Speed and crankshaft sensors problem. Need to find location and how to replace this parts. Check engine light is on because of this problem.

The camshaft and crankshaft sensors are located on the engine of a 2001 S10 with a 4.3L engine. The camshaft sensor is typically located on the front of the engine, near the timing cover. The crankshaft sensor is typically located on the back of the engine, near the flywheel or flexplate.
If the ECM (engine control module) fuses are blowing as soon as you turn the key on, it could indicate a problem with one or both of these sensors. The camshaft and crankshaft sensors send signals to the ECM, which uses these signals to control the engine's timing and fuel injection. If the sensors are malfunctioning or sending incorrect signals, it can cause the ECM to blow fuses.
It's important to diagnose the problem correctly and not just replace parts without properly testing them, as this can lead to wasted time and money. A proper diagnosis can be made by a mechanic with a scanner that can read the codes and check the sensors' signals.
If the problem is caused by a faulty camshaft or crankshaft sensor, it will need to be replaced. It's important to use OEM (original equipment manufacturer) parts or parts from a reputable brand, as low-quality aftermarket parts may not function correctly and could cause further problems.
It's also a good idea to check all wiring, connectors, and fuses related to the sensor, as a damaged wiring or a faulty connector can also cause the problem.
Again, it is recommended to check the vehicle's warranty status and the manufacturer's instructions to ensure that the repair or replacement will not void the warranty.

Get the codes read (most auto parts stores will do this for free), then determine what the cause may be. Sounds initially like crankshaft sensor (no rpm signal), but you would need code to verify that.

P1335 CHEVROLET P1335 CHEVROLET - Crankshaft Position Circuit Possible causes
- Faulty Crankshaft Position Sensor
- Crankshaft Position (CKP) Sensor harness is open or shorted
- Crankshaft Position (CKP) Sensor circuit poor electrical connection Help with this
Symptoms
- Engine Light ON (or Service Engine Soon Warning Light)
- Lack/Loss of Power
- Engine Stall
P1335 CHEVROLET Description
The Crankshaft Position (CKP) sensor sends pulses to the Powertrain Control Module (PCM) as the reluctor wheel teeth rotate past the CKP sensor. The PCM uses the CKP pulses to synchronize the ignition and fuel injector operation, and to time the interval between each CKP pulse. The PCM determines when an excessive change in crankshaft speed occurs by comparing each new time interval with the previous interval. A misfire causes an unexpected change in the crankshaft speed. A certain amount of acceleration/deceleration is expected between each firing stroke, but if the crankshaft speed changes more than an expected amount, the PCM interprets this as a misfire. The interval between CKP sensor pulses is extremely small. At high engine speeds, slight variations in the following components make misfire detection difficult:
- Crankshaft
- Reluctor wheel
- CKP sensor
The PCM learns variations during the Crankshaft Position System Variation Learning Procedure. The PCM compensates for these variations when performing detect misfire calculations. Only a scan tool can command the PCM to perform the Crankshaft Position System Variation Learning Procedure again.
Perform the learning procedure after the following actions:
- A PCM replacement
- Any operation or repair involving the crankshaft, the CKP sensor, or the CKP sensor to reluctor wheel gap relationship.
- An engine replacement.
- The ignition switch is in the ON position until the battery is drained.


Read more: http://nissanhelp.com/diy/obd_codes/p1335_chevrolet.html#ixzz37IoD1Imx

crankshaft position sensor location for 3.3 V6 engine is mounted at the rear of the engine on transmission bellhousing, the 3.5 V6 engine crankshaft sensor located at front of the engine on the aluminum oil pan section below crankshaft pulley.replace the crankshaft position sensor remove heat shield disconnect the electrical connector the remove sensor retaining bolt then remove crankshaft sensor.after replacing crankshaft sensor you need to erase code if check light come back on.

P0725 NISSAN - Engine Speed Signal

The P0725 Codes is triggered when TCM does not receive the engine speed signal from ECM.

The Engine Control Module (ECM) monitors the engine speed through the Crankshaft Position (CKP) sensor with the engine running, and send signal to the Transmission Control Module (TCM).

Symptoms:
- Engine Light ON (or Service Engine Soon Warning Light)

Possible causes:
- Open or shorted CKP sensor circuit condition
- Poor CKP sensor electrical connection
- Check communication error between the ECM and TCM
- Failed CKP Sensor

Possible solution:
Very common problem with Nissan vehicles, usually replacing the Crankshaft Position sensor takes care of the problem.

Keep us updated.

The check engine light doesn't have to come on with a bad crank sensor ,your vehicle has two , one for lower rpm an one for higher speeds . A&B
The two crankshaft sensors are located on the front bank (BANK 2) of the engine block between cylinders 4 and 6. Crankshaft position A sensor is located in the upper crankcase and crankshaft position B sensor is located in the lower crankcase. Both sensors extend into the crankcase and are sealed to the engine block with O-rings. The crankshaft position sensors are not adjustable.

Hi, the crank sensor is located on the drivers side rear of engine just below the starter. Very easy to replace. Once you replace the sensor and start the truck the check engine light is going to illuminate. You must preform a crankshaft variation learn. unfortunately, you need a scan tool to preform this task.
Take care

The crank sensor is located on the engine near the flywheel axis of the crankshaft.

Crankshaft Position Sensor Removal & Installation To Remove:
Location of the crankshaft position sensor on the 2.4L engine
Location of the crankshaft position sensor on the 3.0L engine
Location of the crankshaft position sensor on the 3.3L and 3.8L engines
NOTE: On the 2.4L engine, the crankshaft position sensor is mounted to the engine block behind the alternator, just above the oil filter. On the 3.0L, 3.3L and 3.8L engines, the crankshaft position sensor is mounted on the transaxle housing, above the vehicle speed sensor.

1. Disconnect the negative battery cable.
2. Raise and safely support the vehicle.
3. Disconnect the crankshaft position sensor electrical connector.
4. Unfasten the sensor mounting screw, then remove the sensor from the vehicle by pulling it straight out.

To Install:
NOTE: If the sensor removed is going to be re-installed, clean off the old spacer on the sensor face. A new spacer must be attached to the sensor face before installation. If the sensor is being replaced, be sure that a paper spacer is attached to the sensor face.

1. Install sensor and push the sensor in until contact is made. While holding the sensor in this position, install and tighten the mounting bolt to 105 in. lbs. (12 Nm).
2. Connect the crankshaft position sensor electrical connector.
3. Lower the vehicle.
4. Connect the negative battery cable.

The engine speed signal code is generated from the crank sensor. The crank sensor is located on the back side of the engine block. See image.

Thanks Jay!

A camshaft sensor can cause a no start situation, so can a bad coil, or ignition control modual. You need further testing done.
A speed sensor does not cause a no start, that I'm aware of.