39210-2M425 Car Oxygen Sensor For Hyundai Elantra Sonata Santa Fe Tucson Kona / Kia K5 Seltos Sorento

39210-2M425 Car Oxygen Sensor

Technical Notes:

• This is a 4-wire heated oxygen sensor manufactured by Hyundai Kefico Corporation (OEM supplier)

• The heating element allows the sensor to reach operating temperature quickly, enabling the ECU to enter closed-loop fuel control sooner

• The sensor measures oxygen concentration in exhaust gases and sends voltage signals to the ECU for air-fuel ratio optimization

• For zirconium-type sensors, output voltage is approximately 0.6 - 1.0 V under rich conditions, and near 0 V under lean conditions

This Lambda Sensor replaces the following Original Equipment Manufacturer (OEM) and interchange part numbers. Check your old sensor to confirm a match:

Important Notes on Cross-Reference:

• This sensor is the downstream / rear oxygen sensor counterpart to the front sensor (39210-2M412) on many Hyundai/Kia vehicles

• Aftermarket sensors may use different interchange numbers — always verify connector shape and wire length before purchasing

This Lambda Sensor is primarily used in Hyundai and Kia vehicles equipped with 1.6L turbocharged petrol engines. It functions as the downstream (post-catalyst / rear) oxygen sensor.

Additional Compatibility:

• Kauai / Kona (2020-2023)

• Hyundai Avante

• Sonata DN8 (2019-2023)

Fitment Notes:

• This is a downstream (post-catalyst / rear) sensor — NOT for upstream/pre-catalyst positions

• Compatible with 1.6L Turbo and 1.6L Turbo Hybrid petrol engines

• Confirmed applications include vehicles built on Hyundai-Kia platforms with G4FS (1.6L Turbo) engine

• When replacing, verify your vehicle has a 4-pin heated O2 sensor in the downstream position

Consider replacing your Lambda Sensor if you experience any of the following:

Check Engine Light (MIL) Illumination

• Illuminated check engine light (often the first and only obvious symptom)

• Common OBD-II fault codes for this sensor include:

  • P0136 — O2 Sensor Circuit Malfunction (Bank 1, Sensor 2)

  • P0137 — O2 Sensor Circuit Low Voltage (open circuit)

  • P0138 — O2 Sensor Circuit High Voltage (short circuit)

  • P0036 — HO2S Heater Control Circuit (Bank 1, Sensor 2)

  • P0141 — O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 2)

  • P0420 — Catalyst System Efficiency Below Threshold (Bank 1) — often caused by a failing downstream O2 sensor

Performance & Driveability Issues

• Increased fuel consumption — The ECU may default to rich mixture parameters, wasting fuel⛽

• Poor engine performance / hesitation — Engine struggles during acceleration

• Rough idle or stalling — Unstable engine operation at low speeds

• Reduced engine power — Noticeable loss of performance, especially under load

Exhaust & Emissions Symptoms

• Failed emissions / smog test — The catalyst monitor cannot complete without proper sensor feedback

• Readiness monitors won’t set — The O2 sensor and catalyst monitors remain "Not Ready," blocking inspection passes

• Increased exhaust emissions — Incorrect air-fuel ratio leads to higher pollutant output

Potential causes of sensor failure:

• Normal wear and tear — Over time (typically 60,000 - 100,000 miles), the sensor element degrades

• Heater circuit failure — The internal heating element stops functioning, causing slow response

• Contamination — Oil, coolant, or silicone sealants can damage the sensing element

• Exhaust leaks — Upstream leaks can introduce false oxygen readings

• Wiring / connector issues — Damaged wiring or loose connector contacts

Diagnostic Tip:

• A faulty downstream O2 sensor often triggers codes like P0136, P0137, or P0138. While the engine may still run, fuel economy is negatively affected

• If you experience a flashing check engine light, address the issue immediately to prevent catalytic converter and O2 sensor damage

• The P0036 code specifically indicates a heater control circuit problem, not an air-fuel ratio reading problem

1. Confirm Position — This is a DOWNSTREAM Sensor

• This part number (39210-2M425) is the downstream (post-catalyst / rear) oxygen sensor

• Do not confuse with the upstream sensor (39210-2M412) — they are NOT interchangeable

