Location of knock sensor on 98 sentra 2L

Plugged catalytic converter.

Have the charging system thoroughly tested and make sure the diodes in the alternator are good . Make sure all grounds , especially PCM grounds are good . Multiple codes are sometimes caused by bad grounds or charging system interference .

Melvia, Knock sensor located under the intake manifold between cylinder #2-3 I believe, hard to change with out removing intake manifold, but can be done. Check the attached links,instruction and guides, Good luck
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If you had code P0305, I don't know why they would have done anything to the #2 cylinder but if they have already replaced the plugs, wires and injector; here are a few more items to check:
1) Check connections from ECM. Look for any corrosions or bent/broken pins.
2) Check the fuel line pressure
3) Check the engine compression
4) And if the above are good, then you will probably have a defective ECM

171 Sys lean bank 1 possibly o2 sensor 300, cyl misfire detected random cyl. 302 misfire cyl # 2. 304 cyl misfire cyl #4 with all 3 of these codes it might be time for new spark plugs and wires

Dude you just got ripd hard . He's obviously 1 of those garages that do that to people

run a compression test to check for loose valve seat insert . no 1 cylinder
other wise it is a fuel pressure problem and faulty injector/s

go have your catalatic converter checked, it may be plugged causing your car to suffocate when you accelerate

take sample of your fuel into clear plastic bottle from fuel line
is there any water present?
this can cause these codes and then not go on storing codes for other bank even though that bank will be missfiring also due to water & P0300 Random/Multiple Cylinder Misfire Detected being logged
check all connections to coils/leads & wiring connectors
due to miss fire codes for cyl 1,3,5 all on the same bank
also look and check for air leaks on that bank (hose knocked off or splithose)inlet manifold gasket,brake booster etc...
3 injectors being blocked slightly on same bank posible!!!
check wires and signal

was it running like this b4 tune up & repairs?
this is what codes are
P0170 Fuel Trim Malfunction (Bank 1)
P0300 Random/Multiple Cylinder Misfire Detected
P0301 Cylinder 1 Misfire Detected
P0303 Cylinder 3 Misfire Detected
P0305 Cylinder 5 Misfire Detected

the last code is for trans due to misfire/running lean on bank 1 probably a torque problem code

Look for broke/ shorted wires on Crank sensor.. thanks