Where is the knock sensor located on a 2002 nissan maxima

Check engine light on ? What code ? There are many different (DTC'S) - diagnostic trouble codes that can set for knock sensors ! There all don't mean that you replace the sensor .
DTC P0324: Knock Sensor (KS) Module Performance
DTC P0325: Knock Sensor (KS) Circuit Bank 1
DTC P0326: Knock Sensor (KS) Performance
DTC P0327: Knock Sensor (KS) Circuit Low Bank 1
DTC P0328: Knock Sensor (KS) Circuit High Bank 1
DTC P0330: Knock Sensor (KS) Circuit Bank 2
DTC P0332: Knock Sensor (KS) Circuit Low Bank 2
DTC P0333: Knock Sensor (KS) Circuit High Bank 2

The knock sensor (KS) system enables the control module to control the ignition timing for the best possible performance while protecting the engine from potentially damaging levels of detonation. The sensors are located below each cylinder head on the engine block. The KS produces an AC voltage signal that varies depending on the vibration level during engine operation. The control module adjusts the spark timing based on the amplitude and the frequency of the KS signal. The control module receives the KS signal through 2 isolated signal circuits. The control module learns a minimum KS noise level at idle and uses calibrated values for the rest of the RPM range. The control module should monitor a normal KS signal within the noise channel.
Knock Sensor Replacement - Bank 1
Remove the exhaust manifold lower heat shield. Refer to Exhaust Manifold Lower Heat Shield Replacement.
Disconnect the engine wiring harness electrical connector (1) from the bank 1 knock sensor (2).
Loosen the knock sensor bolt and remove the knock sensor.
Knock Sensor Replacement - Bank 2
Disconnect the negative battery cable. Refer to Battery Negative Cable Disconnection and Connection .
Remove the engine oil filter. Refer to Engine Oil and Oil Filter Replacement .
Lower the vehicle.
Disconnect the engine wiring harness electrical connector (2) from the bank 2 knock sensor (3).
Loosen the knock sensor bolt and remove the knock sensor.

Did you change the correct knock sensor? You may have other problems that the knock sensor is detecting, which means the knock sensor is operating correctly. Knock is usually caused by detonation (cylinder firing before intended). There are many reasons this can happen. A common one, is the cylinder is running too lean.
http://www.obd-codes.com/p0328
https://en.wikipedia.org/wiki/Engine_knocking

the following information courtesy of OBD-CODES.com P0328 Knock Sensor Circuit High Input OBD-II Trouble Code Technical Description Knock Sensor 1 Circuit High Input (Bank 1 or Single Sensor) What does that mean? Knock sensors are used to detect engine pre-detonation (engine knock or ping). The knock sensor (KS) is usually a two wire sensor. A 5 volt reference is supplied to the sensor and there is a signal return from the knock sensor to the PCM (powertrain control module). The sensor signal wire informs the PCM when a knock occurs and in what degree of severity. The PCM will retard the spark timing to avoid pre-detonation. Most PCMs have the ability to learn spark knock trends in the engine during normal operation. A P0328 code is a generic DTC, thus it applies to all makes of vehicles, and refers to a high output voltage of the knock sensor. In many cases, this means the voltage is above 4.5V but that specific value depends on the specific make and model of vehicle. This code refers to the sensor on bank #1. Symptoms Symptoms of a P0328 DTC may include: MIL (Malfunction Indicator Lamp) illumination Audible knocking from the engine compartment Pinging from engine under acceleration Loss of power Irregular RPM Causes Potential causes of a P0328 code include: Knock sensor connector is damaged Knock sensor circuit is open or shorted to ground Knock sensor circuit is shorted to voltage Knock sensor has failed Loose knock sensor Electrical interference in circuit Low fuel pressure Incorrect fuel octane Mechanical engine problem Failed/faulty PCM Possible Solutions If you can hear engine knock (detonation), first fix the source of the mechanical problem and retest. Ensure the correct octane fuel was used (some engines require premium fuel, check the owners manual). Aside from that, for this code, most likely the problem will lie either with the knock sensor itself or the wiring & connectors going from the sensor to the PCM. Realisitcally, for the DIY vehicle owner, the best next steps are to measure the resistance between the two knock sensor wire terminals where they go into the PCM. Also, check the voltage of the same terminals. Compare those numbers to the manufacturer's specifications. Also, check all wiring and connectors leading from the knock sensor back to the PCM. In addition, you should also check the resistance using a Digital Volt Ohm Meter (DVOM) of the knock sensor itself, compare it to the vehicle manufacturers specification. If the knock sensor resistance value is out of spec, then it needs to be replaced. Other knock sensor DTCs include P0324, P0325, P0326, P0327, P0328, P0329, P0330, P0331, P0332, P0334 Register now to ask a question (free) Related P0328 DTC Discussions

