Faulty Glow Plugs: Causes & Solutions

hello,
"In my Audi A4 B8 2.0 TDI CR, all the glow plugs are defective. There's a constant voltage of 11.9 volts at the connector on the glow plug cables, even when the Audi is turned off. However, the glow plugs themselves require only 4.4 volts. Where is this high voltage coming from? Is the control unit defective?"

Constantly, i.e., even with a warm engine?
Do you ever get a car scan done?
hg
Herbert.

"Yes, even if the engine is warm, unfortunately, I don't have a VCDS."

That would be useful here!
hg
Herbert.