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Correct Displayed Speed SW1104

Posted: 07 Aug 2025 07:37
by heinlein
Hi,

I've retrofit the cluster 35D 920 880E HW02 SW1104 into a 2010 Passat R36. The new cluster is 3D Premium Colour, from Chinese Passat B7.

I copied the 300km/h speedo section from the 3C0 Cluster, and the needle shows the same as the digital display.

However, speed seems to be 10% higher than GPS.

I tried editing EEPROM address 0xAD, but it doesn't seem to have an effect on the displayed speed.

Would VDOeditor be able to fix this problem?

Re: Correct Displayed Speed SW1104

Posted: 20 Aug 2025 04:53
by heinlein
I ended up solving this issue. Below is a copy of what I posted on https://www.drive2.ru/b/597403426229324541/

I found that it didn't matter what value I put at 0xAD, the speed was always off by about 11%+ after importing my speedo data from the original 3C0 cluster. Odometer seemed to update accurately regardless of the value at 0xAD.

After some trial and error, I found that the both the digital speed display and speedometer data comes from the speedometer section of the EEPROM 0x79A-0x7D3.

As others have mentioned, the long coding byte 0 bits 0-3 cannot be changed, so changing the K-value in coding is not possible.

In order for the speed to display correctly (+5% by law), 0x79A-0x7A9 must be the same as 0x7AC-0x7B9, except for byte 0x79A which is C0.
0x7BA-0x7C9 controls needle position for the difference speeds in the previous two sections and is reflective of the scale layout.

For my 300km/h Passat R36 I have the following hex data for 0x79A-0x7D3.
C0 00 CD 02 00 0F 00 1E 00 32 00 5A 00 96 00 9B 00 00 CD 02 00 0F 00 1E 00 32 00 5A 00 96 00 9B 00 00 AF 00 74 03 D7 06 19 09 9C 0D 20 12 80 12 80 80 CB B6 AF A4 99 99 AA AA

Checksum data at 0x32E-0x32F is 3C A6 otherwise you get error on the odometer for these speedometer parameters.

Not sure if it affects anything, but I also updated 0xB2-0xB3 to E3 07 for 2019mm wheel diameter. 0xAE-0xAF to 34 53 for 21300 k-number. 0xAD is 04.