Awe mense. I have a serious problem. My citi golf was at workshop and needed key coding due to immobilizer not recognizing the transponder. So the guys at the workshop ended up taking out my original computer box and inserted their bypass box to start and move the car in and out of the garage. So now, the electrician coded the key and cluster, tested the key and the error was removed but the computer box was not plugged. Cool, then plugged in the bypass box and started the car with no error on dashboard. So after the electrician tested multiple times, it was working just fine. So the workshop guys only realized later that they plugged the wrong box and put in the correct one. Now the immobilizer error is back, so how do I fix this

Hi
If I remember right you need to code the ECU and Cluster to the new key.
So that needs to be done.

So I managed to fix it by basically just plugging in the correct computer box and put the key in the ignition and switched it on without starting it. We towed the car and magically after 30 mins the key coded itself and removed the key error on the dashboard. We pulled aside and started the car and it actually started. Switched it off and started it again and it worked perfectly until today. Even the spare key works without any problems.