O2 Oxygen Sensor Upstream Downstream for Kia Optima (2011-2015) 2.4L

Direct-Fit Upstream & Downstream O2 Sensor Kit for 2011-2015 Kia Optima (TF)

What it Does: Monitors exhaust air-fuel ratios on the 2011-2015 Kia Optima (TF) 2.4L GDI (G4KJ) to maintain closed-loop fuel trim and emissions compliance.

The Stock Kia Optima Sensor Failure

On the TF chassis with the Theta II 2.4L GDI (G4KJ), the factory upstream (234-5029) and downstream (234-4238) sensors endure constant exhaust heat soak and carbon soot exposure. Over time, silicate contamination or internal heater element burnout degrades the zirconia ceramic element, slowing voltage switching response. Sluggish feedback skews ECU fuel trims and triggers fault codes like P0135, P0141, or false P0420 alerts.

Common Symptoms of a Failing OEM O2 Sensor

• Check Engine Light / DTCs: Stored codes like P0133, P0135, P0141, or P0420 from slow response or heater burnout.
• Erratic Fueling: Delayed closed-loop transition causes rough idle and throttle hesitation.
• High Fuel Consumption: Over-rich mixtures lower MPG and risk catalytic converter thermal overload.

The Direct-Fit Matched O2 Sensor Solution

Replacing both sensors as a matched set restores factory closed-loop lambda control across the Theta II 2.4L GDI (G4KJ) exhaust stream. Each unit uses a corrosion-resistant stainless steel housing, laser-welded shield, and rapid-heating zirconia element calibrated to match 39210-2C210, 39210-2G100, and 39210-2G200 resistance specs. Direct-fit harnesses and OEM connectors eliminate splicing for clean signal transmission to the TF ECU.

What's Included

• 1 Upstream Oxygen Sensor (234-5029)
• 1 Downstream Oxygen Sensor (234-4238)

Technical Specifications

Compatibility

• 2011-2015 Kia Optima (TF) — 2.4L Naturally Aspirated (G4KJ)
• Excludes 2016 models, 2.0L Turbo, and other Hyundai/Kia vehicles.

Frequently Asked Questions & Fitment Warnings

Does this fit the TF Optima?

Yes. Direct fit for the 2011-2015 Kia Optima Theta II 2.4L GDI (G4KJ). Excludes 2016 models and all 2.0L Turbo engines.

Will this clear P0135, P0141, or P0420 codes?

Yes, when caused by faulty sensors. New 234-5029 and 234-4238 sensors resolve heater and response codes, though persistent P0420 requires catalytic converter inspection.

Is wiring modification needed for installation?

No. Both include OEM-style plugs for direct installation into factory bungs after clearing fault codes.

The Kia Precision Standard

Accurate lambda feedback on the TF platform protects catalytic efficiency and fuel economy, keeping your 2.4L Optima emissions-compliant and CEL-free.