #: WSC 02399 823 56573
VCID: 6E85323520981CE72B9-803A

No fault code found.

-------------------------------------------------------------------------------
Address 52: Door Elect, Pass. (J387) Labels:. 8K0-959-792.clb
Part No SW: 8K0 959 792 D HW: 8K0 959 792 D
Component: TSG BF H11 0250
Revision: Serial number: 0000007651469
Coding: 011C03204000410001
Shop #: WSC 02399 823 56573
VCID: 40D9BC8D4A8CDA97895-8014

No fault code found.

-------------------------------------------------------------------------------
Address 53: Parking Brake (J540) Labels: 8K0-907-801-V1.clb
Part No SW: 8K0 907 801 E HW: 8K0 907 801 E
Component: EPB Audi B8 H05 0060
Revision: 00000003 Serial number: 00000000212122
Shop #: WSC 00000 000 00000
VCID: 313FE949F126431F76B-8064

No fault code found.

-------------------------------------------------------------------------------
Address 56: Radio (J503) Labels:. 8Tx-035-1xx-56.clb
Part No SW: 8T1 035 195 L HW: 8T1 035 195 L
Component: Symph3 Sirius H02 0211
Revision: 00000004 Serial number: AUZ5Z4H1041784
Coding: 04020002010185004119070800
Shop #: WSC 02399 823 56573
VCID: 40D9BC8D4A8CDA97895-8014

Subsystem 1 - Part No SW: 8T0 919 603 A HW: 8T0 919 603 A
Component: Display

1 Fault Found:
02635 - Tuner Not Enabled/Activated
000 - -
Freeze Frame:
Fault Status: 01100000
Fault Priority: 7
Fault Frequency: 1
Reset counter: 15
Mileage: 215954 km
Time Indication: 0
Date: 2008.05.27
Time: 00:28:08

[mtroxel]

Seems like your test pulling the alternator out of the circuit tells the tale.

This is only the 459th time I've heard of someone buying a bad alternator from an O'Reilly/Pep Boys/AutoZone, then they take it back and get a replacement crap alternator that's equally diseased.

[Jimmyhummus]

Thanks for the quick feedback Mtroxel. That’s all I’ve read too was second hand alternators being the culprit but read so many other times there were no issues. My question is the first one had issues when testing the diode but the current one passes but provide the same result. The alternator is a reman Bosch and I’m assuming the specs are not the same as Audi’s which is resulting In the high drain - but why? Is there a relay that may be bad that’s switched on leaving 500 mA causing the drain?

I ended up buying an OEM alternator just to remove that variable and will post Back once I get it installed. Until then any other ideas?

When checking the voltage at the d pin I’m getting 11.5V. Does that sound right Or should it be 0?

[mtroxel]

When checking the voltage at the d pin I’m getting 11.5V. Does that sound right Or should it be 0?

Not sure what you mean by the D pin. Isn't there a D+ and a D- on an alternator? Tell me where you're testing and I'll go out and tell you what a healthy elec system reads...if I don't have to take apart too much stuff to get there.

[Jimmyhummus]

Sorry this is the wire/plug coming in that looks like a “D”; I believe the exciter. The opposite of the B+

[Smac770]

We've been through this with another person getting the wrong PepBoys reman (wrong voltage regulator) and having all kinds of problems. Just don't do it. Or if you do, you'll have to be better than the seller at knowing if it's the correct product.
What are the actual Bosch style part numbers on the voltage regulator and alternator? 2009, are you sure they didn't give you the one for the B7 BWT motor (in the '09 cabriolet, but irrelevant to the sedan/avant).

That's the LIN bus connection between the car and the voltage regulator, designated COM. It's a 2-position plug, but only 1 pin/wire installed on our cars. The only other connection on our alternators is the "B+" post and the "GND" via the housing.
Be careful assuming old mechanisms with modern devices. LIN is a comms bus; you need a LIN aware logic analyzer to make much sense of it.

[Jimmyhummus]

Thanks Smac for the LIN bus clarification. I attempted to find some type of part number onthe voltage regulator or alternator and only found the pepboys Pn (23255) which per the website fits the 09 Audi A4 140 amp Bosch reman. It does however also say cabriolet.

[Smac770]

09 A4 CABRIOLET IS B7, BWT engine. Wrong alternator.

[Jimmyhummus]

That’s interesting how it shows up as compatible on their website. Should have double checked and not assumed.

Question though - is voltage continually supplied through the LIN bus(2 pin plug)? Or is there a relay prior to the voltage regulator?

[Smac770]

It's a digital comms line, not a power line or analog control line. It's constantly bouncing 0v/12v, thus you need an o-scope to see the signaling and a logic analyzer to interpret the signaling. Multimeter isn't really useful.

