How many o2 sensor on a 2000 i30 - 2007 Infiniti I35

Question edited for clarity and toss in some CAPS.

There is nothing that backs up memory. When you disconnect the battery, all memory is lost, which is why it is important not to do it!

You don't tell us the model? Is it a secret? All questions need 'year make model' as the FIRST 3 words.

If your have a 1999 Infinity I30, the ECM Fuse is Fuse 58.

58 10 Engine Control Module (ECCS), Mass Air Flow Sensor, Crankshaft Position Sensor, Idle Air Control Valve (IACV-ACC) Solenoid Valve, Ignition Coils, EGR, EGR Volume Control Valve, EVAP Control System Pressure Sensor

Infiniti i30 (A32; 1995-1999) fuses and relays

Fuse Box Diagrams https://fuse-box.info > infiniti > infiniti-i30-a32-1995-...

Fuse box diagrams (location and assignment of electrical fuses and relays) Infiniti i30 (A32; 1995, 1996, 1997, 1998, 1999).

Infiniti i30, i35 (A33; 1998-2004) fuses and relays

Fuse Box Diagrams https://fuse-box.info > infiniti > infiniti-i30-i35-a33-1...

Fuse box diagrams (location and assignment of electrical fuses and relays) Infiniti i30 / i35 (A33; 1998, 1999, 2000, 2001, 2002, 2003, 2004).

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Help in the link

P0720 2000 INFINITI I30 Code Vehicle Speed Sensor

https://www.autocodes.com > p0720_2000_infiniti_i30
Diagnostic trouble code is detected when Transmission Control Module (TCM) does not receive the proper voltage signal from the sensor. 'What are P0720 2000 ...
Missing: miss ‎' Must include: miss

More here

https://www.google.com/search?q=2000+infiniti+I30+miss+shifting+code+P0720

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code p 0134 refers to heated oxygen sensor(HO2S) 1 bank 1--no activity detected ===causes wiring open circuit ---heating inoperative ---HO2S Sensor
also refers to oxygen sensor (O2S) --no activity detected ===causes --- wiring---O2S
the HO2S is in the exhaust manifold before the cat converter
the O2S is after the cat converter
check the wires and connections , then replace either or both sensors

code p 0134 refers to heated oxygen sensor(HO2S) 1 bank 1--no activity detected ===causes ---wiring open circuit--heating inoperative---HO2S sensor
it also refers to oxygen sensor (O2S) 1 bank 1 --no activity===causes wiring -- oxygen sensor
HEATED oxygen sensors are in the exhaust manifold or exhaust pipe before the cat converter
oxygen sensors are in the exhaust pipe after the cat converter
bank one is the side closest to the radiator on a cross fitted engine or on the lhs with you facing the fan

Clogged catalytic converters. To check, remove the pre O2 sensor/s. If it runs better or longer, replace the cats.

Is it the front or rear sensor, it could be upto $200

There is a speed sensor that mounts in the side of the transmission.
If it fails you should have a check engine light on.

the 4 cylinder has only one oxygen sensor. this sensor is a plug in with two wires coming out of it. As the exhaust leaves the motor the o2 sensor tells the car what carbon is leaving the. The o2 sensor is located on the exhaust pipe directly leaving the motor

Your van has four o2 sensor's, the code should tell you which one is bad for exsample code should be like,
o2 sensor bank 1 sensor 1 or 2
o2 sensor bank 2 sensor 1 or 2

Also make sure you don't have a vacum leak.

Sensor 2(s) are those aft of the catalytic converter(s).
The pre-cat sensors typically fail more frequently than those post-cat.
The codes you cite are related to all sensors.
It is worth running a test of the sensors. Most garages can do the tests without any disassembly and for less than the cost of replacing any one of the four. Then you can replace the faulty unit with confidence.