Check engine light, crankshaft - 2004 Hyundai Elantra

https://www.youtube.com/watch?v=CkPEtBmFKBk
The Most Common Failure Crankshaft Position Sensor Symptoms

1. Check Engine Light Is On. Check engine light comes on if the sensor is overheated. ...
2. Vibrations in the Engine. Vibration from engine is usually the cause. ...
3. Slow Response from the Accelerator. ...
4. Erratic Starting. ...
5. Misfiring of the Cylinder. ...
6. Stalling and Backfiring.

https://carfromjapan.com/article/car-maintenance/common-crankshaft-position-sensor-symptoms/

What engine ? 2.9 - 3.7 - 4.8 - 5.3 L An do you mean- crankshaft position (CKP) sensor ? My GM service info shows only one on each of these engines ! What kind of problem are you having ? A no start - no spark ?

Possible causes
- Faulty Crankshaft Position (CKP) Sensor
- Crankshaft Position (CKP) Sensor harness is open or shorted
- Crankshaft Position (CKP) Sensor circuit poor electrical connection
- Communication error between the Engine Control Module (ECM) and Transmission Control Module (TCM)

The P0727 Codes is triggered when the TCM receives no signal from the ECM.
Possible symptoms
- Engine Light ON (or Service Engine Soon Warning Light)
P0727 Description
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).

P0336 Honda - Crankshaft Position Sensor 'A' Circuit Range/Performance

Possible causes
- Faulty crankshaft position sensor
- Crankshaft position sensor harness is open or shorted
- Crankshaft position sensor circuit poor electrical connection
- Signal plate may be damage
- Starter motor may be faulty
- Starting system circuit
- Dead or weak battery

possible that the sensor is loose and hitting on the rotor
check for loose / worn timing chains and hydraulic adjusters

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.

P1345 is "Crankshaft position sensor / Camshaft position sensor correlation"

Code P1345 determines if the distributor is installed incorrectly, or if a mechanical malfunction is present in the engine. The light will trigger when the engine is running and the camshaft sensor reference pulse is not detected at a correct relative position with the crankshaft pulse. Most likely causes for this Chevy check engine light code include a faulty crankshaft position sensor, a wiring concern or an improperly installed distributor. A quick check on the crankshaft sensor is to monitor the RPM value with a scan tool while revving up the engine. If the reading is close to twice the expected RPM, then the sensor is likely faulty. There are other less likely concerns possible, such as base engine or computer related issues, but these involve more in depth testing. I hope this information is useful.

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.

The cam sensor is out of correlation with the crankshaft. Check both the crankshaft sensor and the camshaft sensor on vehicle. Also check the wiring to each sensor for broken or damage wires. Hope this will help you.

Code 12 means That the Crankshaft position sensor may need replacement.It is located near the crankshaft maybe under the timing cover.