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Discussion Starter · #1 ·
Ok so odd situation, curious if anyone has any ideas that would help me as me and my cars circle of trust has been broken for the moment.

Car showed no issues, parked, went back to the car after 30m or so and the door unlocked fine, sit in the driver seat, hit the start button and nada, ignition won’t power up, attempt, blink or anything. It was as if I didn’t have the keys with me.

I got my spare key, repeated attempt, same result.

I bought new batteries for both keys, same result.

I had to leave the vehicle where it was overnight, figured it must be the battery. So the next day I try again, nothing same result. Overall I must have hit that start button 30 times at minimum. Guy shows up to jump me, has his head in the hood says try one last time before he connects the jumper and she started w/o hesitation. (Figures right?)

So i go to get the battery tested, battery still showed strong, alternator as well. Car has been fine for the last 24 hours now, starting multiple times.

I scan w/odbeleven and get this code. Any thoughts? Could it still be a battery issue maybe? This code was dated 18 days before I was stranded.

Thanks guys! I love my car and don’t want to fear being stuck at any time.

09 Central Electrics

System description: BCM MQBAB HNA
Software number: 5Q0937085AJ
Software version: 0175
Hardware number: 5Q0937085AF
Hardware version: H24
Serial number: 01061527500224
ODX name: EV_BCMMQB
ODX version: 015001
Long coding: 00011B46C041A2E169E44000091C07201800000000000000000000000000

Subsystems:
System description: WWS 150929
Software version: 0551
Hardware version: 043
Serial number: 151009213810
Long coding: 0E4DDD

System description: RLHS
Software version: 0059
Hardware version: 037
Serial number: S4Y15M10D21H16M37S16
Long coding: 90A8DD

Trouble codes:
U112100 - Databus missing message
Intermittent
Date: 2021-08-30 19:26:03
Mileage: 119862 km
Priority: 6
Malfunction frequency counter: 2
Unlearning counter: 97
Terminal 15 status: On
Terminal 50 status: Off
Voltage: 13.8 V
Outside air temperature: 25.5 °C
Status Bremslichtschalter (HW): Off
Status Bremslichtschalter (CAN): Off
Off: not activated
Parking light: not activated
Automatic high beam assist: operated
Low beam: not activated
Parking light left: not activated
Parking light right: not activated
Letzte Weckursache/ Werte [00;2E]: Pin A32 Heckdeckel Softtouch TasterPin
CAN-Bus_aktiv: On
 

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Discussion Starter · #3 ·
Battery terminals oxidized, Poor contact ?


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Battery was replaced by vw 2-3 yrs ago. Terminals still look new. Good thought though. I might still change the battery to play it safe.
 

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Seems like it didn’t have power, check the ground cable from the battery to the body


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2016 Golf R, 2001 Cabrio VR6
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Ok so odd situation, curious if anyone has any ideas that would help me as me and my cars circle of trust has been broken for the moment.

Car showed no issues, parked, went back to the car after 30m or so and the door unlocked fine, sit in the driver seat, hit the start button and nada, ignition won’t power up, attempt, blink or anything. It was as if I didn’t have the keys with me.

I got my spare key, repeated attempt, same result.

I bought new batteries for both keys, same result.

I had to leave the vehicle where it was overnight, figured it must be the battery. So the next day I try again, nothing same result. Overall I must have hit that start button 30 times at minimum. Guy shows up to jump me, has his head in the hood says try one last time before he connects the jumper and she started w/o hesitation. (Figures right?)

So i go to get the battery tested, battery still showed strong, alternator as well. Car has been fine for the last 24 hours now, starting multiple times.

I scan w/odbeleven and get this code. Any thoughts? Could it still be a battery issue maybe? This code was dated 18 days before I was stranded.

Thanks guys! I love my car and don’t want to fear being stuck at any time.

