C7 A6 Allroad - LED Reverse Lamp retrofit - Coding problem

nugentp · Jul 19, 2020

So I fitted some OSRAM LED replacements for the rubbish yellow W16W reverse lamps in the C7 wagon.
They are sold as the usual 'CANBus error free' nonsense but of course they give nag alarms in the dashboard.

I went into Central Electrics looking to deactivate load monitoring - strangely there are no options visible to disable this for the reverse lamps, but there are TWO entries for Turn Signals (both for cold monitoring & load monitoring - maybe they are dual for front and rear) so I hopes it was a typo and disabled ALL forms of lamp monitoring - saved that, accepted, power cycled - still get nag alarms.

Coding below from BEFORE attempting to make any changes. I set BYTES 13 and 14 to 0x00 and it made no impact.

Code:

Address 09: Cent. Elect. (J519)       Labels:. 4H0-907-063-V1.clb
   Part No SW: 4H0 907 063 BP    HW: 4H0 907 063 
   Component: BCM1 2.0      H12 0111  
   Revision: 11012002    Serial number: 00000001287572
   Coding: 260020118034A7E00905008300001D0CCF9DC70827080101000008402100
   Shop #: WSC 50290 003 104857
   VCID: F7BE6F7046B5E03EBA-80A3

   Subsystem 1 - Part No SW: 4G2 955 119     HW: 4G8 955 119 A  Labels: 1KX-955-119.CLB
   Component: WWS57X 120309  H35 0080 
   Serial number:         120317110929
   Coding: 0045F7

   Subsystem 2 - Part No SW: 8K0 955 559     HW: 8K0 955 559   Labels: 8K0-955-559.CLB
   Component: RLS  H04 0003 
   Serial number: 20139503            
   Coding: 02512B

   Subsystem 3 - Part No SW: 4G0 941 531     HW: 4G0 941 531 
   Component: E1 - LDS  H07 0044 
   Serial number: 04 04 2012  00000812

   Subsystem 4 - Part No SW: 4H0 907 658     HW: 4H0 907 658 
   Component: AQ_Hum_Sensor  H03 0003 
   Serial number: E9A80326000000000001

No fault code found.

If anyone knows the magic trick for disabling this annoying feature on the car it would be nice as the OSRAM LED reverse lights are a vast improvement over the 19th century OE bulbs.

Uwe · Jul 19, 2020

Aren't the lights on the tail end of that car controlled by 46 BCM2?

-Uwe-

nugentp · Jul 20, 2020

Thats news to me sir, but I will certainly have a look there.

nugentp · Jul 20, 2020

Code:

Monday,20,July,2020,13:38:38:30756
VCDS Version Release 20.4.1 Running on Windows 7 x86(Parallels)
www.Ross-Tech.com

                Address 46: Central Conv.       Labels: 4H0-907-064-46.clb
Control Module Part Number: 4H0 907 064 FG    HW: 4H0 907 064 BG
  Component and/or Version: BCM2 2.0      H31 0560
           Software Coding: 013F062220B9040083200904000104000000000000000000000000000000
            Work Shop Code: WSC 50290 003 104857
                      VCID: F3A65B6052CD8C1E86-80A7
2 Faults Found:

01519 - Bulb for Back-Up Lights; Right (M17) 
            012 - Electrical Fault in Circuit - MIL ON
             Freeze Frame:
                    Fault Status: 11101100
                    Fault Priority: 2
                    Fault Frequency: 1
                    Reset counter: 94
                    Mileage: 164945 km
                    Time Indication: 0
                    Date: 2020.07.20
                    Time: 13:37:15

01518 - Bulb for Back-Up Lights; Left (M16) 
            012 - Electrical Fault in Circuit - MIL ON
             Freeze Frame:
                    Fault Status: 11101100
                    Fault Priority: 2
                    Fault Frequency: 1
                    Reset counter: 94
                    Mileage: 164945 km
                    Time Indication: 0
                    Date: 2020.07.20
                    Time: 13:37:15

So for sure controller 46 is the one with nag alarms active, but unfortunately its only partially documented and I cannot see any coding bits or bytes for the reverse lamp monitoring. Maybe the controller is better documented in German or from another family variant ???

nugentp · Jul 20, 2020

Wondering is it worth reading some adaptation channels with and without the reverse lights fitted to see if I can spot any differences - any suggestions for some target range of channel numbers would be very welcome though.

nugentp · Jul 20, 2020

So - did some more background reading and then noted all of the adaptation values in channels 197 - 255 (some of those are not available but vast majority are OK). I took readings with OE reverse bulbs fitted and again with bulbs removed - no differences detected in any of those ~50 bytes. What am I doing wrong here ?

Uwe · Jul 20, 2020

I just looked through the German label file for BCM2 and don't see anything obvious in there that can be used to tell the module that those bulbs are now LEDs.

-Uwe-

nugentp · Jul 20, 2020

Dangit - why is the C7 such a stupid/cursed/undocumented platform ?

nugentp · Jul 20, 2020

Nothing about load monitoring anywhere in BCM2 ?

Uwe · Jul 20, 2020

Not that I found.