[Smac770]

"That’s interesting how it shows up as compatible on their website." It is compatible, with the 2009 A4 2.0T cabriolet. But not the 2009 A4 2.0T sedan or 2009 A4 2.0T avant. Thus why it notes cabriolet in the fitment notes. But yes, I'd say their database people are substandard for not knowing to ask sedan/avant vs cabriolet so they display only actually compatible parts. Thus why I often also check for 2010, which has no such overlap, to see what shows up when looking at engine parts. But then you have places like FCPEuro who do ask, but then still shows parts for both the CAEB and BWT. But such is the world.

[Jimmyhummus]

Thanks Smac. Huge helping in figuring that piece out. The alternator is in route and will Ben here 2/25 and will test then. I did some googling but couldn’t find a difference in the alternator between the B7 and B8 that would result in a large battery draw. DO you think there’s something in the B8 alternator that has a relay of some sort or a way to compensate for the 500-600 mA draw? I’ll update the thread after replacement of the alternator. Any insight into the difference between would be interesting to read up on. Thanks.

[Smac770]

We've been down this road in this forum before.
https://www.audizine.com/forum/showt...1#post13857786

For a B8.0 A4 CAEB with Bosch 140A alternator, the proper product is Audi 06H 903 016 L aka Bosch AL891N, which has a plug type 464, which has a LIN bus COM pin for alternator management by the J519.
For a B7 A4 2.0T, Bosch shows a variety of new and reman product numbers, but they all have plug type 367, same as the alternator for an 8P A3, as discussed in the link thread.

So very different management of the voltage regulator, and there's no value in guessing why using a completely wrong VR would result in unexpected results.

[Danzzo]

We've been down this road in this forum before.
https://www.audizine.com/forum/showt...1#post13857786

For a B8.0 A4 CAEB with Bosch 140A alternator, the proper product is Audi 06H 903 016 L aka Bosch AL891N, which has a plug type 464, which has a LIN bus COM pin for alternator management by the J519.
For a B7 A4 2.0T, Bosch shows a variety of new and reman product numbers, but they all have plug type 367, same as the alternator for an 8P A3, as discussed in the link thread.

So very different management of the voltage regulator, and there's no value in guessing why using a completely wrong VR would result in unexpected results.

I'm the OP from that thread! I went with FCP Euro next day shipping for my alternator. TRUST ME, GET AN OEM Alternator (From FCP EUro if you can, these guys will set you right!)

Don't be like me and learn from my thread. Never get aftermarket electronics for Audi's.

[Jimmyhummus]

Sorry fellas. Definitely did not plan to reinvent the wheel. All my searches unfortunate didn’t cross hat thread. A lot of good info in that one.

[Smac770]

No problems. I just didn't want to have to retype all that stuff. :-)

But yeah, anytime you're looking at '09 parts, if it says anything about the cabriolet, it's not for our car.

[Jimmyhummus]

Thanks all - got the OEM alternator in and battery draw has subsided I think. Doing the ultimate test of just letting it sit for two days to confirm nothing else weird is happening. The draw on the battery is around 30 mA so definitely within spec. At the end of the day OEM is preferred with a replacement alternator.

The weird thing is that after clearing the codes I figured all would be ok. Two were cleared however the B+ and terminal 30 is still there.

New codes are below. Any ideas? Couple things to note my trunk does not open with the release on the trunk or the switch from the drivers side door. And the auto down function doesn’t work on drivers side window just for the driver window, rest work ok. I was going to look into these next after getting the car driveable as these are creature features I can deal with so as long as the car is driveable.

Address 46: Central Conv. (J393) Labels:. 8K0-907-064-46.clb
Part No SW: 8K0 907 064 F HW: 8K0 907 064 F
Component: BCM2 1.1 H80 0141
Revision: 00002001 Serial number: 0113959993
Coding: 0106023A007A400400B001
Shop #: WSC 02399 823 56573
VCID: 3333E3410B3A710F047-8066

Subsystem 1 - Part No SW: 8K0 959 719 HW: 8K0 959 719
Component: GTO BF H06 0040
Serial number: 00000000000000069985

Subsystem 2 - Part No: 1K0 951 605 C
Component: LIN BACKUP HO H03 1301

Subsystem 3 - Part No SW: 8K0 959 591 A HW: 8K0 959 591
Component: J245 PS045 H07 0041

1 Fault Found:
00926 - Terminal 30
011 - Open Circuit
Freeze Frame:
Fault Status: 01101011
Fault Priority: 2
Fault Frequency: 1
Reset counter: 16
Mileage: 215954 km
Time Indication: 0
Date: 2008.05.27
Time: 17:04:01


Address 17: Instruments (J285) Labels:. 8T0-920-xxx-17.clb
Part No SW: 8K0 920 950 A HW: 8K0 920 950 A
Component: KOMBIINSTR. H17 0224
Revision: 00000000 Serial number: 9DR11P898
Coding: 8B1209000300D705020000
Shop #: WSC 02399 823 56573
VCID: 2D07F539ED1E27FF523-8078

1 Fault Found:
00532 - Supply Voltage B+
002 - Lower Limit Exceeded - Intermittent
Freeze Frame:
Fault Status: 00100010
Fault Priority: 4
Fault Frequency: 1
Reset counter: 55
Mileage: 215938 km
Time Indication: 0
Date: 2008.05.28
Time: 23:27:45

[Smac770]

The auto-up/down always has to be reinitialized after a battery replacement. Just one of those industry things for whatever reason. Procedure should be in your owner's manual. I know it's been discussed here in at least one thread in the past year, too.