09 Central Electrics

System description: BCM MQBAB HNA
Software number: 5Q0937085AJ
Software version: 0175
Hardware number: 5Q0937085AF
Hardware version: H24
Serial number: 01061527500224
ODX name: EV_BCMMQB
ODX version: 015001
Long coding: 00011B46C041A2E169E44000091C07201800000000000000000000000000

Subsystems:
System description: WWS 150929
Software version: 0551
Hardware version: 043
Serial number: 151009213810
Long coding: 0E4DDD

System description: RLHS
Software version: 0059
Hardware version: 037
Serial number: S4Y15M10D21H16M37S16
Long coding: 90A8DD

Trouble codes:
U112100 - Databus missing message
Intermittent
Date: 2021-08-30 19:26:03
Mileage: 119862 km
Priority: 6
Malfunction frequency counter: 2
Unlearning counter: 97
Terminal 15 status: On
Terminal 50 status: Off
Voltage: 13.8 V
Outside air temperature: 25.5 °C
Status Bremslichtschalter (HW): Off
Status Bremslichtschalter (CAN): Off
Off: not activated
Parking light: not activated
Automatic high beam assist: operated
Low beam: not activated
Parking light left: not activated
Parking light right: not activated
Letzte Weckursache/ Werte [00;2E]: Pin A32 Heckdeckel Softtouch TasterPin
CAN-Bus_aktiv: On
I don't think this fault code has anything to do with your battery voltage, although your no start condition could feasibly.
I am no VCDS expert (how I wish I were) but let us look at what this is telling us. Maybe I am interpreting this wrong; if a Ross-Tech pro can correct me, I would appreciate it.

Malfunction frequency counter: 2
Unlearning counter: 97

The code has appeared twice, and the unlearning counter is how many more cycles (starts I assume) are required to clear the code. It can start at different numbers for different issues, but I assume it started at 100.

Terminal 15 status: On
Terminal 50 status: Off

Terminal 15 is the connection to the battery when ignition is switched on, as in the car is running. Terminal 50 is the connection to the battery when cranking, e.g., the starter.

Voltage: 13.8 V
This is very healthy system voltage, at least it tells you that the alternator was functional on this day.

Letzte Weckursache/ Werte [00;2E]: Pin A32 Heckdeckel Softtouch TasterPin
From Google translate:
Last alarm cause / values [00; 2E]: Pin A32 trunk lid soft touch button pin
So I googled this phrase and it comes up on two other MQB cars with totally unrelated problems (a TT with a steering issue and a Skoda with a lighting issue). My guess is it is a random electrical problem associated with power or ground issues.

But I am a bored idiot with access to the wiring diagrams for this model. So, what is pin A32? Well, first I think, "there are not many connectors on this car with 32 or more pins..." As a shot in the dark, I started looking at the connector descriptions for everything with at least 32 pins that is possibly related to "trunk lid soft touch button pin." Here is T73a:
Font Line Material property Parallel Rectangle

Pin 32 - Rear lid handle release button -E234-
Some other interesting things in this connector:
Pin 13 - Terminal 15 voltage supply relay -J329-
Pin 44 - Ignition/starter switch -D- , terminal 15
Pin 47 - Ignition/starter switch -D- , terminal 15
There are also pins here related to the steering column ECU and many lighting functions. So my hair brain theory is that a bad ground in this connector maybe caused those issues I mentioned with the other MQB cars earlier, and maybe caused your issue as well.
This connector is grounded (terminal 31) in two pins:
Pin 12 - Terminal 31
Pin 63 - Terminal 31
Rectangle Parallel Font Diagram Slope

I believe T73a is one of these connectors. It will be black in color.
Font Rectangle Art Urban design Painting

Both pins 63 and 12 on T73a are ground bridges (279 and 286) in the interior wiring harness (5 and 8 respectively). This means there is a connection within the wiring harness in which a load of other things are grounded. Both of these wires ultimately ground at 44 on the left A-pillar.
Map Slope Font Parallel Engineering


My next step would be to check for continuity to ground on pins 12 and 63 on connector T73a. You could do this directly at that connector, or possibly at the start button, or even the rear hatch release button that caused the fault code.
Font Parallel Rectangle Engineering Screenshot

Slope Rectangle Font Parallel Diagram

Before you do any of that, I would do as others have suggested and check the battery is grounded to the chassis properly.
Good luck.
 

