Coding a used odometer, login code unknown...

Hi! Hi everyone, I'm new to the forum!

I have a problem:
I recently bought a used speedometer for my T4 on eBlub. Following the motto "Blue makes you happy," I wanted to install a blue speedometer in my 1996 T4 TDI (ACV), as the green one has a problem with the fuel gauge. Everything seemed fine, so I soldered a wiring harness, and everything worked except the tachometer. When I first started the engine, it went below the 0 mark and then stopped at the 6 o'clock position above the digital clock. It reacts to the engine speed, but only goes up to just before the 0 mark. It should also be noted that this is a blue unit without a CAN bus (part number 7D0 920 800 BX), as a 1996 T4 model did not yet have a CAN bus system.

I have now read the coding using VAG-Com 8.05. "00121" is programmed. Okay:

00 no additional equipment (correct).
1 Europe (incorrect, should be 0 for Germany)
Translation: Speed: 2.99 (incorrect, should be 4 for a 5-cylinder engine).
1. Departure impulse count: 3355 (incorrect, should be 2 for ACV with a shifting gearbox).

I would therefore need to encode it as "00042".

Furthermore, the mileage is incorrect; the odometer shows approximately 100,000 km less than the actual mileage of my bus, so it needs to be adjusted upwards.

I contacted the seller, but he couldn't provide any more information about which bus the speedometer came from, so he couldn't give me a vehicle identification number or anything like that. So, I can't ask "Freundlicher" for the login code either, right?

What can be done now to code this speedometer? I can probably live with the mileage, but the tachometer should definitely work. Also, the oil pressure warning light is constantly flashing, and the speedometer is beeping. Without a working tachometer, the oil pressure control, which is dependent on the engine speed, is malfunctioning. It only settles down and becomes quiet after approximately 2500 RPM; when I release the accelerator, the beeping and flashing starts again.

The blue dashboards without CAN bus are quite rare, as they were only installed for a few months before all T4s had CAN bus systems. Trying to find another account where the login code is known will likely be problematic.

Does anyone have a tip for me?


Best regards,
Nobbi.

The tachograph does not require a login code. In the T4 system, the WFS (Workforce Management System) is configured externally. To encode, you only need to use a plausible encoding method, and then it will work.


You can find tips and tricks on how to change a green dashboard to a blue one in the T4 forum. Sure, here's the translation:

'Here's the whole thing with instructions.'

Even there, use the search function!

Hi,


What can we do now to code this speedometer?
Ignoring the mileage, simply code it; no login is required -> Function 07 'Code the control unit'.


'Also, now the oil warning light is constantly flashing, and the Tachi is beeping.' Without the speed, the speed-dependent oil pressure control malfunctions.
The speed also plays a role. However, it's important to note that the new speedometer only uses a single oil pressure switch (with slightly different switching thresholds). Your T4 has two oil pressure switches.

Hello!

Thanks for the tips. I didn't know that the codes changed in 1999. I tried to re-encode the KI, but I only got an error message. That's why I thought I had to enter a login code to be able to encode it. However, I probably entered a code according to the old encoding scheme, which the KI couldn't understand. I'll try encoding it using the new scheme later. It will work out.

CU,
Nobbi.

Code:

xxx919xxx: ohne MotorCAN xxx920xxx: mit MotorCAN

It should also be noted that this is a blue unit without a CAN bus (7D0 920 800 BX), as a 1996 T4 did not yet have a CAN bus.

Nobbi wrote:

I might be wrong, but according to the part number, your AI has a CAN interface.

"800" likely refers to an older AI model from the 7D0 series. However, it's probable that these models can still receive discrete signals. Log into control unit 19 (CAN gateway) and set the value to 0. If the value is already 0, simply confirm and save. Then the CAN gateway will re-enter learning mode.

Regards,
Axel.

Hi,

xxx919xxx: ohne MotorCAN
xxx920xxx: mit MotorCAN
I might be wrong, but according to the part number, your AI has a CAN interface.


For the T4:
919 -> green light.
920 -> blue lighting
'xxx xxx xx0' typically, as in this case, indicates 'without CAN-Bus.'

Hello!

@axmax:
The AI model definitely doesn't have CAN (Controller Area Network). However, it's the only one of the blue models that lacks it. It was the very first blue model and was only produced for less than a year; all other models have CAN. I had it programmed a little while ago, and now the tachometer is working correctly.

The T4 has a confusing setup. The statement "xxx919xxx without CAN, xxx920xxx with CAN" is incorrect. What is correct is: if the last digit of the part number is zero, it's without CAN; if the last digit is 1, 2, or 3, it's with CAN. I don't understand why they didn't solve it the same way as they did with the Golf or Passat.


@UdoZ:
You're right. I've already replaced the corresponding oil pressure switch, the second one is simply not connected anymore. The oil pressure warning was only triggered due to the low engine speed; since the reprogramming, the oil pressure warning has finally stopped.


To everyone:
However, I still have one problem: The last digit of the code (the momentum number) cannot be changed. It is currently set to 1, so the code would be 3355, which is incorrect for the transmission in my ACV. Unfortunately, I cannot change this digit. If I enter anything other than 1, the encoding fails, and the entered code is simply not accepted.

Here's a list:

xxxx?: Coding number for the "Wegimpulszahl" (pulse count) (05/1999-04/2000):

1 - 3355 (all other engine/transmission combinations)
2 - 3407 (2.5L/75kW ACV/AUF engine with manual transmission).
3 - 3523 (2.5L / 75kW ACV/AUF engine, manual transmission, and Syncro).
4 - 3465 (2.5L/111kW AHY engine with manual transmission and 16-inch suspension).

xxxx?: Coding number for impulse duration (since 05/2000):

1 - 3355 (all other engine/transmission combinations)
2 - 3407 (2.5L/75kW ACV/AUF engine with manual transmission).
3 - 3523 (2.5L / 75kW ACV/AUF engine, manual transmission, and Syncro).
4 - 3465 (2.5L/111kW AHY engine with manual transmission and 16-inch suspension).
5 - 3300 (2.8L/150kW engine with manual transmission).
6 - 3325
7 - 3500
8 - 3550

I need to enter a "2" there, but the AI doesn't accept it. Could it be that the initial velocity value cannot be changed if the speedometer is not in the new mode? It would also be considered odometer tampering because it would result in the car accumulating kilometers at a faster or slower rate than it actually traveled.

Does anyone have an idea? Or, to put it bluntly: Does anyone in the Middle Hesse region perhaps have a VAGdashCom device that they could use to read out my login code, or put the speedometer into a new mode? While I could disassemble the AI, remove the EEPROM, and use a hex editor to set the new mode, I'm not in the mood to do that.

I don't want to do anything illegal. I just replaced my faulty instrument cluster with a used one. Now, I simply want to adjust the wheel speed sensor to match my transmission. Also, the instrument cluster shows 100,000 km less than the actual mileage. I don't want to tamper with the mileage (which is of course illegal), but rather increase it (I want the odometer to display the correct mileage of my car). I can also bring my old instrument cluster so you can verify my statement about the mileage. I'm not willing to pay a fortune for that, and I don't want to have to hire someone to tamper with the speedometer just to get it done.

Please, please, please...


See you then.
Nobbi.

The momentum value is usually stored somewhere in the EEPROM. If you want, we can try to find and change them. (without using AI to break them down) I also live only about 30km away from you . You can send me a private message.