GRA retrofit in Lupo 1.8t // CAN-Bus issue // Experts only!

My constellation of problems is quite complex, so please read carefully - professionals are welcome!

Starting situation:
My Lupo has been converted to a 1.8T engine with the engine code BJX (year of manufacture: 2006). The donor vehicle was a so-called "VW test platform" based on a Polo 9N GTI. However, the engine control unit (ECU) externally bears the serial number of a 2002 Sharan 1.8t 150 hp. When connected to a diagnostic tool, the ECU reports the data version of the Polo BJX. I suspect that VW, when building the test platform, simply took an ECU from stock, grabbed a Sharan ECU, and then reprogrammed it with the Polo software. As I said, this is just a guess... The renovation has been completed for a few months now, and everything is going great!

Objective:
I now want to retrofit my vehicle with a speed limiter (cruise control), as both the Sharan 1.8T and the Polo GTI are fundamentally capable of having it installed.

Problem:
The wiring (connecting the steering column switches directly to the MSG) and activation of the GRA (automatic headlight range adjustment) have been correctly completed, but unfortunately, it still doesn't work because I haven't installed the Polo-specific body control module (= CAN bus) since I have a Lupo, which doesn't require a central control unit for the electrical system (everything is controlled by individual modules).
My technician was able to use his diagnostic device (I believe it was measurement block 62, sub-item 8, or the reverse) to observe a change in all the "bits" when the controls of the GRA steering wheel switch and the brake, etc., were activated. Only the set switch does not lead to a change in the associated measured value!
The assumption is that MSG is expecting a CAN bus signal here. However, this pin definitely only receives an analog signal from the steering column switch.

Questions:
"I was told that I probably wouldn't have any problems if the MSG had the same data as the Sharan, since the Sharan (like my Lupo) doesn't have a body control module at all, and therefore, on that pin, it's not expecting a CAN bus signal, but rather an analog signal. It seems that the MSGs are physically identical. This leads me to wonder if it's possible to reprogram a pin on the MSG to expect an analog signal instead." It's actually a PIN, which wasn't previously registered.

2. Alternative: Could a CAN bus adapter be integrated into the analog line from the SET switch on the steering column to the MSG, converting the analog signal into a digital signal? Who could one contact regarding something like this?

"If none of the above options work, I'm considering buying a Polo body control module (BCM) on eBay and connecting the GRA (Gearbox Control Unit) to the MSG (Main System Module) through it. However, I'm very concerned that my MSG might then receive more errors from the BCM, since no windshield wipers, interior lighting, etc., would be connected to it. I fear that this could ultimately cause my MSG to go into a limp mode." Is there a way to avoid this?

4. More recommendations for a solution?

Background:
- I don't want to install a "universal" graphics card; I want to use the original feature.

Thank you for your help - sorry for the long text!
Best regards from Berlin, LowBlubbi.

Hello,

To be honest upfront: I don't know the solution, but I'm just offering guesses.

If the diagnostic system correctly identifies all positions of the GRA switch except for the "Set" button, then I suspect that the issue is not related to the CAN bus. In my opinion, it's likely that either the entire GRA (Gear Range Algorithm) switch will operate via CAN (Controller Area Network), or not a single bit will.

Therefore, my question is: Have you ever measured the voltage levels at the MSG pin to see how the voltage changes from one level to another when the set switch is activated? Which MSG pin did you connect the set switch to?

It would be easier for some MSG specialists if you could provide the part numbers of the MSGs (both the printed number and the diagnostic feedback).

Regards,
Guste.

Hi,

It wouldn't be the first time that a control knob like this has malfunctioned... so, use a multimeter to check if anything actually happens when you press the 'Set' button.

Best regards, Rainer.

Thank you very much for your excellent answers; I will try to get to the bottom of everything. Here are some answers to the questions that have been raised in the meantime:

I haven't been able to test the wiring of the steering column switch yet, but I will do so shortly. I also don't have the data (part numbers, etc.) for the control unit yet. I'm still waiting for my own diagnostic tool to be delivered. Regarding the wiring connections: The GRA wiring harness is connected to pin 38 (black), pin 57 (red), pin 75 (blue), and pin 76 (black) of the MSG (Main System Module). This is analogous to the GRA wiring configuration for a 1.8T Sharan.

The assumption that either all contacts of the steering wheel switch can be evaluated either analog or digitally (=CAN) is something I cannot either deny or confirm. However (!): The wiring harness for the steering wheel switch (what a word!) consists of four wires. Three of them are directly connected to the MSG (Modular Service Unit), as is done in both the Sharan and the Polo. However, the fourth wire (the SET signal) would need to be connected to the body control module in the Polo, whose data is stored in my MSG. This body control module is then connected to the MSG via the CAN bus. Therefore, my assumption is that the body control module does something (but what?) with the analog SET signal it receives from the steering wheel switch. Since it's exclusively connected to the MSG via the CAN bus, I suspect that the set signal is being converted from an analog to a digital format.

Therefore, I would be very happy if someone could answer my questions 1 and 2, if there is anyone here who has the knowledge to do so.

@Jochen_145, You say:

Quote:

Since the MSG on the CAN indicates whether GRA is active or not, the MSG is also the source that receives the analog signals from the GRA.

Here's the problem: The MSG only indicates that the GRA is active when it receives a corresponding signal that it can understand! And, of course, the MSG is the source that receives the analog signals; I described that in detail. What are you trying to tell me with that (and I don't mean it in a bad way!)?

