LED Bulb Coding - License Plate Light Without Pulse Width Modulation Option

   #41  

GaryM

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Gary: please excuse my ignorance where your car is concerned, but there is a PWM situation that does approximate to the DC trace that keeps showing-up on your scope: when the duty cycle of the waveform is 100%! It's probably a dumb question- but was there any form of dimming on the lamps that you used in your tests?
Yes, it's quite possible that the license plates on my car are set to 100% brightness meaning that PWM would be at full duty cycle, however there is no way to change brightness for the license plate bulbs in VCDS. It may be possible with the other tool I have by directly editing memory cell values, but I would first need to be reasonably confident that the memory cells I'm messing with are actually for the license plate bulb configuration because I don't really want to risk inadvertently damaging something just for the sake of trying to prove something :eek:
 
   #42  

PetrolDave

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After market HID are supposed to be failed on the MOT test as most them have no headlamp washers or any self levelling devices.
Sorry that is't true - please read the online MOT Test Guidelines. IF headlamp washers or self-levelling are fitted they MUST work to pass the MOT, but they are NOT required to be fitted to pass the MOT Test.

Having said that, a vehicle in the UK with HID headlamps that does not have headlamp washers & self-levelling is illegal as it does not comply with the relevant ECE Regulations.

The key thing to remember is that the MOT test is NOT a test of legality, it's merely a test of roadworthiness - but one that is full of anomalies that compromise real world safety (another one is that the SRS warning lamp does not have to work but the ABS warning lamp does have to work...).
 
   #43  

GaryM

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I've now had time to do some extensive testing of the two configuration settings in question (post #1) with no bulbs fitted, with incandescent bulbs fitted, and with LED (non CAN Bus version) bulbs fitted. For each of these 3 bulb type scenarios, I have tried every permutation of the license plate bulb configuration settings to find out whether the Bulb Check Warning Light illuminates or not.

What I believe I have concluded from this test is that the "License Plate Light w/o Pulse Width Modulation (PWM) [LED Light]" setting has nothing to do with a reduced PWM voltage to the bulbs to try and increase their life at all. I now believe that this "PWM" setting is actually to do with warm bulb diagnosis (sometimes also known as hot bulb dignosis) instead whereby a high frequency PWM signal is likely passed through the bulb while it is switched on to check that there is circuit continuity through it. The results in the tables below seem to back up this theory coupled with the fact that I wasn't seeing a ~12v PWM voltage on the bulb supply when PWM was activated on the license bulb plate supply (i.e. the "without PWM" setting was switched off). It's unfortunate that one setting is the reverse of the other (one of them ticked means "inactive" while the other ticked means "active") as it makes it harder to get your head around interpreting the results. I've therefore also included a second "translated" table which makes it easier for your brain to interpret the results from a visual perspective :D

  • Cold Bulb Diagnosis
    This is only performed when the ignition is first switched on. This checks each of the bulb circuits for continuity/resistance and will illuminate the Bulb Check Warning Lamp if there are found to be anomalies in any of the bulb circuits. Once the cold diagnosis test completes, it does not continue to check the bulbs so if something happens to a bulb in any of the circuits after the initial cold diagnosis checks were performed, the Bulb Check Warning Lamp will not illuminate. That will only happen if the lights on that particular circuit are switched on (which invokes the warm bulb diagnosis test), or if the ignition is cycled off and back on again.

  • Warm Bulb Diagnosis
    This is performed on a particular circuit whenever the light switch for that circuit is switched on. The diagnosis continues to operate for the duration that the lights remain switched on for on that circuit, so that if any bulbs blow while in use, the Bulb Check Warning Lamp will immediately illuminate as soon as that happens.

The tables below pretty much speak for themselves but this is a brief summary:-

  • With no bulbs fitted at all, you always get a "bulb out" warning whether under an "ignition on" or "light switch on" condition.

  • The settings and "bulb out" warnings for incandescent bulbs seem to be consistent with what you would expect.