-Uwe-

DV52 · Jul 20, 2020

^^^^ Uwe: hmm...... I think that I'm correct in recalling a recent discussion (with someone here?) about MLB platform vehicles having MQB type Leucte-sets. If so, a fix that I found useful on my test bench to stop these nag messages was to set the Fehlerort mittleres Byte DTC-DFCC and Lampendefektbitposition channels to zero on the appropriate Leuchte-sets. It worked on the early model BCM on my test-bench - but for some unknown reason, it no longer worked on the newer style BCMs that had a zero long-code string. I note that OP's BCM does indeed have a non-zero long-code string.

@nugentp: Hi. Pending the accuracy of my failing memory and just because it's an easy try - perhaps you could create and post-up an adaptation channel map of the hex09 module. I'm assuming that this is the module that has Leuchte-sets -rather than the hex46 module. I think the BCM does hold these channels because the SSP for the A6/C7 says that the hex09 module controls the headlight assemblies.

To aid me in making sense of the admap data - please configure the dialogue box for the file creation like this:

Don

nugentp · Jul 21, 2020

DV52 said:
^^^^ Uwe: hmm...... I think that I'm correct in recalling a recent discussion (with someone here?) about MLB platform vehicles having MQB type Leucte-sets. If so, a fix that I found useful on my test bench to stop these nag messages was to set the Fehlerort mittleres Byte DTC-DFCC and Lampendefektbitposition channels to zero on the appropriate Leuchte-sets. It worked on the early model BCM on my test-bench - but for some unknown reason, it no longer worked on the newer style BCMs that had a zero long-code string. I note that OP's BCM does indeed have a non-zero long-code string.

@nugentp: Hi. Pending the accuracy of my failing memory and just because it's an easy try - perhaps you could create and post-up an adaptation channel map of the hex09 module. I'm assuming that this is the module that has Leuchte-sets -rather than the hex46 module. I think the BCM does hold these channels because the SSP for the A6/C7 says that the hex09 module controls the headlight assemblies.

To aid me in making sense of the admap data - please configure the dialogue box for the file creation like this:

Don

I will actually do that for both BCMs - 09 and 46 - the nag alarms about the reverse lamps are definitely associated with 46. Happy for any other eyeballs to find where cold / load monitoring is defined for these on the C7 platform.

hadez16 · Jul 21, 2020

Open unit 46
Login with 16017

Then you have two options:

1) Report value of adaptation channel 191 and receive a new value just for deactivating reverse lamp error detection

2) Set channel 181 to 0 in order to deactivate all error detection for rear lighting

nugentp · Jul 21, 2020

hadez16 said:
Open unit 46
Login with 16017

Then you have two options:

1) Report value of adaptation channel 191 and receive a new value just for deactivating reverse lamp error detection

2) Set channel 181 to 0 in order to deactivate all error detection for rear lighting

Interesting you mention channel 181 as I saw that referenced in another Audi forum with a specific value that did NOT work for me - hoping that a value of 0 will disable all rear monitoring as you suggest - then maybe can reverse engineer which of those 16 bits relate to the reverse lamp monitoring.

Is the reference to 191 (one nine one) above a typo ?

nugentp · Jul 21, 2020

Happy to report that changing channel 181 from 65535 to 0 turned off the reverse lamp nags - I will try to find out which bit(s) are controlling that. Will take a bit of time with a kind of binary tree. Many thanks for the pointer here.

nugentp · Jul 21, 2020

Right - magic - it is sorted and I now know which bits are controlling it. The reverse light nag alarm is off at 0-1-3-7-15-63-127-255-511-1023 but at 2047 the LEFT nag alarm is triggered. At 4095, both nag alarms are triggered... so its bits twelve and eleven involved here.

So, 65535 - 2^11 - 2^10 = 62463

In binary that is 1111 0011 1111 1111 = no more reverse light nags - woop.

In time I might try to document the other bits, but this is a nice find.

hadez16 · Jul 22, 2020

Is the reference to 191 (one nine one) above a typo ?

I dount mak typongs.

AFAIK....! Channel 181 determines the load types, and Channel 191 and 192 really controls the error detection itself.

nugentp · Jul 22, 2020

Interesting...
Channel 191 is also set to 65535 - made no change
Channel 192 is set to 3 - no changes here either

The alarm masking bits in channel 181 worked well enough for my need - if the wife's wagon nags about faulty lamps, then I get nagged at as a direct result lol.

hadez16 · Jul 22, 2020

nugentp said:
Interesting...
Channel 191 is also set to 65535 - made no change
Channel 192 is set to 3 - no changes here either

The alarm masking bits in channel 181 worked well enough for my need - if the wife's wagon nags about faulty lamps, then I get nagged at as a direct result lol.

Just as a test. Reset 181 to original value and try changing channel 191 to 62463.....

nugentp · Jul 22, 2020

hadez16 said:
Just as a test. Reset 181 to original value and try changing channel 191 to 62463.....

Roger that - will post findings on that later today hopefully.

C7 A6 Allroad - LED Reverse Lamp retrofit - Coding problem

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