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I don't think this fault code has anything to do with your battery voltage, although your no start condition could feasibly.
I am no VCDS expert (how I wish I were) but let us look at what this is telling us. Maybe I am interpreting this wrong; if a Ross-Tech pro can correct me, I would appreciate it.

Malfunction frequency counter: 2
Unlearning counter: 97

The code has appeared twice, and the unlearning counter is how many more cycles (starts I assume) are required to clear the code. It can start at different numbers for different issues, but I assume it started at 100.

Terminal 15 status: On
Terminal 50 status: Off

Terminal 15 is the connection to the battery when ignition is switched on, as in the car is running. Terminal 50 is the connection to the battery when cranking, e.g., the starter.

Voltage: 13.8 V
This is very healthy system voltage, at least it tells you that the alternator was functional on this day.

Letzte Weckursache/ Werte [00;2E]: Pin A32 Heckdeckel Softtouch TasterPin
From Google translate:
Last alarm cause / values [00; 2E]: Pin A32 trunk lid soft touch button pin
So I googled this phrase and it comes up on two other MQB cars with totally unrelated problems (a TT with a steering issue and a Skoda with a lighting issue). My guess is it is a random electrical problem associated with power or ground issues.

But I am a bored idiot with access to the wiring diagrams for this model. So, what is pin A32? Well, first I think, "there are not many connectors on this car with 32 or more pins..." As a shot in the dark, I started looking at the connector descriptions for everything with at least 32 pins that is possibly related to "trunk lid soft touch button pin." Here is T73a:
View attachment 117774
Pin 32 - Rear lid handle release button -E234-
Some other interesting things in this connector:
Pin 13 - Terminal 15 voltage supply relay -J329-
Pin 44 - Ignition/starter switch -D- , terminal 15
Pin 47 - Ignition/starter switch -D- , terminal 15
There are also pins here related to the steering column ECU and many lighting functions. So my hair brain theory is that a bad ground in this connector maybe caused those issues I mentioned with the other MQB cars earlier, and maybe caused your issue as well.
This connector is grounded (terminal 31) in two pins:
Pin 12 - Terminal 31
Pin 63 - Terminal 31
View attachment 117777
I believe T73a is one of these connectors. It will be black in color.
View attachment 117778
Both pins 63 and 12 on T73a are ground bridges (279 and 286) in the interior wiring harness (5 and 8 respectively). This means there is a connection within the wiring harness in which a load of other things are grounded. Both of these wires ultimately ground at 44 on the left A-pillar.
View attachment 117779

My next step would be to check for continuity to ground on pins 12 and 63 on connector T73a. You could do this directly at that connector, or possibly at the start button, or even the rear hatch release button that caused the fault code.
View attachment 117782
View attachment 117783
Before you do any of that, I would do as others have suggested and check the battery is grounded to the chassis properly.
Good luck.
Great logical problem solving.
I too am no expert but this seems spot on.
I would probably go straight to finding a ground fault too.

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Car showed no issues, parked, went back to the car after 30m or so and the door unlocked fine, sit in the driver seat, hit the start button and nada, ignition won’t power up, attempt, blink or anything. It was as if I didn’t have the keys with me.
I had, perhaps, a related issue with my 2019. The start/stop button would activate the accessories/whatever, but the display showed "No Key recognized" when I tried to start the car. I most certainly had the keys on me, with new batteries.

I finally got things going after I locked/alarmed the car with the remote, and then unlocked it. Previously, I'd only locked and unlocked the car via the proximity sensors. How do you unlock your car? I know it's probably not this, but could it be a similar issue?
 

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My battery took a **** randomly, tried to go out on lunch at work. had 2v before a jump, showed healthy after. Car was undriveable voltage was jumping all over the place, thought maybe i killed alternator, caused my gauges to jump around speakers to pop when driving.

Parked it and got a new battery and problem was fixed. Suspect cell died.
 

