2000 nissan almera 4door. wont start ,checked plugs , starter ok , petrol getting to engine

Question edited for clarity.
Question moved to model category.

Reset the security system and engine immobilizer. Connect a code reader scan tool as see what it shows.

https://www.google.com/search?q=2005+Nissan+Almera+reset+security

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check fuses and relays --check for power[ fuse ] to the port on quit a few vehicles usually the accessory fuse and obdll port are same ==the following link shows what pins to check with a meter if you have power to the port then start checking your harness,connections and computers
OBDII On Board Diagnostic System Does My Car Have OBD II The Connector...

look in the engine bay against the firewall to the right under below air filter box to throttle pipe usually cylindrical shape made of metal silver or black in colour

year/make/model will be needed for help

Code 345 means the cam sensor on bank two is not sending the correct signal to the engine computer. So no spark.
If you have replaced the sensor, the problem could be the cam or the wiring from the sensor to the computer.

2003 almera head gasket replaced car wouldn't start

I am having the same problem. I have changed my cam shaft sensor and though it has improved a little but the problem is still there, i've been told it could be the 'air flow meter'. I am having somebody check it out tonight (plugged into some computer to ID the problem)

Try a tune up and do a compression test to see if the engine is worn out. You may want to check your air cleaner as well.

It's located in the fuse box under your hood. Should be near the fender wall or the firewall

Solution #1 is not correct.. reason, why engine does not start when those codes are shown, is pump control unit (PCU), or electromagnetic valve. You should give PCU to fix (mostly it's broken transistor inside) or to change you current PCU to the new (need to be programed) or buy whole new VP44 PSG5 pump.
Sorry for my broken language :)