P0605 on 2021 Kia Seltos: Understanding the ECM ROM Error and TSB Fix

What's Unique About the 2021-2021 Kia SELTOS

What makes the 2021 Seltos unique regarding P0605 is that Kia has officially acknowledged the problem and issued a Technical Service Bulletin (TSB ENG227, also known as Service Action SA463). This isn't a random hardware failure but a specific, documented software bug affecting both the Seltos and the 2020-2021 Kia Soul with the same 2.0L Nu engine. This removes most of the diagnostic guesswork, as the solution is a known ECM software update rather than a costly and speculative hardware replacement.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Symptoms You May Notice

• Check Engine Light (MIL) is on
🎬 Watch: A quick guide to understanding the P0605 engine code
• Engine may stall or hesitate
• Hard starting or no-start condition
• Engine misfires or runs rough
• Illuminated ABS or traction control light
• Transmission may not shift properly

Most Likely Causes

1. Outdated ECM Software Logic 🔴 High Probability Kia issued Technical Service Bulletins (TSB_ENG227_R1 and TSB_ENG227_R2) specifically to address DTC P0605 on 2021 Seltos models with the 2.0L Nu engine produced from November 20, 2019 through January 8, 2021.
   How to confirm: A Kia dealer can check the vehicle's VIN and current software version (ROM ID) against the affected list for Service Action SA463. The TSB provides a table of old and new ROM IDs to verify if the update has been performed.
   Typical fix: Reflashing the ECM with the improved software provided by Kia. This is performed by a dealer using a KDS diagnostic tool and is often covered under warranty or as a no-charge service action.
   Est. part cost: $0

Rare But Worth Checking

• Failing Engine Control Module (ECM): → Shop Engine Control Module (ECM) While the TSB points to software, a genuine hardware failure of the ECM is still possible, though much less likely. This should only be considered after the software update has been performed and the code returns. A replacement ECM must be programmed to the vehicle's VIN.
• Low Battery Voltage or Poor Grounds: → Shop Vehicle Battery Low voltage during startup can sometimes trigger spurious internal module errors. It's always wise to ensure the battery and charging system are healthy before proceeding with more complex diagnostics. The TSB for the reflash even recommends connecting a battery charger during the procedure to ensure stable voltage.
• Underlying Engine Mechanical Issues (Misdiagnosis): It is critical to be aware of Kia recall SC209 for the 2021 Seltos 2.0L engine, which addresses improperly heat-treated piston oil rings. 🎬 See why some Kia engines stall even after recent service The symptoms, including stalling and rough running, can mimic an ECM failure. A dealer should verify the status of all recalls before diagnosing P0605.

Diagnosis Steps

1. Verify that code P0605 is active using an OBD-II scanner.
2. Check if code P2181 is also present, as it is commonly associated with the same issue per the TSB.
3. Contact a Kia dealership with your vehicle's VIN.
4. Inquire about 'Service Action SA463' or 'TSB ENG227' to see if your vehicle is eligible for the free ECM software update. Also, ask about the status of engine recall 'SC209'.
5. If the service action is open, schedule an appointment to have the ECM reflashed. This is the most probable solution and is often done at no charge.
6. If the TSB does not apply or has already been performed, test the battery and charging system to rule out any voltage-related issues. The alternator should provide 13.0 to 14.5 volts with the engine running.
7. If the code persists after the update and voltage checks, a deeper diagnosis of the ECM and its wiring by a qualified technician is required. ECM replacement, which requires VIN programming, should be the final step.

Parts You'll Likely Need

• Engine Control Module (ECM) Software Update — This is not a physical part, but the service required to fix the known software glitch as per Kia's TSB SA463.
  OEM price range: $0 - $200
  Aftermarket price range: N/A
• Engine Control Module (ECM) (OEM #39171-2EPV0 (AWD), 39171-2EPT0 (FWD)) — This is only needed in the rare case that the ECM has a hardware failure that persists after the software update is performed. Part number varies by drivetrain (AWD vs FWD). Always verify with VIN.
  Trusted brands: Kia (OEM)
  OEM price range: $800-$1200
  Aftermarket price range: $400-$700

Related Codes That Often Appear With This One

• P2181 — The Kia TSB (SA463) explicitly states that the same ECM logic improvement addresses both P0605 (Internal Control Module Read Only Memory (ROM) Error) and P2181 (Cooling System Performance), indicating the software flaw can trigger either or both codes.

Technical Service Bulletins (TSBs) & Recalls

• TSB_ENG227_R2: SERVICE ACTION: MIL ON DTC P0605 AND/OR P2181 ECM LOGIC IMPROVEMENT (SA463)
• TSB_ENG227_R1: SERVICE ACTION: MIL ON DTC P0605 AND/OR P2181 ECM LOGIC IMPROVEMENT (SA463)

Platform-Specific Known Issues

• The 2021 Kia Seltos with the 2.0L Nu MPI engine is subject to Kia Service Action SA463 (detailed in TSBs ENG227_R1 and ENG227_R2). This action was created to correct a software logic flaw in the ECM that causes DTC P0605 and/or P2181 to be stored. The official repair is a software update, not hardware replacement.
• Affected vehicles were produced between November 20, 2019, and January 8, 2021.
• This issue is shared with the 2020-2021 Kia Soul, which uses the same engine and was included in the same service action.

Mechanic-Grade Diagnostic Values

• Alternator Output Voltage — expected: 13.0 to 14.5 Volts with the engine running.. Failure: Voltage below 13.0V or significantly above 14.5V indicates a charging system problem that could trigger spurious module errors.
• Battery Voltage (Engine Off) — expected: Approximately 12.6 Volts.. Failure: Voltage significantly below 12.4V indicates a weak or discharged battery that can cause module initialization errors upon startup.

Scan Tool Commands That Help

• Kia Diagnostic System (KDS): ECU Upgrade — This is the primary function used to reflash the ECM with the updated software logic to resolve P0605 as per TSB SA463. The specific event is #520 for the Seltos (SP2).
• Kia Diagnostic System (KDS): Coolant Discharging Mode of Electric Thermostat — This procedure must be performed before the ECU Upgrade if DTC P2181 is also present. It is a preparatory step required by TSB SA463.
• Kia Diagnostic System (GDS/KDS): Resetting Adaptive Values — This function is used to reset the ECM's learned values after a major repair or replacement. While not explicitly for P0605, it is a common step after module-related work to ensure the system relearns correctly.
• Kia Diagnostic System (GDS/KDS): VIN Writing — This is a mandatory step when replacing the ECM. The new module must be programmed with the vehicle's VIN to function and communicate with the immobilizer system.

Wiring & Ground Locations

• OBD-II Connector — Under the driver's side of the instrument panel.. This is the connection point for the Kia Diagnostic System (KDS) tool required to perform the TSB software update.
• ECM Location (General) — Typically found in the engine bay, often mounted to the firewall or near the battery/fuse box.. Physical inspection of the ECM and its connectors for corrosion, water intrusion, or physical damage is a valid diagnostic step if the software update fails to resolve the code.

OEM Part Supersession History

• 39172-2EPV0 → 39173-2EPV0 — Part number update or revision by the manufacturer. The function remains the same.

Model Year Variations Within This Range

• 2021: TSB SA463 specifies different software 'Event' numbers based on the production date. Seltos (SP2) models produced from Nov 20, 2019, to Oct 15, 2020, use Event #520. Models from Oct 16, 2020, to Jan 13, 2021, use Event #619. This is critical for the technician performing the update.