Fault Code P24AC 1.7 CDTI

[bubble12]

Hi,

I have a 2011 Astra J 1.7 CDTI 96 kW A17DTF ecoflex and one Fault Code P24AC.
EGR Valve is fine. And also EGR Cooler Bypass Solenoid Valve.

There are no power problems with the engine. 
If I reset the P24AC, after some minutes it is set again and I get the message "Service Vehicle Soon"

Where does this Fault Code come from. 
I found in Internet only "P24AC EGR Cooler Coolant Pump Feedback Circuit Low"
But I think my Astra does not have a EGR Coolant Pump.

Maybe somebody could help me.

Thanks

Stephan