Where crank shaft and camshaft?

Here's a video on your sensor,this vehicle's engine is the same as your's. Replace Nissan 3 5L V6 Crankshaft Position Sensor

there is only one crankshaft sensor so you will be looking for a CAM shaft sensor for it to be on bank 2
go google and type in --location of cam shaft sensors on nissan altima engine ---

These are a well known failure point for this vehicle and engine. They are currently on there third redesign to help solve the frequent failures.

the first thing to do is see if there are any trouble codes in the computer. If you see P0340

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

follow this link it shows a great pic of its location.
http://www.paulstravelpictures.com/Nissan-Altima-Camshaft-Crankshaft-Sensors/Altima-Crankshaft-Camshaft-Sensor-Replacement-038.html

Here's some pics of my 2003 Altima Crankshaft Sensor. Often mistaken by the Camshaft Sensor because both are identical sensors. They are each located in different locations. I've seen diagrams with the WRONG labeling. Again, this is so confusing for even a mechanic to understand because both sensors carry the same part number which is rare. http://x.nissanhelp.com/forums/members/digitaldxing-albums-2003-nissan-altima-crankshaft-position-sensor-picture331-2003-nissan-altima-crankshaft-position-sensor.html

In the kit there are two sensor that look identical. The one for the crankshaft has a white paint mark on it near the bolt hole. Make sure that it is in the right location.

Crankshaft and Camshaft Position Sensors Camshaft Position Sensor Engine timing is determined from the relationship between the crankshaft and camshaft. This relationship is maintained by a timing chain or timing belt. The Engine Management System does not control engine timing but it does monitor the relative position and speed of these shafts by monitoring signals generated by sensors. The Engine Management System (EMS) uses signals generated by the camshaft position sensor to synchronize fuel injection to the valve sequence and for the on-board diagnostic procedure for misfire detection. The EMS energizes the injector at or near the time the intake valve opens. For misfire diagnosis, the EMS compares the number of camshaft sensor reference pulses and the number of crankshaft position sensor reference pulses received. If the EMS receives an incorrect number of pulses Diagnostic Trouble Codes (DTC’s) should be stored in the EMS.
If the camshaft position sensor or circuit is faulty most engines will start. Some engine management systems will then default to a pre-programmed injector firing sequence. All injectors may be energized simultaneously or all of the injectors on one bank may be energized at the same time. If the CMP data is required for misfire detection and reliable CMP data is not present misfire detection would probably be suspended.
Related Symptoms The following symptoms can be caused by an intermittent wiring connection or faulty signal to the EMS:

• Extended crank time with a cold engine
• Intermittent rough running
• Unstable idle
• Bucking
• Hesitation
• Stumble
• Chuggle
• Poor fuel economy
• Stalling on acceleration

Crankshaft Position Sensor Engine speed is a very important input to the Engine Management System (EMS). Crankshaft speed and position are the basis for many calculations made by the computer. Crankshaft position values are transmitted to the computer by pickup coils also known as Permanent Magnet (P/M) generators, hall-effect sensors or optical sensors. The Crankshaft Position Sensor (CKP) also known as engine speed sensor is located in close proximity to the crankshaft.
In addition the EMS uses minute variations in the CKP sensor data to determine engine misfire. The EMS uses this information in conjunction with the camshaft position sensor to perform misfire diagnostics.
Related Symptoms: No Start/Intermittent Start Condition – Can be caused by a faulty crankshaft position sensor due to loose connections, bad grounds, high resistance in the circuit, or opens in the circuit

There are two cam shaft sensors and one crank sensor Nissian did sell a kit at one time with all the sensors in it one cam sensor is in the left cylinder head a one is in the right cylinder head

1st, Nissan had a recall on Crank position sensors for 2002-2006 Altima's. Check with you dealer before you go doing any repairs. You may discover you can get your car repaired at no charge.
NHTSA Campaign ID number :O7V527000
Symptom: Erratic behavior. Stalling and no starts and very difficult to diagnose due to the time frame in which the component actually malfunctions. The warranty should not be limited to the original owner.
I would also need more specifics as to which engine you have so I might assist you in where the location of the sensor is. The Altima had a 4 and a 6 cyl engine offered that year.

I have 10 years experience in a Nissan dealership and I know without a shadow of a doubt that the Crankshaft Position Sensor is NOT located next tp the crank pulley... it is rather at the other end of the engine near where the transmission bellhousing bolts to the engine block. It is on the side toward the firewall near the bottom. Even if you can get the vehicle on a lift and get under it, you can't really see it... It's more of a feel thing... There was a campaign (recall) on these engines to replace Crank Position and also Cam Postion sensors. Check with your dealer- the campaign might be open. You will need your VIN number when you call.