3AA920 880H SW 0505 HW H05

[mickyjenny]

That is good because I already paid for the cluster.
It's not easy to find a 3AA or 3C8 880 SW 0611 for a good price and the prices of 881 are even higher.
Thank you for your help.

[mickyjenny]

I finally received the cluster but the situation is getting complicated.
The first problem is that the new cluster has more than 190.000 KM and my old one 128.000 Km. As far I know just special tools can change the mileage to a lower amount, am I wrong?
The second problem is that the EEPROM is not a normal ST 24C64 but a Microchip Tecnology 24LC64. This EEPROM has a write protection so must be desoldered in order to read/write the content (in circuit pin 1-2-3-4 are shorted with pin 7). But is not a big issue, I will just lose more time to desolder it, save a backup, flash the new firmware, desolder it again, write the 881A EEPROM and solder it again.
Is it true that the radio code (that I don't have) is stored in the cluster EEPROM ( 0x1298-0x1299)?
How can I transfer my old mileage to the new cluster?
Thank you.

[skodapilot]

Keys are stored in MCU and is not external accessible, without VVDI2 or equipment like this, you have to desolder MCU

[mickyjenny]

You mean the mileage? Because the radio code is really stored in the EEPROM at the offset 1290 bit 8 and 9. I tried and it works, one problem is solved.

[mickyjenny]

I also solved the mileage problem, I took the car to a shop and they lost almost 3 hours because Obdstar X300 PRO and Diagprog4 asked for the smart key (that my passat doesn't have) to change the mileage. I had to took apart the cluster so that they could feel a section of the EEPROM with FF. Now I have the right mileage but a lot of errors. Tomorrow I will transfer the actual mileage to the last working EEPROM that I had (with an higher mileage but no errors at all and my old VIN number that I took from my original cluster: 0x12E1-0x-12F8, 0x13C0-0x13D7, 0x13D8-0x13E0F). Will be interesting to understand which address was causing the key request, this part is still something from the tiguan EEPROM that is not needed on the passat (for the 2d to 3d mod).

[mickyjenny]

The first part is done, I was able to get rid of all the errors caused after lowering the mileage. Coping just the mileage to my last working bin was not enough, the cluster starts in error mode (instead of the km you just see the error message and a lot of funny errors in VCDS, all without mileage indication). The reason is that in the EEPROM the mileage is stored in 3 different addresses:

0x12A0-0x12BF (Mileage)
0x12C7-0x12DE (Base mileage checksum)
0x14D0-0X14E7 (Duplication of the main mileage control)
*Update
0X14E8-0X14FF Must be changed too, is another duplication of the base mileage. I had no errors when I forgot to change it, but to be sure now I changed it too.

Just changing the first part: Error mode
First and second parts: The cluster shows the old mileage 193.000 (moment of fear, I thought I could not come back to 129.000)
First, second and third parts: Everything works, the right mileage is back (129.000) and no key request error after a while (this error first appeared after they messed with my EEPROM, filling it with FF... I don't know exactly which address).

I still would like to understand which address of the immo part is responsable for the key request by trying to lower the mileage with a special tool. I'm pretty sure that it's a mess that I did at the beginning:
I made no backup of the orginal 3AA920880P, thinking that I had to import just the content of my 3AA920780A to 38C920881A. A big mistake because you can not just import the immo part of a cluster to another cluster.
So I had to import the immo of the 3AA920880P backup to 38C920881A after flashing with the tiguan firmware. I made a backup of the EEPROM after the upgrade (has been recognised as 3AA920880P SW1104) and than I imported the immo part to 38C920881A. I think that during the tiguan flash some part of the eeprom (between address 0X12A0 and 0X14FF) has been overwritten with tiguan information (that I still have on my EEPROM), that's why when you try to lower the mileage with every tool will ask for the key (normal procedure for a tiguan).