Just replaced the rack n pinion on the Civic si.

Never heard of any issues with the racks on them

is the fluid full?

Why did you replace it

Where is the noise coming from?
Does it occur when you turn the steering with front end lifted up?
Who installed the steering and was everything fitted correctly?

Roy

The DTCs are memorized in the EEPROM (nonvolatile memory) therefore the memorized DTCs cannot be erased by disconnecting the battery.

You would need the appropriate scan tool to clear DTCs.
Roy

How to Troubleshoot DTCs
The troubleshooting procedures assume that the cause of the problem is still present and the EPS indicator is still on, Following the procedure when the EPS indicator does not come on can result in incorrect diagnosis.

Question the customer about the conditions when the problem occurred, and try to reproduce the same conditions for troubleshooting. Find out when the EPS indicator came on, such as during EPS control, after EPS control, when the vehicle was at a certain speed, etc.
When the EPS indicator does not come on during the test-drive, but troubleshooting is done based on the DTC, check for loose connectors, poor terminal contact, etc, in the affected circuit before you start troubleshooting.
After troubleshooting, clear the DTC and test-drive the vehicle. Be sure the EPS indicator does not come on.

Did you have any codes from this system?

If the motor fails, it will cause no assist. Did the motor come with the used rack?

I also attached a wiring diagram as well.

Roy

The problem could be with the rack but first of all you need to get the Indicator light off first. When it is showing, the system is not going to work correctly untill at least a few runs.

Try turning the steering with engine off, does it make any difference?

Roy