Citroen C3 2009 C1136 fault code ESP/ASR system faulty

[Palebow]

Hi,
I would be extremely thankful for any help regarding this ESP related problem.
The car is a CITROËN C3 II (SC_) 1.4 VTi 95 (70 kW / 95 hk) 2009 vin no VF7**************[VIN obfuscated, can be read by forum staff].

Brakes and steering works fine but there´s an ESP-light on the dash.
Got the fault code C1136 Permanent. Steering wheel angle sensor signal fault. Coherence.
When looking in my fault code reader it says the SAS is working fine..
Have tried calibrating the SAS which also works fine...but the code can´t be deleted...(I changed the steering column stalk and it made no difference)
All fuses and relays are good. (I have tried a different fusebox)

I read in another tread in this forum that there is a second sensor inside the steering rack...so I bought a second hand steering rack with the same article no 9671732080 from a C3 with vin no VF7**************[VIN obfuscated, can be read by forum staff] and installed it.
This caused a new problem...fault code U1221 Permanent. Absence of communication with the electric power steering ECU.
After changing the steering rack, calibration of the SAS is no longer an option in my fault code reader.

Questions:
1:Is there any way to reset and activate this second hand steering rack using Lexia or Diagbox? (I have acces to Lexia and Diagbox via a friend)or is this a dead end?

2: If not possible to use the second hand rack...how do I solve the problem?

[ozvtr]

I don't believe there is any sensor in the steering rack associated with the ESP.
The ESP works by comparing the Steering Angle Sensor in the COMs unit with the Gyro (Yaw angle sensor), typically located near the hand brake in the middle of the car. The "coherence" part of the error would be the difference between the SAS and the gyro.
It's possible that worn components in the front suspension had thrown the ESP out.
Did you get a wheel alignment done to check the suspension dynamics?
How did you perform the ESP calibration?

[Palebow]

Thanks a lot for the input ozvtr.
Wheel alignment have been done and the SAS was calibrated with Lexia.

The sensor in the steering rack I was refering to I believe is a torque and angle sensor...and as I have understood, in some vehicles (depending on its equipment...like semi-automatic parking assistance) the steering wheel angle sensor can be located either in the steering wheel controls or in the steering rack mechanism itself.

But you´re saying that in this case the SAS is in the steering wheel controls and not in the steering rack and that the problem is in the communication between the SAS and the Yaw angle sensor?
Then if the "coherence" part of the error is the difference between the SAS and the gyro...and the SAS is ok according to Lexia...then the problem should be the Yaw sensor or worn components in the suspension right?

The handling of the car is all good...is it still likely that worn components in the suspension is the reason for the ESP-light?