• Verify the location of your old sensor before ordering

• Check whether your vehicle has Bank 1, Sensor 1 (upstream) or Bank 1, Sensor 2 (downstream)

2. Engine & Vehicle Verification

• This sensor is compatible with 1.6L Turbo and 1.6L Turbo Hybrid petrol engines

• Common engine code: G4FS (Hyundai/Kia 1.6L Turbo)

• Not compatible with 2.0L Turbo, 2.4L, 2.5L, or diesel engines (use different part numbers)

• Always verify your specific model year and engine code before ordering

3. Connector & Physical Fitment Verification

• This sensor features a 4-pin connector

• Wire length is approximately 405 mm

• Always visually inspect your old sensor's connector shape and wire length before ordering

• Important: Aftermarket sensors may have different connector designs — confirm match before purchase

4. Genuine OE vs. Aftermarket Quality

• The OEM manufacturer for this part is Hyundai Kefico Corporation

• Genuine OE sensors are precision-designed to meet the exact specifications of your vehicle's ECU

• Aftermarket sensors may have different calibration parameters, leading to:

  • Premature failure

  • Inaccurate readings

  • Persistent check engine light codes

• For optimal plug-and-play fitment and reliable performance, OE-spec sensors are strongly recommended

5. Replacement Interval

• Lambda sensors degrade over time, often without triggering immediate fault codes

• Replacement every 60,000 - 100,000 miles (100,000 - 160,000 km) is recommended to maintain:

  • Optimal fuel efficiency

  • Catalytic converter health and longevity

  • Proper emissions output

  • Smooth engine operation

6. Installation Tips

• Allow exhaust system to cool completely before removal to avoid burns and prevent thread damage

• Use an O2 sensor socket (22mm / 7/8") to prevent stripping

• Apply anti-seize compound to the threads (avoiding the sensor tip) to prevent seizing in the exhaust bung

• Do not use silicone sealants near the exhaust system — contamination will destroy the sensor

• Avoid touching the sensor tip — skin oils can contaminate the sensing element

• Do not drop the sensor — the ceramic element can crack upon impact

• Tighten to manufacturer specification — Approximately 45 N·m (4.5 kg·m, 32.5 lb-ft)

• Secure wiring harness with proper clips to prevent contact with hot exhaust components or moving parts

• After installation, start the engine and check that no exhaust gas leakage exists

7. Required Tools

• O2 sensor socket (22mm / 7/8") or deep offset wrench

• Ratchet and extension bar (for access)

• Anti-seize compound (sensor-safe, if not pre-applied)

• Jack and jack stands (if under-vehicle access requires lifting)

• OBD-II scanner (to clear fault codes and verify operation after replacement)

8. Quantity Needed

• Most 4-cylinder vehicles require two sensors: one upstream (pre-cat) and one downstream (post-cat)

• This part (39210-2M425) is the downstream sensor

• If both sensors are faulty, you will need to purchase the appropriate part numbers for each position

9. Warranty

• Genuine Hyundai/Kia OE parts typically include a manufacturer warranty

• Aftermarket sensors may offer varying warranty periods (typically 1-2 years)

• Check with your specific retailer for their warranty terms and return policy

• Important: Most warranties are voided if the sensor tip shows contamination from improper handling (e.g., touching the tip, dropping, or silicone exposure)

10. Professional Installation Recommended

• While this is a direct-fit part, professional installation is recommended if you are not experienced with automotive exhaust systems

• Improper installation can lead to:

  • Exhaust leaks around the sensor bung

  • Cross-threaded or damaged exhaust threads

  • Sensor damage from contamination or mishandling

  • Wiring damage from contact with hot exhaust components

• After replacement, the ECU may need to have adaption values reset using diagnostic equipment

Disclaimer: While we strive for accuracy, vehicle specifications and OE part numbers may vary by production date, market region, and vehicle trim level. This part number (39210-2M425) is a Hyundai/Kia OE number for downstream (post-catalyst) applications on 1.6L turbocharged petrol engines. Always verify physical fitment (connector shape, wire length, and thread size) and confirm the position (upstream/downstream) of your old sensor before purchasing. For non-Hyundai/Kia applications, confirm compatibility with your vehicle's manufacturer specifications.