Hi, I have a 2005 Octavia 2 4x4 TDI with a second-generation Haldex. About six months ago, the ESP started turning off by itself. The mechanic told me that there is a problem with the entire Haldex system and that the Haldex control unit needs to be replaced. Mine has the number 1K0907554C. He said that this control unit must be replaced with an identical one with the exact same number. However, people say that it is possible to replace it with a unit with a different number, such as B or F, without the need for a software update. So, what is the truth? Because finding an identical number is practically impossible.

My son in law is having problems as well. Try this https://www.haldexrepairs.co.uk/guide-generation-4-haldex-trouble-shooting/

Theres a lot of useful info on their site. One thing to check is the condition of the Haldex controler wiring socket. They can get coroded and send false signals to pump etc. The ecu for the haldex can also suffer from water ingress which causes similar symptoms as the circuit board can corode to. They can repair them as well if I remember.

Alasdair