  • The settings for LED bulbs seem to be mostly logical except for row 12 in the Table A (row 10 in Table B). With cold diagnosis switched on I would expect to see a "bulb out" warning appear but it is having the opposite effect. Not so with the warm diagnosis though which if switched on always flags up a "bulb out" warning for the LED bulbs (rows 9 & 10 in Table A, rows 11 & 12 in Table B). So, for LED bulbs you at least need to switch off the warm diagnosis (i.e. switch on the "Without PWM" setting).

Table A:




Table B:



This shows the same results as Table A but with the "Without PWM" column changed to "Lamp Monitoring (Warm)" and the values within that column inverted, plus the rows swapped around so they remain sequential from a logical bit value perspective. For both columns, a bit value of 0 means "switched off" and a bit value of 1 means "switched on". For each bulb type, you can see a much more obvious "pattern" emerging in Table B (green no's to the left, red yes's to the right).


@RT: Might be worth double-checking the source of the description for Byte 17, Bit 7 on the PQ35 BCMs. I don't know where the descriptions come from but maybe it's one that has just got "lost in translation" or one that just isn't worded particularly well in the document or system it came from :confused:
 
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   #44  

GaryM

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I realised I forgot to include an updated Auto-Scan of my car so below is a new one I did this morning. This is with non Can Bus LED license plate bulbs fitted, and with the following license plate bulb settings applied in the BCM which prevent the Bulb Check Warning Light illuminating for the license plate bulb circuit:-

  • Byte 17 Bit 7 -> License Plate Light w/o Pulse Width Modulation (PWM) [LED Light] -> Enabled (ticked/active)

  • Byte 23 Bit 6 -> Lamp Monitoring (Cold) License Plate Lamps active -> Disabled (unticked/inactive)

Code:
Saturday,20,May,2017,09:50:49:55895
VCDS -- Windows Based VAG/VAS Emulator Running on Windows 10 x64
VCDS Version: 17.1.3.0 (x64)
Data version: 20170320 DS267.7
www.Ross-Tech.com


VIN: VSSZZZ1PZCRXXXXXX   License Plate: 
Mileage: 39430km-24500mi   Repair Order: 



--------------------------------------------------------------------------------
--------------------------------------------------------------------------------


Chassis Type: 1P (7N0)
Scan: 01 02 03 08 09 10 15 16 17 19 25 2E 37 42 44 46 52 55 56 62
          72

VIN: VSSZZZ1PZCRXXXXXX   Mileage: 39430km-24500miles

01-Engine -- Status: OK 0000
02-Auto Trans -- Status: OK 0000
03-ABS Brakes -- Status: OK 0000
04-Steering Angle -- Status: OK 0000
08-Auto HVAC -- Status: OK 0000
09-Cent. Elect. -- Status: OK 0000
10-Park/Steer Assist -- Status: OK 0000
15-Airbags -- Status: OK 0000
16-Steering wheel -- Status: OK 0000
17-Instruments -- Status: OK 0000
19-CAN Gateway -- Status: OK 0000
25-Immobilizer -- Status: OK 0000
2E-Media Player 3 -- Status: OK 0000
37-Navigation -- Status: OK 0000
42-Door Elect, Driver -- Status: OK 0000
44-Steering Assist -- Status: OK 0000
46-Central Conv. -- Status: OK 0000
52-Door Elect, Pass. -- Status: OK 0000
55-Headlight Range -- Status: OK 0000
56-Radio -- Status: OK 0000
62-Door, Rear Left -- Status: OK 0000
72-Door, Rear Right -- Status: OK 0000
 
-------------------------------------------------------------------------------
Address 01: Engine (CEG)       Labels: 03L-906-022-CBA.clb
   Part No SW: 03L 906 022 TP    HW: 03L 906 022 GP
   Component: R4 2,0L EDC G000AG  5763  
   Revision: 13H14---    Serial number:               
   Coding: 0000078
   Shop #: WSC 06402 785 00200
   VCID: 0603B34371FD7A71D3-8052

No fault code found.
Readiness: 0 0 0 0 0 

-------------------------------------------------------------------------------
Address 02: Auto Trans        Labels: 02E-927-770.clb
   Part No SW: 02E 300 057 N    HW: 02E 927 770 AL
   Component: GSG DSG AG6     512 3101  
   Revision: 05551213    Serial number: 00001111122064
   Coding: 0000020
   Shop #: WSC 06402 785 00200
   VCID: 2447C9CBE701A861AD-8070

No fault code found.

