# F15 X5 towbar error, AHM module



## code505 (Nov 18, 2014)

Hello,

I have retrofitted Westfalia towbar with dedicated elctronic with the same kit:
BMW X5 - 303368900113_200 - Westfalia-Automotive

the module is doing it job disabling parking sensor and all lights in the trailer and bike carrier,
I thougt that I can code the car so is trailer is connected some changes to suspension or stability would be activated

I added 3AC and VO code, but now I got tow hitch error in my dash and centre console:

















I removed 3AC and VO code all modules except DME again but the error didn't clear.
ISTA+ is showing AHM unit in red, and several fault in other units indicate inability to connect to AHM (not SMFA, SMBF):










even after I disconnect the control module from the car it's still showing in ISTA.
what could be wrong and how to remove the module


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## jjan (Oct 21, 2015)

You should ad 235 not 3AC. Last one is the electrical hitch not the detachable. 


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## jjan (Oct 21, 2015)

So start over, add 235 to VO and Code everything. 


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## code505 (Nov 18, 2014)

I discovered that I added K235 to HO-Wort, after I deleted it and VO coded every thing is OK now.


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## agent_orange (Apr 21, 2019)

Interested to know a bit more about this, as I'm having minor issues with a Westfalia tow wiring module in a F25.

So are you saying that AHM now appears in the control unit tree as green after VO coding with 235 but without K235 HO-Wort?


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## BimmerSLO (Nov 19, 2017)

I believe Westfalia manuals clearly says there is no need to code the vehicle, becuse their module is doing communication with the vehicle. 

I found this thread as I am preparing to do a Westfalia tow bar retrofit.


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## agent_orange (Apr 21, 2019)

Yes that is correct, the Westfalia module works without coding required.

However I got a permanent CF2501 error against the EGS for 'no message' from 'transmitter AHM', and this even persisted and still couldn't be cleared after I had removed the Westfalia module and wiring to swap to another F25, which then also promptly got the CF2501 error.
Was hoping to solve the EGS error with some coding as I hate having permanent errors when there is nothing wrong with the car, but was not able to.
It may be possible that a CAN network re-sync or whatever it's called in ISTA could fix it, but I haven't found out more about that or tried it.


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## BimmerSLO (Nov 19, 2017)

I see.. that is a bummer...


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## BimmerSLO (Nov 19, 2017)

Well, as I installed Westfalia retorfit tow bar I encouter the same issue, same error. Did you manage to solve an issue with VO coding 235 option??

I also hate having erros, when nothing is wrong with the car. 

It seems that the car recognizes the tow bar over CAN, but does not know how to read from Westfalia module...


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## agent_orange (Apr 21, 2019)

I never ended up trying the 235 VO code or HO-Wort option after the adventures that the OP had with it on his F15, so still have the permanent CF2501 error on EGS.
Have been meaning to try a CAN network re-sync via ISTA but haven't had the time to research that.
The Westfalia install manual does make vague references to 'coding may be required' but no further details.


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## BimmerSLO (Nov 19, 2017)

Thank you for your reply. As explained in ISTA for CF2501 error document, this kind of comunication errors can be ignored if not multiplied:

"
Note:
These faults usually appear in large numbers. If only a single fault related to a missing message has been entered and no problems related to the function of the control unit are present, then the fault can be ignored.
"

However I am still looking in EGS to find if there is a code to tell EGS not to look for AHM module....


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## BimmerSLO (Nov 19, 2017)

Soooo, I decided to dig a bit more and wanted to add K235 to HO-Wort as retrofit option. The same as code505 did.

After I added K235 to HO-Wort, wrote FA to car, there still was not sign of AHM or AAG module in the car. Like it is not connected to CAN bus.

I guess car can not read Westfalia non OEM module. I don't know how code505 did it, but it does not activate module in my case. (That is if you install as Westfalia manuals and their module. OEM module is completly different story).

Only option left is to VO code affected modules or just FDL code options that needs to be changed as per manual. But I believe nothing would change or even make a mess, because module is not recognized.

CF2501 is still present and I kind of give up.

Cheers,
BimmerSLO


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## MaWe (Oct 29, 2021)

Hello,


I have the same problem on F31 from 2013.

I installed the tow bar from westfalia.

Light's in trailer works good, but PDC still working when i have trailer.

I'll try to code FA 3AC - nothing has changed, additionally I have on dash error of elektric trailer wiring ( In ista errors from comunication withAHM module in ICM, REM, EGS, DSC)
I'll try to code K235 - nothing has changed, additionally I have on dash error of elektric trailer wiring

I'll delete 3AC, K235 and only code using Bimmercode - pdc deactivation then trailer operation - PDC deactivates when trailer attached

Since the installation this tow bar I have problem with my automatic transmision.

When I stop on, after about 15 secondsI I feel a tug. When I disconnect the westfalia module everything is ok.




I'll try to code FA 3AC - nothing has changed, additionally I have on dash error of elektric trailer wiring
I'll try to code K235 - nothing has changed, additionally I have on dash error of elektric trailer wiring

Can anybody help ?


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## mrashton (Apr 30, 2012)

MaWe said:


> Hello,
> 
> 
> I have the same problem on F31 from 2013.
> ...


There is no need to add the VO codes you mention. Rather leave the VO as it was intended.

On my G32, the Parking assist module is "USS" and it will possibly be a different module on your car so you'll need to check but to disable the rear PDC when something is attached to the towbar I just changed this:


DescriptionModuleSectionItemNew valueDefault valueDisable rear PDC for 3rd Party Towbar electricsUSS300B PDC_VEHICLEis_trailer_act_binitwertinactive
 
Sorry, can't help with the transmission issue.


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## MaWe (Oct 29, 2021)

When I tried code VO 3AC and K235

I also have such an error as "BimmerSLO " and "agent_orange"



agent_orange said:


> I got a permanent CF2501 error against the EGS for 'no message' from 'transmitter AHM', and this even persisted and still couldn't be cleared after I had removed the Westfalia module and wiring


I think the error is caused by our coding K235 and 3AC 
After installation tow bar and wiring from westfalia but before I tired code the tow bar I don't have CF2501 error on ESG module.


Did You successfully removed this error or have It ??


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## agent_orange (Apr 21, 2019)

I never tried VO coding 3AC or HO-Wort K235 as others had tried it and it only led to problems, so that isn't the cause.
Westfalia module worked great with no coding, including the trailer graphics when reversing, lamp warnings from the trailer etc., it was just the annoying CF2501 EGS error that made it not perfect.
As mentioned before, after I had removed the Westfalia module from my first F25 before selling it, the CF2502 error still could not be cleared!
Which makes it possible that the CAN network gets upset somehow by the addition of the Wesfalia module, and there is a CAN re-sync option in ISTA and maybe a routine in Tool32 as well which could help but try at your own risk.


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## BimmerSLO (Nov 19, 2017)

I 100% agree with agent_orange. No coding required. I tried coding just to remove CF2501 error. Otherwise everything is working. As agent_orange said, it could we resync issue or as BMW rep said, that the car shoud have SW upgrade. However, I decided not to get bothered with error no more...


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## MaWe (Oct 29, 2021)

As for a error, I don't care too much .

But I have problem with automatic transmission.

When I stop on lights. I feel thug 

When westfalia module is disconnected , everting is fine

worse, there is a problem with the gearbox .


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## BimmerSLO (Nov 19, 2017)

Did you try to VO code to factory setting (removing K235 etc...)?


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## MaWe (Oct 29, 2021)

Yes, the problem was after mounting the hook , but before trying to code anything


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