A little more info would be helpful. There's only six diifferant model Sentra's. This might help.
Vehicle Application: 1994 Nissan Sentra SE 1.6L, Vin E, Eng Des GA16DE 1994 Nissan Sentra XE 1.6L
Customer Concern: No start. No spark. Tests/Procedures: 1. Check the pulse signal to the base of the power transistor on the White wire in the 3-pin connector at the power transistor when cranking. The voltage should be 0.3 to 0.6 volts (average on time voltage). If checking with a scope, expect to see a 0 to 2.0 - 4.0 volt saw tooth pulse signal.
2. If OK, then the distributor's optical sensors are working and the coil power transistor unit is the most likely problem. Check for 12 volts on coil negative key on and for a pulse signal to ground while cranking.
3. If the signal on the White wire to the power transistor is not good, then check the Camshaft Position (CMP) sensor located inside the distributor. At the 4-pin connector at the distributor, disconnect it and measure the voltage on all 4 pins - look for battery voltage on the Orange/Blue wire, 5.0 volts on the Blue wire and 5.0 volts on the Yellow wire, and a ground on the Black wire.
4. Connect the distributor connector and crank the engine while measuring the voltage - the Yellow wire should have approximately 2.4 - 2.7 volts and the Blue wire should approximately 0.2 - 0.5 volts (average on-time voltage). If checking with a scope, the Yellow wire should have a 0-5 volt square wave signal every 1 degree of crankshaft rotation and the Blue wire should have a 0-5 volt square wave signal every 180 degrees of crankshaft rotation with 3 narrow signals and one wide signal with the wide signal denoting cylinder #1. If the 5.0 volt reference is present with the distributor connector unplugged and key ON, but there are no square waves with the distributor connector plugged in and back probing and cranking, and the distributor battery voltage and ground are good, then the distributor is the problem.
5. If the distributor checks out OK but there is no pulse signal to the power transistor, check the White wire from pin 1 at the Engine Control Module (ECM) for shorts to ground or an open circuit. Potential Causes: Coil Distributor Electronic Control Module (ECM) Power Transistor Wiring