-------------------------------------------------------------------------------
Address 03: ABS Brakes (J104)       Labels: 1K0-907-379-60EC1F.clb
   Part No SW: 1K0 907 379 BJ    HW: 1K0 907 379 BJ
   Component: ESP MK60EC1   H31 0121  
   Revision: 00H31001    
   Coding: 163B6012092600FD680C06E4901A0082350800
   Shop #: WSC 04941 000 00000
   VCID: 7BF5D2B7FA3F3799BC-802E

No fault code found.

-------------------------------------------------------------------------------
Address 08: Auto HVAC (J255)       Labels: 5K0-907-044.clb
   Part No SW: 5P0 907 044 S    HW: 5P0 907 044 S
   Component: Climatronic   H18 0804  
   Revision: 00001001    
   Coding: 0000000002
   Shop #: WSC 06402 785 00200
   ASAM Dataset: EV_Climatronic A01010
   ROD: EV_ClimaAutoBasis_SE35.rod
   VCID: 408F655BDB599441A9-8014

No fault code found.

-------------------------------------------------------------------------------
Address 09: Cent. Elect. (J519)       Labels: 1K0-937-08x-09.clb
   Part No SW: 5K0 937 087 R    HW: 5K0 937 087 R
   Component: BCM PQ35 H    021 0064  
   Revision: BE021001    
   Coding: 46180A3EE025B0C042080080950009C442D50008727D8520008040000040
   Shop #: WSC 54559 001 104857
   VCID: 4487694BC74188618D-8010

   Subsystem 1 - Part No: 1P0 955 119 D  Labels: 1KX-955-119.CLB
   Component: Wischer 24111  26  0611 
   Coding: 00DB90

   Subsystem 2 - Part No SW: 1P0 955 559 A    HW: 1P0 955 559 A  Labels: 1P0-955-559.CLB
   Component: REGENLICHTSEN  H04 0003 
   Coding: 02542E

   Subsystem 3 - Part No: 1P0 951 171 A
   Component: Innenraumuebe  010 4974 
   Coding: 000000

   Subsystem 4 - Part No: 1K0 951 605 C
   Component: LIN BACKUP HO  H05 1501 
   Coding: 000000

No fault code found.

-------------------------------------------------------------------------------
Address 10: Park/Steer Assist (J446)       Labels: 3C8-919-475.clb
   Part No SW: 5P0 919 475 C    HW: 8P0 919 475 N
   Component: PARKHILFE 8K  H08 0008  
   Revision: --------    Serial number: 12561133903563
   Coding: 100104
   Shop #: WSC 04941 000 00000
   VCID: 3B7512B7BABFF799FC-806E

No fault code found.

-------------------------------------------------------------------------------
Address 15: Airbags        Labels: 5N0-959-655.lbl
   Part No SW: 5N0 959 655 R    HW: 5N0 959 655 R
   Component: J234__A0E VW10 HI   1918  
   Revision: 23016000    Serial number: 003K0PPTCX2K  
   Coding: 0012357
   Shop #: WSC 06402 785 00200
   VCID: 4C97416B2F11402145-8018

   Subsystem 1 - Serial number: 6332MTS610773401 

   Subsystem 2 - Serial number: 6342MTS643573401 

   Subsystem 3 - Serial number: 6351HTS66QJC0AKR 

   Subsystem 4 - Serial number: 6361HTS6UVFA0AKJ 

   Subsystem 5 - Serial number: 00000000000000000

   Subsystem 6 - Serial number: 00000000000000000

No fault code found.

-------------------------------------------------------------------------------
Address 16: Steering wheel (J527)       Labels: 5K0-953-569.clb
   Part No SW: 5K0 953 521 AT    HW: 5K0 953 569 B
   Component: LENKS.MODUL   014 0140  
   Revision: FF010040    Serial number: 20111207200300
   Coding: 189A140002
   Shop #: WSC 06402 785 00200
   ASAM Dataset: EV_SMLSNGVOLWSXS A01004
   ROD: EV_SMLSNGVOLWSXS.rod
   VCID: 7EF3DBA3E12D22B19B-802A

   Multifunction steering wheel control module: 
   Subsystem 1 - Part No SW: 1P0 959 538 B    HW: 1P0 959 538 B  Labels: 3C8-959-537.CLB
   Component: E221__MFL-TAP  H02 0102 
   Coding: E30000

No fault code found.

