Engine shuts off of the blue

Hi,

Interestingly, a bad crankshaft position sensor can fail without setting a code. Take a look through this link:

https://www.2carpros.com/articles/symptoms-of-a-bad-crankshaft-sensor

Now the issue is this. Since it is starting right back up for you, it is going to be difficult to test.

Usually, if one is failing, they won't start working again until they cool off. During that time, you can check the sensor for an RPM signal using a live data scan tool.

If you want to try it, here are the directions specific to your vehicle.

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2017 Hyundai Elantra (AD) VIN KMH L4-2.0L
Crankshaft Position Sensor (CKPS) - Repair Procedures
Vehicle Powertrain Management Sensors and Switches - Powertrain Management Sensors and Switches - Computers and Control Systems Crankshaft Position Sensor Service and Repair Procedures Crankshaft Position Sensor (CKPS) - Repair Procedures
CRANKSHAFT POSITION SENSOR (CKPS) - REPAIR PROCEDURES
Inspection
Check signal waveform of CKPS and CMPS using a scan tool.
Specification : Refer to "Waveform"

Removal
Turn the ignition switch OFF and disconnect the battery negative (-) cable.
Disconnect the crankshaft position sensor connector (A) and remove the sensor after removing the installation bolt.

pic 1

Installation

Install the component with the specified torques.
Note that internal damage may occur when the component is dropped. If the component has been dropped, inspect before installing.

Apply the engine oil to the O-ring.
Insert the sensor in the installation hole and be careful not to damage.
Installation is reverse of removal.
Crankshaft position sensor installation bolt :
9.8 11.8 N.m (1.0 1.2 kgf.m, 7.2 8.7 lb-ft)

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Let me know if this helps or if you have other questions.

Take care,
Joe