Where is the ckp sensor located on a 2004 chevy venture 3.4

I don't know if you can get at it from engine compartment? On some vehicles, I safely raise and support the vehicle, then remove passenger side tire to see if it is easier to get at? It just depends on what is the easiest for you? Note, when working under a vehicle there are safety issues, safety is your responsibility.

This answer covers 1999-2005 Cadillac Deville, Eldorado & Seville.
Example Engine:
2002 Cadillac Seville STS 4.6L SFI DOHC HO 8cyl.

This engine has (2) Crankshaft Position (CKP) Sensors: the Upper sensor is CKP sensor B, and the lower sensor is CKP sensor A (this is included for the OBD-II DTC codes - P0385 references Sensor B = upper CKP sensor, whereas P0335 references the lower CKP sensor (sensor A)).

Both crankshaft position sensors are located in the front of the engine just above the oil filter adapter. To access both CKP sensors, jack up vehicle on the passenger side, remove the oil filter, and the oil filter adapter, including the Engine Oil Pressure (EOP) switch. See illustration.

The ARROW points toward Front of Car.
1. Upper Crankshaft Position Sensor (B).
2. Lower Crankshaft Position Sensor (A)
3. Engine Oil Pressure (EOP) switch
4. Engine Oil Level switch
The Oil Filter is the can-type object below the oil filter adapter, which includes the EOP switch. Recommend: remove oil filter with an oil filter socket/strap wrench, since it's close to the oil pan.

If it has one it would be on the bottom of the radiator. Most cars and trucks today don't have a plug or valve.
You are expected to use a recycling machine to flush the coolant.

fuel filter,dirty throtle body,air filter,IACV.

It's the oxygen sensor screwed into exhaust manifold on driver side.

On most Chevys look under the drivers side floor board on the inside of the chassis

WHAT CKP SENSOR DID YOU REPLACE I BELIEVE THE SEDONA 3.5L ENGINES HAS 2 CKP SENSORS.YOU HAVE ONE CKP SENSOR LOCATED FRONT OF ENGINE ON THE OIL PAN MOUNTED BEHIND CRANKSHAFT PULLEY AND THE OTHER CKP SENSOR LOCATED NEAR THE TRANSMISSION BELLHOUSING. CHECK TO SEE IF YOU HAVE CKP SENSORS. IF NOT CKP SENSOR WIRE COULD BE DAMAGED.ALSO CHECK TO MAKE SURE BATTERY POWER GOING TO CKP SENSOR B PLUS WIRE IF NOT CHECK THE ECCS RELAY OR FUSES MAKE SURE POWER IS GOING TO CKP POSITION SENSOR

Should be close to the thermostat housing.

located in thermostat housing or in intake nearby (where top hose connects from radiator to engine)

It is a 2 wire seneor under the throttle body. You will have to remove the air breather and it will be a brass/black plastic sensor. A 3/4 socket will fit it.Good Luck