If it is locked, it will need to be replaced. Since the belt may be too tight to get off, you may need to cut it off.
Here are directions for replacing the tensioner. The attached pic correlates with the directions.
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2017 Hyundai Elantra (AD) VIN KMH L4-2.0L
Drive Belt Tensioner - Repair Procedures
Vehicle Engine, Cooling and Exhaust Engine Drive Belts, Mounts, Brackets and Accessories Drive Belt Tensioner Service and Repair Procedures Drive Belt Tensioner - Repair Procedures
DRIVE BELT TENSIONER - REPAIR PROCEDURES
Removal and Installation
Disconnect the drive belt.
(You may need to cut your belt off)
Remove the drive belt tensioner (A).
Tightening torque :
center bolt :
29.4 - 41.2 N.M (3.0 - 4.2 kgf.M, 21.7 - 30.4 lb-ft)
fxing bolt :
39.2 - 49.0 N.M (4.0 - 5.0 kgf.M, 28.9 - 36.2 lb-ft)
pic 1
Install in the reverse order of removal.
Let me know if this helps or if you have questions.
Joe
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Tuesday, January 26th, 2021 AT 3:13 PM