2021 Hyundai Elantra Engine Stall Service Campaign

Important Warnings and Notices

Hyundai has issued several important directives regarding Service Campaign T6B (bulletin 21-01-017H):

• Dealer Stock and Retail Vehicles: Dealers are mandated to perform this Service Campaign on all affected vehicles before customer retail delivery. The update must also be performed whenever an affected vehicle is brought in for any maintenance or repair.
• During Software Update: Technicians must ensure that no cables connected to the vehicle or scan tool are disconnected during the update. The engine must not be started, and the ignition switch must not be turned off while the update is in progress.
• Low Battery Voltage: A "Warning! lower Battery Voltage. BATTERY VOLTAGE: 11.7" message may appear if the vehicle battery is below 12 volts. If this occurs, a fully charged battery jump pack or GR8 charger should be connected in "Power Supply Mode" to continue the software update, or the battery should be charged for 20 minutes with the engine idling and headlights on before retrying the update.
• Manual Update: The manual update procedure should only be attempted if the automatic update procedure is unsuccessful.

Symptoms

Owners of affected 2021 Hyundai Elantra vehicles may experience a potential Hyundai Elantra engine stall condition. This stall typically occurs immediately after the Forward Collision Avoidance (FCA) system activates, specifically under conditions of low engine RPM and low vehicle speeds. If a low-speed stall does happen, the engine can be immediately restarted.

Diagnosis / Trigger Conditions

The root cause of the Hyundai Elantra engine stall is identified as an issue within the Intelligent Variable Transmission (IVT) damper clutch logic. This logic flaw becomes apparent when the Forward Collision Avoidance (FCA) system engages while the vehicle is operating at low engine RPM and low vehicle speeds.

Repair Procedure Summary

The repair involves updating the Transmission Control Unit (TCU) software to revise the damper clutch logic. This procedure is performed by an authorized Hyundai dealer using the GDS-M diagnostic tool.

Automatic Update Procedure:

1. The GDS-M software update is performed, referencing TSB 15-GI-001 for detailed instructions.
2. The TCU adaptive learning values are reset.
3. The engine is started to confirm proper vehicle operation.

Manual Update Procedure (if automatic fails):

1. If the automatic update is unsuccessful, the ignition is turned off for approximately 10 seconds, then turned back on. The control unit is reset.
2. From the GDS-M home screen, the technician selects "ECU Upgrade."
3. On the "ECU Upgrade" screen, "Manual Mode" is selected, followed by "Update Event 677."
4. A password prompt appears; the technician enters "3917" and selects "Upgrade."
5. Once the update completes, the ignition is turned off for 10 seconds, then turned back on.
6. Any Diagnostic Trouble Codes (DTCs) that may have been created by the update are checked and cleared.
7. The TCU adaptive learning values are reset.
8. The engine is started to confirm proper vehicle operation, completing the service procedure.

Required Tools or Parts

To perform this update, technicians require the GDS-M diagnostic tool. In cases of low battery voltage, a fully charged battery jump pack or GR8 charger may be necessary. The software update targets specific Transmission Control Unit (TCU) Part Numbers (PCU P/No.) and ROM IDs. Affected PCU Part Numbers include: 39171-2JCB5, 39173-2JCB0, 39171-2JCC0, 39171-2JCC5, 39173-2JCC0, 39171-2JBD5, 39171-2JBE0, 39171-2JBB5, and 39171-2JBC0. The update typically involves replacing older ROM IDs such as CCN0N20NS0, CCN0N20NS1, and CCN0N20NS2 with the new ROM ID CCN0N20NS5.

Owner Action

If you own a 2021 Hyundai Elantra (CN7/CN7a) and are concerned about the potential for a Hyundai Elantra engine stall, you should contact your authorized Hyundai dealer. This is a Service Campaign (T6B), meaning the necessary Transmission Control Unit (TCU) software update will be performed free of charge. Dealers are instructed to perform this update on all affected vehicles, whether they are new vehicles awaiting retail delivery or existing vehicles brought in for service.

NHTSA ID: 10189981