Trailer module related fault codes

drsmithy : Hi.

Hmm......... the date stamp on the 136203 error is 2024.09.06 (remember, the date-format is American). This is the date when the error was first recorded in the module's fault memory. Does this date align with the installation of the trailer module?

I've included below a copy of the VCDS Freeze Frame data for same error from another VAG vehicle - which I thieved from the electric internet:

Code:

 136203 - Supply Voltage
P1757 00 [047] - Open Circuit
Confirmed - Tested Since Memory Clear
Freeze Frame:
Fault Status: 00000001
Fault Priority: 3
Fault Frequency: 1
Reset counter: 40
Mileage: 1578 km
Date: 2023.05.13
Time: 13:37:31

Notice that the Freeze-Frame entry Fault Frequency is missing from your extract of the part-SCAN. This is unfortunate because Fault Frequency indicates how many times the same fault has reappeared since first registration. I suggest that you remove the tick from UDS aggressive mode on the VCDS Auto-Scan screen (see below) and make another SCAN report. If the same fault remains, the Fault Frequency entry should add value to your hypothesis - maybe?

Finally, I'm not sure if you are aware of the impact of the trailer module on the VW Tiguan Dynamic Road Sign Display function - read below (thieved from HERE)

Trailer mode
On vehicles with a trailer hitch installed at the factory and a trailer that is connected to the vehicle electrical system, the display of road signs relevant to a trailer, such as the valid speed limit and passing restrictions for vehicles with a trailer, can be activated and deactivated in the vehicle settings in the Infotainment system ⇒ Vehicle settings menu.

For trailer mode, the display of valid speed limits can be adjusted to the model of the trailer and to the legal regulations. The setting can be set in increments of m10 km/h (5 mph) within a range of approx. 60 km/h (35 mph) and approx. 130 km/h (80 mph). If a speed is set that is higher than the permitted speed for driving wit a trailer in the country or state where the vehicle is being operated, the Dynamic Road Sign Display function will automatically display the legal speed limit, for example approx. 80 km/h (50 mph) in California.

Maybe deactivate Trailer mode - does the error message still appear?

Don

Since I'm probably going to get into an argument about this with a VW dealer later today, interested in people's thoughts.

Car is an MY20 Tiguan Allspace.

Not long after getting the car I used an OBD11 to make a number of small coding changes (dash graphics, disable seatbelt warning, etc). One of these was enabling the speed limit recognition, which is officially not a feature of AU cars but worked fine (or as well as it does, at least).

About 18 months ago I had a "genuine VW towbar" (yes, I know) installed by $DEALER. This started producing an error on the dash when starting the car "Error: Dynamic Road Sign Display" and the speed sign recognition stopped working. Since it wasn't a major problem, we were leaving on a trip shortly after and $DEALER was a fair distance away I left it to get fixed at some point in the future.

The next service - still not fixed - I asked my regular mechanic to have a quick look and see if he could fix it. He said no, but also highlighted the following fault from a VCDS scan and said it was probably related:

Code:

Address 69: Trailer (J345) Labels:I 5O0-907-383.clb
  Part No SW: 5O0 907 383 N HW: 5O0 907 383 N
  Component: Anhaenger H27 0264
  Revision: 8A001003 Serial number: 0537602958
  Coding: 0300000202000000
  Shop #: WSC 12345 123 61029
  ASAM Dataset: EV_TrailFunctGener2Hella 001008
  ROD: EV_TrailFunctGener2Hella_VW37.rod
  VCID: 42C8B2E9D518108B9F-8016

1 Fault Found:
136203 - Supply Voltage
    P1757 00 [00001001] - Open Circuit
    Confirmed - Tested Since Memory Clear
   Freeze Frame:
        Fault Priority: 3
       Reset counter: 195
       Mileage: 58090 km
       Date: 2024.09.06
       Time: 10:58:49

No worries, I thought, I was about to go and get a couple of things fixed under warranty before that expired, I'll get $OTHERDEALER (which is much closer) to look at this and fix it at the same time (because it's a "genuine VW towbar", right

).

Sadly no joy, they said even though it was a "genuine VW" towbar, they didn't do the install so I'd have to take it back to $DEALER for them to do it.

Now $DEALER is saying they can't/won't do anything because of the coding I've done (specifically the speed recognition, because that's what's appearing on the dash and they have erroneously spent time trying to fix because they didn't actually read the problem I wanted fixed - the fault in the trailer module).

I am reasonably sure the speed recognition error coming up on the dash is directly related to whatever the underlying fault being registered with the trailer module is, because it had been working fine before the towbar install and happened straight after.
I also feel pretty sure the converse is not true, and that the trailer fault identified above is not the product of enabling the speed sign recognition. That said I am basing it on the assumption that "open circuit" is a usefully descriptive error and there is actually an open circuit somewhere that's causing it.

Appreciate this is a bit of a niche question, but has anyone done both of these and can confirm they work together ? Or at least give me some confidence that they're not related in the sense that the speed sign recognition coding is causing the fault in the trailer module.

I have told the dealer all I want them to fix is the fault in the trailer module, but from a somewhat tense conversation late yesterday afternoon, I think they're going to use the speed sign recognition coding as an excuse to either not fix it, or charge $$$$$ (and possibly still not fix it).

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