-------------------------------------------------------------------------------
Address 17: Instruments (J285)       Labels: 5K0-920-xxx-17.clb
   Part No SW: 1P0 920 950 K    HW: 1P0 920 950 K
   Component: KOMBI         H05 0607  
   Serial number: 00000000000000
   Coding: 410F01
   Shop #: WSC 131071 1023 2097151
   ASAM Dataset: EV_Kombi_UDS_VDD_RM09 A04114
   ROD: EV_Kombi_UDS_VDD_RM09_SK46.rod
   VCID: 3561048F949B21E90A-8060

No fault code found.

-------------------------------------------------------------------------------
Address 19: CAN Gateway (J533)       Labels: 7N0-907-530-V2.clb
   Part No SW: 7N0 907 530 M    HW: 1K0 907 951 
   Component: J533  Gateway H42 1623  
   Revision:   H42       Serial number: 281111F1000312
   Coding: 350203
   Shop #: WSC 04941 000 00000
   VCID: 3A7B17B3B585CE91E7-806E

No fault code found.

-------------------------------------------------------------------------------
Address 25: Immobilizer (J334)       Labels: 5K0-920-xxx-25.clb
   Part No SW: 5K0 953 234     HW: 5K0 953 234 
   Component: IMMO          H05 0607  
   Serial number:               
   Coding: 000000
   Shop #: WSC 00000 000 00000
   ASAM Dataset: EV_Immo_UDS_VDD_RM09 A03009
   ROD: EV_Immo_UDS_VDD_RM09_VW21.rod
   VCID: 6ADBE7F38DA5BE1157-803E

No fault code found.

-------------------------------------------------------------------------------
Address 2E: Media Player 3 (J650)       Labels: 5N0-035-342.lbl
   Part No SW: 5N0 035 342 E    HW: 5N0 035 342 E
   Component: SG EXT.PLAYER H13 0240  
   Revision: A1001003    Serial number: 7661443894    
   Coding: 010000
   Shop #: WSC 04941 000 00000
   VCID: 2959D8FF402375099E-807C

No fault code found.

-------------------------------------------------------------------------------
Address 37: Navigation (J794)       Labels: 1K0-035-27x-37.clb
   Part No SW: 5P0 035 191 G    HW: 5P0 035 191 G
   Component: RNS315-EU   H35 0263  
   Serial number: SEZAZ2L9157843
   Coding: 040004010402000000000002
   Shop #: WSC 06402 785 00200
   ASAM Dataset: EV_RNS315EUV2UDS A01004
   ROD: EV_RNS315EUV2UDS.rod
   VCID: 2F6D36E776C71B3940-807A

   Data medium: 
   Subsystem 1 - Part No: 3AA 919 866 
   Component: EUR_W_V7  0066 

No fault code found.

-------------------------------------------------------------------------------
Address 42: Door Elect, Driver (J386)       Labels: 3C0-959-70X-GEN4.clb
   Part No SW: 3C8 959 701     HW: 3C0 959 793 C
   Component: TUER-SG FT    002 0508  
   Revision: 12110009    Serial number: 0003506013
   Coding: 0012B0
   Shop #: WSC 06402 785 00200
   ASAM Dataset: EV_TSGFPQ35BRFVW46X A04001
   ROD: EV_TSGFPQ35BRFVW46X.rod
   VCID: 6DD1ECEFBC4BA92932-8038

   Slave Driver: 
   Subsystem 1 - Part No SW: 3C0 959 704 E    HW: 3C0 959 794 E  Labels: 1K0-959-70X-GEN4.CLB
   Component: J389__TSG-HR  007 1501 
   Serial number: 00000006219061      
   Coding: 000290

No fault code found.

-------------------------------------------------------------------------------
Address 44: Steering Assist        Labels: 1K0-909-14x-GEN3.clb
   Part No: 1K0 909 144 N
   Component: EPS_ZFLS Kl. 142    3301  
   Revision: 00H22000    
   Shop #: WSC 06402 785 00200
   VCID: 3561048F5C9B21E90A-8060

No fault code found.