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P0325 Knock Sensor 1 Circuit (Bank 1 or Single Sensor) -Circuit Malfunction
P0326 Knock Sensor 1 Circuit Range/Performance (Bank 1 or Single Sensor)
P0327 Knock Sensor 1 Circuit Low Input (Bank 1 or Single Sensor)
P0328 Knock Sensor 1 Circuit High Input (Bank 1 or Single Sensor)
P0329 Knock Sensor 1 Circuit Input Intermittent (Bank 1 or Single Sensor)
P0330 Knock Sensor 2 Circuit (Bank 2) -Circuit Malfunction
P0331 Knock Sensor 2 Circuit Range/Performance (Bank 2)
P0332 Knock Sensor 2 Circuit Low Input (Bank 2)
P0333 Knock Sensor 2 Circuit High Input (Bank 2)
P0334 Knock Sensor 2 Circuit Input Intermittent (Bank 2)
P0335 Crankshaft Position Sensor -Circuit Malfunction
P0336 Crankshaft Position Sensor -Range/Performance
P0337 Crankshaft Position Sensor -Low Input
P0338 Crankshaft Position Sensor -High Input
P0339 Crankshaft Position Sensor -Intermittent
P0340 Camshaft Position Sensor A Circuit (Bank 1 or Single Sensor) -Circuit Malfunction
sorry would a play with this to know for sure ,check the wiring plugs onto the sensors to make sure their not full of oil or corroded

P0328 Knock Sensor 1 Circuit High Input (Bank 1 or Single Sensor) knock sensor

Trouble Code: P0328

Knock Sensor Circuit High Input (Bank 1)

Possible Causes:


Knock sensor signal circuit is open.Knock sensor signal circuit is shorted to VREF or system power.Knock sensor is damaged or has failed.Trouble Code: P0420

Catalyst Efficiency Below Normal (Bank 1)

Possible Causes:


Air leaks at the exhaust manifold or in the exhaust pipes.Catalytic converter is damaged, contaminated or has failed.Front HO2S or rear HO2S is contaminated with fuel or moisture.Front HO2S and/or the rear HO2S is loose in the mounting hole.Front HO2S older (aged) than the rear HO2S (HO2S is lazy).

P0328 Is knock sensor code,all Nissan have this code so leave,concentrate on P0101 and P0103 this is MAF(mass airflow),Just make sure the timing belt is in good condition and the marks are correct, your solution is NTB02-003A In other word you need a reprogram on the ECM

Here you go John:

http://www.nissanhelp.com/diy/obd_codes/p0127.htm

http://www.nissanhelp.com/diy/obd_codes/p0328.htm

Code P0325 Knock sensor 1 circuit malfunction (bank 1 or single sensor)

Here you go:
P0305 Cylinder 5 Misfire Detected
P0325 Knock Sensor 1 Circuit Malfunction (Bank 1 or Single Sensor)

The 305 is most likely caused by a faulty knock sensor.(325)