2024-2025 Hyundai Elantra Check Engine Light TSB

Owners of 2024-2025 Hyundai Elantra vehicles equipped with the 2.0L AKS NU PE engine may experience an illuminated Hyundai Elantra Check Engine light. This warning light is typically accompanied by specific diagnostic trouble codes (DTCs) related to the vehicle's Integrated Thermal Management Module (ITM) and Oxygen Sensor monitoring system.

Symptoms

The primary symptom is an illuminated Hyundai Elantra Check Engine light on the dashboard. This indicates that the Engine Control Module (ECM) has detected a fault within the engine or emissions system. The underlying issues are related to the vehicle's cooling system performance and oxygen sensor response.

Fault codes / DTCs

Technicians may find one or both of the following diagnostic trouble codes (DTCs) stored in the vehicle's ECM:

| Code | Description | Module | | :--- | :--- | | P218100 | Cooling System Performance | Engine Control Module (ECM) | | P013300 | O2 Sensor Circuit Slow Response (Bank 1 / Sensor 1) | Engine Control Module (ECM) |

Diagnosis / trigger conditions

The illuminated Check Engine light and associated DTCs P218100 or P013300 are triggered when the ECM detects irregularities in the Integrated Thermal Management Module (ITM) logic or the Oxygen Sensor's monitoring. These conditions indicate that the engine's thermal management or exhaust gas sensing is not operating within specified parameters.

Repair procedure summary

The repair involves updating the Engine Control Module (ECM) software to improve the logic for the Integrated Thermal Management Module (ITM) and Oxygen Sensor monitoring. This software update is performed using a Hyundai-specific scan tool (GDS-Smart).

1. Ensure the vehicle's battery charge is above 11.0 Volts and the scan tool's battery charge is above 30% to prevent update failure.
2. Turn off all lamps and accessories, and ensure the ignition switch is in the ON position.
3. Perform the ECU update in Auto Mode using the GDS-Smart tool. For detailed instructions on using the GDS-Smart, refer to TSB # 25-GI-011H.
4. Verify the current ROM ID of the vehicle's Engine system against the ROM ID Information table provided in the bulletin before proceeding with the update.
5. After the update is 100% complete, cycle the ignition OFF for at least 10 seconds (or up to 30 seconds for some models) to reset the control unit.
6. Take a screenshot of the ECU Update "Success" screen and upload it for digital documentation. The VIN/Date/Time/Mileage photo imprint is not required for GDS screenshots.
7. Perform an All Systems Fault Code search and clear any incidental DTC history that may have occurred during the update process.
8. Remove the power connector from the in-cabin fuse box for at least 5 seconds, then reconnect it. Alternatively, disconnect the negative (-) 12V battery terminal for at least 5 seconds, then reconnect it.
9. Start the engine to confirm proper operation.

Required tools or parts

Technicians will need specific tools and software to perform this update:

• Diagnostic Tools:
  • VCI 3 (Tool Number: GOVHNNN06)
  • VCI 2 (Tool Number: G1XDDMN001) - Note: VCI 2 can no longer be ordered but can be used for updates in this TSB.
• Software Update Event: Event Number 1277 (CN7 PE ECU UPGRADE FOR EARLY INTERVENTION OF ITM ISSUES).
• ECU Part Numbers and ROM IDs: The bulletin lists specific ECU Part Numbers and associated Current and Latest ROM IDs for 2024MY and 2025MY Elantra models, including:
  • 39100-2J340 (CNEVD0AMF3XCSPGA to CNEVD0AMF3XCFPGB)
  • 39100-2J341 (CNEVD0AMFCXCSPGA to CNEVD0AMFCXCFPGB)
  • 39100-2J342 (CNEVD0ANF3XCSPGA to CNEVD0ANF3XCFPGB)
  • 391X2-2J355 (CNGVD0AMFCXCSPJA, CNGVD0AMFCXCSPJB to CNGVD0AMFCXCSPJC)
  • 391X2-2J356 (CNGVD0ANF3XCSPJA, CNGVD0ANF3XCSPJB to CNGVD0ANF3XCSPJC)

Important warnings

Owners and technicians should be aware of critical instructions during the update process:

• Do NOT leave the headlamp switch in auto mode during the update.
• Do NOT disconnect any cables connected to the vehicle or scan tool during the update.
• Do NOT start the engine OR place the vehicle in Ready mode during the update.
• Do NOT turn OFF the ignition switch during the update.
• VCI 2 diagnostic tools can NO longer be ordered, but existing units can still be used for this TSB.

Owner action

If your 2024-2025 Hyundai Elantra is displaying a Check Engine light and you suspect it's related to DTC P218100 or P013300, you should visit an authorized Hyundai dealership. The ECU software update described in TSB 26-EM-006H is a warranty repair, meaning it should be performed at no cost to the owner. The dealership will diagnose the issue and apply the necessary software update to resolve the Hyundai Elantra Check Engine light concern.

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Source: NHTSA ID 11029942