As for the DTCs, they seem reasonable enough.

J393 aka BCM2, which sits in the right rear with all the fuse rows, is saying one of the term 30 supplies is not supplying 12v. So check fuses and plugs. The J393 gets several 12v supplies as it powers the rear lamps. Looks like the fuses of interest would be that fuse panel F (right rear fuse blocks), row 2 (you'll see a B on it, but those are rows, not "panels"), fuses 8, 10, and 11.

As for the trunk release, I suspect that's related to your J393 fuse issue. The V53 lock/unlock motor for the trunk is driven by the J393. If the source 12v for that circuit is not powered, then it can't actuate the lock motor.

Instrument cluster, it has a single 32-pin plug, with pins 31 and 32 both being connected to fuse panel D (the right end of the dash), row 2 (middle), either fuse 5 (through Apr '09) or fuse 4 (from May '09). Maybe the fuse is flaky, maybe the plug connection is flaky, who knows. I'd just run things as is for a few days, then check and clear DTCs again, see what's what.

[Jimmyhummus]

Hi All - figured I would update as part of the items related to this thread. The OEM alternator arrived and fixed the draw issue! All good. Also tested over a couple days and no deadline battery - wifey is super excited to not be stranded.

The window fix was pretty easy, thanks for reminding me on that piece. It’s now just the boot latch that won’t open with the Key button or the trunk button. There’s no place to manually insert a key so I have to pull the back seat down and reach around the. pull the safety latch in the trunk .

Thanks for the recommendation for the J393 and the fuses however nothing looked odd and no fuses blown. I ended up buying a new boot latch thinking it was the actuator since it was relatively cheap, however after replacement of the latch there was no change.

To your point Smac, with my B8, I only have fuses on the B panel on numbers 1, 5, 7, 8, 10, 12 - all look fine.

Any other thoughts would be greatly appreciated.

[Jimmyhummus]

[IMG][url=https://www.audizine.com/gallery/showphoto.php?ph[/IMG]

picture of the boot fuses. I also noticed there is a "blue wire" just hanging there not connected

[Jimmyhummus]

https://www.audizine.com/gallery/sho...fuses&cat=500][/url][/IMG]

[Smac770]

And there's your problem. That yellow 20 in row 2/B is in position 12, not position 11 where it belongs. A fuse in that position 12 would have only be a 5A if there should have been a fuse there.
I have no idea what that two wire blade is suppose to attach; I cannot see anything equivalent in that area on my car.

[Jimmyhummus]

Smac!!!!!! Huge help. I can’t believe that happened. Thinking back I sent my Audi in initially due to the drain issue I had and they mentioned it would take a lot of hours to figure it out and would make more sense for me to rule out some issues first. That being said they must have pulled some fuses and didn’t put them back in the right location. I only know this because I took a picture of the fuses in each panel before I started checking and pulling them. So that fixed the issue with the key and driver side release. But now the boot release button doesn’t work. At this point I put the original latch back in and does the same as the new one so I’m keeping the original one installed and will have the other just as a backup. The new one also doesn’t make a difference in the boot release button. I imagine the boot release button is on the same fuse so if the rest are working the fuse should be fine.

I did my best to check around for where that blue wire may fit but can’t see anything. Also did a bunch of google searches and nothing. There’s no after market install and my original picture before pulling fuses wasn’t zoomed out to see if maybe the dealership pulled and didn’t put everything back together. No idea on that one.

Smac can’t say enough for the help and would love to shoot something your way for all the love. I’ll shoot you a PM and go from there. Thanks again.

Jimmyhummus!

[Smac770]

The fuse is for the power to the J393, which the J393 uses to activate the lock motor. So no input trigger was going to release that lid while the lock was essentially unpowered. Now you're powered, but only two of the three input triggers appear to function. So looking at why the lid mounted release button doesn't work is actually a completely different set of concerns than what got us to the fuse.

The lid mounted release button, F248, is just two wires. One comes from the J393 (the same module that manages your tail lights and the lid release motor and your remote access, etc) and the other goes to ground, the same ground as the license plate bulbs (are your license plate bulbs working?). I have a wagon, so I don't know anything about how the button is located or accessed in a sedan. If you really wanted to trace it, you'd pull the T32d plug off the J393, connect one probe of a multimeter to pin 3, the other probe to ground (the circuit uses the one there near the J393, the bolt with the brown wires on it), then test for continuity as you press the button. Pressing it should close the circuit and the multimeter should report continuity and very low resistance.

But another thread that points out apparently one can disable the rear lid button: https://www.audizine.com/forum/showt...t-release-work

I do not think that wire would be related to this concern. I have no idea what it might be for. The wiring diagram does not show a single plug with just two wires, of one blue and one gray/blue.