-------------------------------------------------------------------------------
Address 52: Door Elect, Pass. (J387)       Labels: 3C0-959-70X-GEN4.clb
   Part No SW: 3C8 959 702     HW: 3C0 959 792 C
   Component: TUER-SG BT    002 0508  
   Revision: 14110009    Serial number: 0003506882
   Coding: 0012B0
   Shop #: WSC 06402 785 00200
   ASAM Dataset: EV_TSGBPQ35BRFVW46X A04001
   ROD: EV_TSGBPQ35BRFVW46X.rod
   VCID: 6ED3EBE3B14D52310B-803A

   Slave Passenger: 
   Subsystem 1 - Part No SW: 3C0 959 703 E    HW: 3C0 959 795 E  Labels: 1K0-959-70X-GEN4.CLB
   Component: J388__TSG-HL  007 1501 
   Serial number: 00000006236000      
   Coding: 000290

No fault code found.

-------------------------------------------------------------------------------
Address 55: Headlight Range        Labels: 5M0-907-357-V2.lbl
   Part No SW: 5M0 907 357 C    HW: 5M0 907 357 C
   Component: AFS-Steuergeraet    0148  
   Revision: 00H04000    Serial number:               
   Coding: 2557189
   Shop #: WSC 06402 785 00200
   VCID: 3467398B57E138E13D-8060

   Subsystem 1 - Part No: 7L6 941 329 C  Labels: 3D0-941-329.CLB
   Component: AFS-Lst.-Modul l    0004  
   Coding: 00000039

   Subsystem 2 - Part No: 7L6 941 329 C  Labels: 3D0-941-329.CLB
   Component: AFS-Lst.-Modul r    0004  
   Coding: 00000039

No fault code found.

End-------------------------(Elapsed Time: 02:51)--------------------------
 
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   #45  

jasons6930

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Well, my celebrations were short lived with my LED stop/tail.



Interestingly i never had any bulb out warnings.

Not sure what the on on on off off means though.

I'll monitor this over the next week or so before i start tweaking dimming, although i'm wondering of it was a voltage spike that caused the fault?

Should i reduce the voltage via dimming?

14V seems a bit high, and the time suggests it was me starting the van to go to work when the auto lights came on.
 
   #46  

GaryM

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The fault is showing as "Intermittent" which is probably the reason why the Bulb Check Warning Lamp didn't illuminate. You can test this by completely removing the bulb and then switching on the ignition. The cold diagnosis check should then kick in and detect a problem with the bulb which should then trigger illumination of the Bulb Check Warning Lamp. You should also find that the DTC is then listed as a normal open or short circuit fault rather than an intermittent one. If you are getting intermittent DTCs now then it may only be a matter of time before a non-intermittent DTC appears during normal use of the lights and your Bulb Check Warning Lamp does then come on.

The 14.3v is just the voltage that the battery was outputting at the time of the fault. It is not necessarily the voltage that is reaching the bulb. Even if it was, LED bulbs have a voltage regulator built into them which brings down the voltage that reaches the actual on circuit diodes themselves. I have a couple of Osram 7556CW-02B P21W LED bulbs and testing these with a bench power supply shows that any voltage above 6v will turn the LEDs on but they remain the same constant brightness no matter what voltage above 6v is applied to them.

I'm pretty sure I've seen an explanation on the RT forums before as to what the "ON ON ON OFF OFF" freeze frame data actually means with regards to voltage data values but I can't find it now. Hopefully someone from RT will pipe up with a renewed explanation in this thread :)
 
   #47  

jasons6930

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The fault is showing as "Intermittent" which is probably the reason why the Bulb Check Warning Lamp didn't illuminate. You can test this by completely removing the bulb and then switching on the ignition. The cold diagnosis check should then kick in and detect a problem with the bulb which should then trigger illumination of the Bulb Check Warning Lamp. You should also find that the DTC is then listed as a normal open or short circuit fault rather than an intermittent one. If you are getting intermittent DTCs now then it may only be a matter of time before a non-intermittent DTC appears during normal use of the lights and your Bulb Check Warning Lamp does then come on.

