Ford Mondeo Mk5 2017 – DRL “tear” stopped working after FORScan coding, HCM B1087:00-C8

Post #1

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Hi everyone,
I’m looking for some help with a FORScan issue on my 2017 Ford Mondeo Mk5 2.0 TDCi 180 HP.
VIN: WF0FXXWPCFGK54259
Before I started coding the car with FORScan, both front DRL “tear”/LED strips were working normally.
I was making several changes in FORScan, including:
cornering light activation,
disabling Auto Start-Stop,
TPMS-related changes,
and a few other coding changes.
During/after the coding I disabled the front DRL “tear” function. Since then, one of the DRL/LED strips no longer works when the ignition is on or the engine is running.
However, when I unlock the car with the key fob, both sides still illuminate slightly, so the LED itself does not appear to be completely dead.
FORScan now shows this fault in the HCM (Headlamp Control Module):
B1087:00-C8 – LIN Bus A
Status: DTC Present at Time of Request
I also have:
DDM – B1165:15-0A
I have cleared the DTCs several times, but B1087 immediately comes back.
I unfortunately did not save a backup of the original configuration before making the changes.
I have checked the BdyCM As-Built (726) configuration and currently have, among others:
<span>726-26-02 0000 0103 015A<br>726-27-01 0001 0100 0057<br>726-45-01 0A00 1F00 019D<br>726-46-01 0001 0101 0077<br>726-46-02 0100 0101 0078<br>726-50-01 108E</span>
I also have the complete BdyCM 726 As-Built and HCM 734 As-Built data available if needed.
I tried using FORScan's “Load factory AB”, but it fails with:
<span>Downloading WF0FXXWPCFGK54259.ab ERR</span>
I also tried accessing the Motorcraft As-Built service, but I am currently redirected to the Ford business account/login page and cannot obtain the factory <span>.ab</span> file.

My main question is:

Could I have changed an HCM/BdyCM configuration parameter that caused the HCM to lose communication with the DRL/LED module on LIN Bus A?
What would be the correct HCM/BdyCM As-Built values for this specific Mondeo with factory LED/FDL headlights?
Is there a way to restore the original factory configuration for my VIN without replacing/programming the HCM?
Any help identifying the exact As-Built parameter responsible for the DRL/“tear” function or B1087:00-C8 would be greatly appreciated.
I can provide screenshots of the HCM DTCs, HCM 734 As-Built and the complete BdyCM 726 As-Built if required.

Thanks in advance!
 
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Post #2

Right, let's separate the two problems, because the DRL "tear" and the B1087 are actually the same root cause.

B1087:00-C8 "LIN Bus A" in the HCM is a loss-of-communication with a LIN slave node — on Mk5 the front LED tear/DRL strips are driven by LED driver modules that hang off the HCM's LIN bus. The fact that the strip still glows faintly on unlock (welcome/approach lighting) tells us the LED and its power feed are alive, so this is almost certainly not a dead module or broken wire. When you disabled the DRL tear function in coding you very likely changed an HCM config byte that also tells the HCM whether to poll that LIN node. Now the module presence/config no longer matches, so the HCM logs a LIN fault and won't drive that side in ignition/run.

So the fix is in the HCM 734 As-Built, not the BdyCM 726 you pasted. The 726 lines matter for some lighting enables, but the tear-strip behaviour and this LIN fault live in 734.

Practical path:
  • Post your full HCM 734 As-Built current values — that's what we need to spot the byte you flipped.
  • If you remember which 734 lines you touched when you "disabled the front DRL tear," list them.
  • Tell me your exact FORScan version and license type (extended vs trial).

On the factory AB download "ERR": that's FORScan trying to pull the original As-Built from Ford's server, and it's a separate issue — usually the VIN isn't returned by the server, a network/server hiccup, or the extended-license lookup failing. It does not mean your module is bricked. Don't rely on it for recovery; we can rebuild the correct 734 config from a known-good reference instead.

If you want to work offline, the (Resource #645) Ford As-Built Compare Tool lets you load your current 734 next to a reference .ab/.abt and see exactly which address/value differs — that's the cleanest way to catch the changed byte once we have a good reference to compare against.

B1165:15-0A in the DDM (door module) is a different circuit (short to ground type) and probably unrelated to the tear strip — deal with the HCM first, then re-check if that one persists.

Post the 734 dump and we'll narrow it down.
 
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Post #3

Module=734 ()

01-01 4B8E 4B50 9647
01-02 1C9F 191E 6494
01-03 8C46 0300 0014
01-04 32CE 0000 1959
01-05 E700 0032 CE28
01-06 1919 0000 0074
01-07 0000 007C 11D0
01-08 0AFA A53C 436C
01-09 B780 8014 2333
01-10 422D 056A 648E
02-01 6E00 0700 B3
 
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Post #4

Thanks, that's exactly the block I needed to see.

Honest caveat first: I can read the 734 values you posted, but I don't have a verified, spec-matched factory reference for your exact car (LED headlamps with tear DRL) in front of me, so I'm not going to point at one nibble and claim "flip this bit" — on the HCM the tear/LIN-enable and the headlamp-type config sit close together, and guessing a byte on a lighting module that's already throwing a LIN fault is how people turn one dead strip into two.

What we can say from the evidence:
  • B1087:00-C8 (LIN Bus A) correlating exactly with you disabling the tear function strongly supports a config mismatch, not hardware — consistent with the faint welcome-light glow you still get.
  • The fix is to restore the original 734 value(s) you changed, so the HCM goes back to expecting/polling that LIN node.

So two practical questions before we touch anything:
  • Do you have any recollection of which 734 line(s) you edited when you turned off the tear DRL? Even "it was in the 01-0x range" narrows it hugely. FORScan's own change log / the config screen you used often labels it.
  • Do you have access to a known-good 734 As-Built from an identical-spec Mk5 (same 2017 facelift, LED headlamps with tear DRL)? That's the safest reference to diff against yours, especially since your "Load factory AB" is failing.

On the factory AB "ERR": that's the Ford server not returning the .ab for the VIN, separate from your local coding. Try it again on a different network/later, and confirm your extended-license expiry is current — but don't rely on it as your recovery path.

Also confirm your exact FORScan version and whether you're on extended license, since older builds handle 734 writes differently.
 
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