The solution below shows the Nokia X3 pin connector connection line paths through to a particular components that holds the SIM card to work. Just refer to the solution to trace each corresponding pin connection for a quick and easy troubleshooting or repair.
Nokia X3 Insert SIM card Solution
You may first check the SIM supply voltage (VSIM) pin and ground pins, then the SIM Clock pin. The SIM Data and the SIM Reset were directly connected to the PEARL IC, tracing this line paths may need to remove the PEARL IC first.You may also try to replace the capacitors and resistors being connected to it.
So, if the three pin such as VSIM, Ground and SIM clock line paths were all both okay.
The last and only option is to rework the pearl IC or replace if necessary if the Nokia X3 still shows insert SIM card or does not detect the SIM card.