What could be the cause of this error?
Citroen C4 2017 MoreLife - engine 1.2 PureTech.
I had issues with my AC and went to have that checked out. The mechanic told me I could pay more by refilling R1234yf or less by replacing it with 134a. I went with the cheaper option and had no problems for a few hours, and my cooling seems to have been fixed.
I went to the store later that day, but when I started my car after leaving the store, I had the "Electrical circuit system: repair needed" message on the screen. It appeared again after restarting the engine.
I drove back home, and the error persisted. I checked with OBD2, but no errors were found. Engine voltage is at 12.5V while off, and it charges to 13.95V after turning it on.
Eventually it disappeared, but appeared again today.
Same situation - started the engine with no error, drove to my destination, turned the car off and returned after 30 minutes and turned it on - the error appears.
It only appears on startup - either just the system or the engine as well. Never appeared while driving.
Also, car battery was replaced once by previous owner in October 2025.
I tried moving the AC sensor around, but it did not solve the issue.
Can it be related to switching the cooling gas, or could it be a different issue entirely?
I included the pictures showing the error and which part of the car the mechanic was working on.