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My previous vehicle, a '10 Mazda5, developed a phantom electrical drain somewhere. The first time it stranded me, I just assumed the battery had expired so I replaced it. Several weeks later it happened again: parked the car and an hour later came out to find it completely dead - not even a clicking noise. Took it to the dealer and they happily racked up $250 worth of "diagnostic" time only to find nothing.

The car would work fine for weeks on end, then randomly strand me someplace. That got old real fast, so I traded it in when I bought my R.

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Discussion Starter · #13 ·
I don't think this fault code has anything to do with your battery voltage, although your no start condition could feasibly.
I am no VCDS expert (how I wish I were) but let us look at what this is telling us. Maybe I am interpreting this wrong; if a Ross-Tech pro can correct me, I would appreciate it.

Malfunction frequency counter: 2
Unlearning counter: 97

The code has appeared twice, and the unlearning counter is how many more cycles (starts I assume) are required to clear the code. It can start at different numbers for different issues, but I assume it started at 100.

Terminal 15 status: On
Terminal 50 status: Off

Terminal 15 is the connection to the battery when ignition is switched on, as in the car is running. Terminal 50 is the connection to the battery when cranking, e.g., the starter.

Voltage: 13.8 V
This is very healthy system voltage, at least it tells you that the alternator was functional on this day.

Letzte Weckursache/ Werte [00;2E]: Pin A32 Heckdeckel Softtouch TasterPin
From Google translate:
Last alarm cause / values [00; 2E]: Pin A32 trunk lid soft touch button pin
So I googled this phrase and it comes up on two other MQB cars with totally unrelated problems (a TT with a steering issue and a Skoda with a lighting issue). My guess is it is a random electrical problem associated with power or ground issues.

But I am a bored idiot with access to the wiring diagrams for this model. So, what is pin A32? Well, first I think, "there are not many connectors on this car with 32 or more pins..." As a shot in the dark, I started looking at the connector descriptions for everything with at least 32 pins that is possibly related to "trunk lid soft touch button pin." Here is T73a:
View attachment 117774
Pin 32 - Rear lid handle release button -E234-
Some other interesting things in this connector:
Pin 13 - Terminal 15 voltage supply relay -J329-
Pin 44 - Ignition/starter switch -D- , terminal 15
Pin 47 - Ignition/starter switch -D- , terminal 15
There are also pins here related to the steering column ECU and many lighting functions. So my hair brain theory is that a bad ground in this connector maybe caused those issues I mentioned with the other MQB cars earlier, and maybe caused your issue as well.
This connector is grounded (terminal 31) in two pins:
Pin 12 - Terminal 31
Pin 63 - Terminal 31
View attachment 117777
I believe T73a is one of these connectors. It will be black in color.
View attachment 117778
Both pins 63 and 12 on T73a are ground bridges (279 and 286) in the interior wiring harness (5 and 8 respectively). This means there is a connection within the wiring harness in which a load of other things are grounded. Both of these wires ultimately ground at 44 on the left A-pillar.
View attachment 117779

My next step would be to check for continuity to ground on pins 12 and 63 on connector T73a. You could do this directly at that connector, or possibly at the start button, or even the rear hatch release button that caused the fault code.
View attachment 117782
View attachment 117783
Before you do any of that, I would do as others have suggested and check the battery is grounded to the chassis properly.
Good luck.
Wow thanks so much for the time to go through that. It maybe over my head but I’ll try to find the grounds and double check them. Odd thing, i was sitting in the back w/the hatch open before it worked I closed hatch and it did fire up.
 

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Discussion Starter · #14 ·
I had, perhaps, a related issue with my 2019. The start/stop button would activate the accessories/whatever, but the display showed "No Key recognized" when I tried to start the car. I most certainly had the keys on me, with new batteries.

I finally got things going after I locked/alarmed the car with the remote, and then unlocked it. Previously, I'd only locked and unlocked the car via the proximity sensors. How do you unlock your car? I know it's probably not this, but could it be a similar issue?
Yeah I hit the lock unlock a bunch, didn’t seem to have any affect. I don’t usually hit the handle though, something to think about if it happens again.
 
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