H7 Dipped/main Coding Question

[t0mb0]

Hi,

I have installed H7 headlights so now I want to make my dips come on when the mains are on. According to the information on the forum, this involves:

Module: 9
Byte: 22
Bit 1: Turned off

However, my Bit 1 is already off (and the dips definitely aren't coming on with the mains). My configuration for byte 22 is

Bit 0: 1
Bit 1: 0
Bit 2: 1
Bit 3: 1
Hex: 6D

Now, if I set Bit 2 to 0, then it has the desired effect of turning the dips on with the mains. Flicking the state of Bit 1 has no discernible effect. However, this appears inconsistent with all the information I can find online. Should I just do this and forget about it? I assume that each bit must map one to one with each function change or could it have unintended consequences?

My base vehicle is a Window Van (as it came straight from a camper converter) rather than a panel van - maybe that accounts for the difference?

Thanks for any help!

Tom

 

[Ed Webb]

Bits count right to left and the far left bit is bit 0.
Despite there being 8 bits by traditional counting the bits count 7 6 5 4 3 2 1 0

With that in mind are you changing the right bit?

Sorry if it sounds like I'm talking down to you. Not intended.

 

[Pauly]

MY18 vans have a new revision of BCM so could account for the differences ? Older vans have BCM ending 090B but I notice newer ones are now 090C
Generally you just need to reduce the hex value by 2 but if you have it working I wouldnt worry about it too much

 

[t0mb0]

Bits count left to right and the far left bit is bit 0.
Despite there being 8 bits by traditional counting the bits count 7 6 5 4 3 2 1 0

With that in mind are you changing the right bit?

Sorry if it sounds like I'm talking down to you. Not intended.

Surely bit 0 is the least significant bit (as shown in your 7 6 5 4 3 2 1 0) and therefore the far right bit is bit 0?

 

[Ed Webb]

Surely bit 0 is the least significant bit (as shown in your 7 6 5 4 3 2 1 0) and therefore the far right bit is bit 0?

Yep my error, I've edited my post.

 

[t0mb0]

MY18 vans have a new revision of BCM so could account for the differences ? Older vans have BCM ending 090B but I notice newer ones are now 090C
Generally you just need to reduce the hex value by 2 but if you have it working I wouldnt worry about it too much

My van was purchased in Summer 2016 so I don't think it's that it's newer.

The working bit change (Bit 2 from 1 to 0), actually decreases the Hex by 4 - as you'd expect. But the hex is just a compact encoding of the binary number - surely the underlying logic is just assessing the state of each bit to decide what logic to apply when the mains are turned on?

 

[t0mb0]

Yep my error, I've edited my post.

Phew, I was about to get really confused!

 

[t0mb0]

MY18 vans have a new revision of BCM so could account for the differences ? Older vans have BCM ending 090B but I notice newer ones are now 090C
Generally you just need to reduce the hex value by 2 but if you have it working I wouldnt worry about it too much

My BCM does end 090B. My best guess is that it’s different because it’s a window van rather than a panel van, but who knows....

I assume that flipping the bit that has the right effect shouldn’t have any unintended consequences so I’ll flip it and see.

 

[Loz]

Change to 6B

 

[zebra]

I’ve a T6 Beach and did the H4>H7 mod. BCM is 90B and byte 22 was 6D just like yours. I changed to 6B based on what I’ve read. However I just checked and you’re right changing to 69 has the same effect.
Looking back through other coding threads @Robert said he originally had H7 lights and had bit 1-0, bit 2-0.
Ultimately both values seem to work, not noticed any negative effect from 6B for last few weeks.

 

[t0mb0]

I’ve a T6 Beach and did the H4>H7 mod. BCM is 90B and byte 22 was 6D just like yours. I changed to 6B based on what I’ve read. However I just checked and you’re right changing to 69 has the same effect.
Looking back through other coding threads @Robert said he originally had H7 lights and had bit 1-0, bit 2-0.
Ultimately both values seem to work, not noticed any negative effect from 6B for last few weeks.

Yep, that is consistent with mine. Changing the Hex to 6B does still work but I'm sticking with 69 given that it flips a single bit only to have the desired effect - I don't know what the effect flipping bit 1 to get to 6B actually is. Presumably it's nothing too serious, or you would have noticed.

 

[t0mb0]

Actually, turning bit 2 to 0 is completely consistent with this information:

VCDS codes list

I guess there are just two different variations out there for different vans.

 

[zebra]

Yeah that’s right, just leaves the function of bit 1 as an unknown for now.

 

[Pauly]

Just updated my VCDS and the bit has now keen added to the label file so this process is now a tick box exercise if you are running the latest software

 

[t0mb0]

Just updated my VCDS and the bit has now keen added to the label file so this process is now a tick box exercise if you are running the latest software

Which bit is it that’s been added? Is it turning bit 2 off?

 

[Pauly]

Yes there’s a tick box for bit 2

 

[t0mb0]

Yes there’s a tick box for bit 2

View attachment 22651

Ah, excellent. That’s definitely consistent with my experience. I guess some of the early results which reduced the hex by 2 also switched bit 1 to on at the same time. We still don’t know what this does, but no one has reported any strange behaviour so it can’t be anything too bad.

 

[Ed Webb]

Just updated my VCDS and the bit has now keen added to the label file so this process is now a tick box exercise if you are running the latest software

I like to think the forum discovered that one! Good work all.

 

[Loz]

DRL off with handbrake on should also be there..

 

[Pauly]

Yes it is think they refer to it as parking brake
You been talking to Ross tech again