Only the fourth cable (SET signal) needs to be connected to the vehicle's onboard network control unit, which, in the case of the Polo, has its data stored in my MSG (Main System Gateway), and which is connected to the MSG via the CAN bus. Therefore, my assumption is that the onboard network control unit is doing something (but what?) with the analog SET signal that it receives from the steering column switch. Since it's exclusively connected to the MSG via the CAN bus, I suspect that the set signal is being converted from an analog to a digital format.


Hello,
If my memory serves me correctly, you don't have a body control module installed.
However, if your MSG is expecting a message from this SG because the GRA is encoded, there should be an error message indicating a problem with the CAN bus or something similar.

I'm not familiar with the term 'Mischbeschaltung,' but I wouldn't necessarily consider that a reliable reference.
It's simply poorly executed, which I can't imagine happening right now.

What are you trying to tell me with that (and I don't mean it in a bad way!)?
The MSG (presumably a specific system or component) alone determines whether GRA (another system or component) is active or not, and to do so, it must have all the necessary signals.

[edit]
I browsed through it again a bit.
There's a Gateway Control Module (GRA) that communicates with the Message System Gateway (MSG) via CAN. However, this is only found in the PQ35 and PQ46 models, not in the Polo. Here, the entire GRA (Gearbox Remote Automation) control is handled via CAN (Controller Area Network).
Therefore, your path would likely be the 'traditional' one.
Please check if any MSG messages are missing on the CAN bus. (see above)
Best regards, Jochen.

Hi, I've finally gathered all the data for the "peculiar" built-in MSG.

The sticker says:
Bosch ME 7.5
B 261 634 519 --- 381/4518.SA
06A 906 032 AK --- S 280/17
SG Number: S0 15635 D

Question: To which vehicle does the physical MSG belong?

The diagnostic device (VAG-COM) says:
Control unit part number: 06A 906 032 TL
Component or version: NP24C90o.hex G *XN20
Software coding: 11500
"WVWZZZ6EZ5B00xxxx VWZ1Z0E276xxxx"
Sure, here is the translation of the text from German to English:

"1 error found:"
18045 - Data bus drive: Missing message from the electronic central control unit.
P1637 - 35-00 - -

Question: Which vehicle does the software in this MSG belong to?

I would still like to have a working GRA and am willing to pursue one of the paths I described earlier. Of course, I would also be interested in a new/better one?

By the way, the connection from the SET contact has been tested and is working correctly!

Thank you for your help!

Is there really no one here who actually knows about this? Actually, I just want to know who can "reprogram" ports on control units from CAN to analog.

You've already assigned the control units yourself, haven't you?
032 AK is a Sharan with engine code AWC, and 032 TL is a Polo with engine code BJX.

LowBlubbi wrote:

Is there really no one here who actually knows anything about this? Actually, I just want to know who can "reprogram" ports on control units from CAN to analog.

I find the "only" to be the most problematic.
Besides the fact that reprogramming the ME7.5 is a topic in itself, you would need...
a description of the software (scope of functionality) and the precise location of the software controls.
Feature fields in the dataset.
The simpler approach would be to use the original software of a vehicle with the same or...
to find a comparable engine (and standard GRA) and to bring this data up to date.
programming.

Have you, as suggested on several occasions, adjusted the levels at the SET input pin (number ???)?
Have you checked the measurements recently?

Best regards, Micha.

Thank you for the answers.

Quote:

You already assigned the control units yourself... 032 AK is a Sharan with engine code AWC, and 032 TL is a Polo with engine code BJX.

I wasn't sure because it's a motor from a test platform, and all those statements always seem to come from hearsay.

Quote:

The simpler approach would be to use the original software of a vehicle with the same or... to find a comparable engine (and standard GRA) and to achieve this level of performance. programming.

It's a software version of the BJX that comes standard with a GRA (presumably a specific type of software or feature). It's also unlocked... see the text above.

Quote:

By the way, the connection from the SET contact has been tested and is working correctly!

As I said...!

I don't think it's only via SET that it comes.

LowBlubbi wrote:

It's a software version of the BJX for which a GRA is standard. It is also unlocked... see the text above.

Then the question remains whether the AWC was combined with GRA, and if so, whether the Sharan had it.
It provides a signal with the same polarity.

Quote:

By the way, the connection from the SET contact has been tested and is okay!

Which pin on the ECU?
What is the voltage for each switch position?
What is the voltage at the STG pin when the GRA lever is disengaged?
During measurements with values from 1k to 10k, apply a load and, if necessary, measure against ground and 12V.

In the worst-case scenario, the input stage of the SET is not populated. Then, it would be necessary to solder the connection in the control unit.
"Another possibility is an incorrect polarity of the input stage (e.g.,..." Pull-up to 12V and the...
The switch also provides 12V. The STG would then be unable to distinguish between an open and a closed state.
Differentiate between switches.

Best regards, Micha.

I'm afraid you can forget about doing that with the BJX software (unless someone rewrites it).
The BJX was only installed in vehicles with an onboard network control unit (ECU), and the GRA signals were intended to be transmitted exclusively via CAN.
Why did you see something despite the MWB being at 66?
For example, the AWC does not have an onboard network control unit (ECU) installed. SET goes to pin 57, and the other two...
connected to lines 75 and 76.
If the wiring of the two motors is the same (excluding the GRA), then...
Could the AWC software be the solution to the puzzle? (If so, all you need to do is find someone who...)
that she programmed for you).

Best regards, Micha.