The 14.3v is just the voltage that the battery was outputting at the time of the fault. It is not necessarily the voltage that is reaching the bulb. Even if it was, LED bulbs have a voltage regulator built into them which brings down the voltage that reaches the actual on circuit diodes themselves. I have a couple of Osram 7556CW-02B P21W LED bulbs and testing these with a bench power supply shows that any voltage above 6v will turn the LEDs on but they remain the same constant brightness no matter what voltage above 6v is applied to them.

I'm pretty sure I've seen an explanation on the RT forums before as to what the "ON ON ON OFF OFF" freeze frame data actually means with regards to voltage data values but I can't find it now. Hopefully someone from RT will pipe up with a renewed explanation in this thread :)
Thanks Gary.

Im also intrigued to know how the vehicle applies the tail light function of the lamp, considering it is only a single contact variety.
 
   #48  

GaryM

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Im also intrigued to know how the vehicle applies the tail light function of the lamp, considering it is only a single contact variety.
The two different brightness levels of tail lights for position lamps and braking lamps on a single contact / single filament bulb will be achieved either by using PWM or by controlling the current to the bulb. Either one of these will be controlled by the BCM. PWM has already been discussed, but if current control is the mechanism being employed, then below is an explanation as to how that would be working...

Think of a traditional dual filament bulb on older cars with old school wiring (just analogue relays and switches with no electronic control modules) which have a 5w output on one filament and a 21w output on the other filament. Each of the two filaments in the bulb is just switched on or off separately by two different voltage supply wires. Newer cars with a BCM have the ability to achieve the same 5w / 21w outputs but by using only a single filament bulb and a single voltage supply wire by controlling the current supplied to the bulb on that single wire. 5w being the "normal" brightness for position lamps on the tail lights, and 21w being the full lamp brightness for braking on the tail lights.

We need to apply Ohm's law to find out the current required for each brightness where I = P / V. We know that the voltage supply is 12 volts, so:-

  • To get the 5 watt output on a single filament bulb (the lower brightness)

    5 / 12 = 0.41​

    This means that when tail light position lamps are on, the BCM would be supplying the bulb with 0.41 amps of current to provide a 5 watt power output.

  • To get the 21 watt output on a single filament bulb (the higher brightness)

    21 / 12 = 1.75​

    This means that when the tail light brake lamps are activated, the BCM would increase the bulb supply current to 1.75 amps to provide a 21 watt power output.

Simples :D


Of course, it may actually be PWM that is being used to control the brightness and not current. I will test this for a definitive answer when I next get the opportunity. Either way, you now know how a bulb with only a single pair of contacts can have two different brightness levels :)
 
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   #49  

jasons6930

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Ok, as an update.

Got in to go to work and all ok, but then an hour later got in to go to job and actually had a bulb warning light on the dash with 'check rear stop light' on the display this time.

Seems like these are going to cause issues so looks like I'm beaten.

I'll do a scan and see what's it's recorded.
 
   #50  

GaryM

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Got in to go to work and all ok, but then an hour later got in to go to job and actually had a bulb warning light on the dash with 'check rear stop light' on the display this time.

Seems like these are going to cause issues so looks like I'm beaten.
It's unfortunate that the PQ35 BCMs in the later PQ35 platform cars are so sensitive to the resistive load of bulbs. The earlier 2005-2009 PQ35 platform cars that used an earlier type of BCM don't seem to be nearly as fussy with the type of LED bulbs used.

It goes to prove that expensive LED bulbs appear to be no better than the cheap ones at suppressing any fault codes.

If you can't live with the Bulb Check Warning Lamp staring you in the face and you don't want to go down the route of either memory cell editing or putting the incandescent bulbs back in, you do still have the option of wiring in some heavy duty resistors in parallel with the LED bulb (something like these ones). If you do this, be aware that some of these resistors can get quite hot so just make sure you try and mount them to something metal that will sink away any excess heat, and definitely keep them away from anything plastic that could risk being melted.
 
   #51  

jasons6930

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Thanks Gary,

I think for now i'll change them back to the normal ones.

I must admit, i wasn't really expecting a miracle, but it would have been nice for a change!
 
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