My nissan sentra 2005 special edition does not rev. when i change the brain box it revs alright. i opened the brain brain box trying to fix it then i realised water has entered, i cleaned it but still does not work.

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If it's an automatic, is there fluid in the transmission? If the fluid is ok, the transmission is bad. If it's a straight stick, the clutch is bad.

There's a free download copy on "www.courtesyparts.com/pdf/2005-Nissan-Sentra.pdf"

Your first order of business is to check the oil level in the crankcase, and bring it up to full level. You can probably find a replacement dip stick, or go to a junkyard and get one. Without sufficient oil in the engine, The will seize. or prematurely die.
Is your check oil light coming on? Have the car scanned for trouble codes. Auto Zone and Advance Auto will a scan. Then you will be able to get info on the codes and what they identify. Just look the codes up on an internet search.

Not generally, unless the engine's been run hot, if even only for a moment. If the head gasket is blown prepare for major out of pocket expenses because if the engine overheated it will bend every valve and usually warp the head beyond repair. I honestly hope this is not your problem, it's an extremely expensive fix. Hope this helps, good luck!

drain and fill trans with fresh fluid
trans may have to be rebuilt

sorry

IT CAN BE YOUR ECM CONNECTION

It appears the car may not be entering tuneup mode. warm up until temp is normal, idle stays below 1000 rpm
2000 rpm for 2 minutes
rev engine 2-3K three times
idle for one minute
turn off
disconnect tps
start
rev 2-3K three times
adjust timing

a noise in the engine is not a good news but you have 70% chance that you engine crank shaft and parts arround it are bad. in some case if your car is auttomatic ,a crack in the flight weell may cause the "knocking sound " please ck you fly w before you make decisions .if you engine is bad ..,, change it .it will cost you more to try to fix it