The solution below shows the connection line paths of the two white LED's which is more convenient in tracing broken spots. It also shows which nearby particular components it is being connected or part of the keypad back lighting circuit.
Here's the some hints that may preferably help fix in troubleshooting Nokia C2-03 keypad back light failure.
1. Check the whole area and surrounding components for the keypad white LED for possible damaged, cracks, oxidation etc. Clean it first if necessary.
2. Check both of the two LED's using a multimeter. Replaced if already damaged.
3. If the LED's light are still working check the (VBAT 3.7V) battery voltage line paths.
|Nokia C2-03,C2-06,C2-08 Keypad light problem Solution|
5. Check the connected resistors and coils, re-solder or replace if damaged
6. Check the LED driver transistors. Re-work or replace if necessary.
View larger picture here.
This solution may also works on Nokia C2-06 and Nokia C2-08 since they both similar PCB board layout with Nokia C2-03 a Dual SIM card built in capability and a slider phone.