O2 Oxygen Sensor Upstream Downstream for Ford Fiesta (2011-2019) 1.6L

Direct-Fit O2 Sensor Kit for 2011-2019 Ford Fiesta (B299)

What it Does: This matched upstream and downstream O2 sensor kit monitors pre- and post-catalyst exhaust oxygen on the 2011-2019 Ford Fiesta (B299) 1.6L Ti-VCT Sigma for precise closed-loop fuel control.

The Stock Ford Fiesta Oxygen Sensor Failure

Factory O2 sensors on the B299 Fiesta with the 1.6L Ti-VCT Sigma engine degrade from sustained exhaust heat cycling, carbon fouling, and moisture contamination. Over time, internal zirconia ceramic elements crack and internal heater circuits burn out, causing sluggish voltage switching. These failures skew short- and long-term PCM fuel trims and trigger P0130, P0135, P0141, or false P0420 catalyst codes.

Common Symptoms of a Failing OEM O2 Sensor

• CEL & Heater DTCs: Stored codes like P0135, P0141, P0130, or P0171 from open heaters or slow switching.
• Rough Idle & Hesitation: Skewed upstream air-fuel feedback disrupts closed-loop fueling under load.
• Failed Emissions & Low MPG: Rich fuel trims foul spark plugs and drop fuel economy.

The Direct-Fit Heated Zirconia Oxygen Sensor Solution

Replacing both sensors as a matched set restores factory response across the 1.6L Ti-VCT Sigma exhaust stream. Each unit features a laser-welded stainless housing, high-temperature zirconia ceramic element, and calibrated internal heater matching OEM specs for AE8Z9F472A, AE8Z9F472B, AE8Z9G444B, and AE8Z9G444C. Factory-style connectors and OEM-length harnesses bolt directly into stock bungs with zero wiring splicing.

What's Included

• 1 Upstream Oxygen Sensor (234-4493)
• 1 Downstream Oxygen Sensor (234-4555)

Technical Specifications

Compatibility

• 2011-2019 Ford Fiesta 1.6L (Confirm engine before ordering)

Frequently Asked Questions & Fitment Warnings

Does this fit the B299 Fiesta?

Yes. Direct fit for the 2011-2019 Ford Fiesta equipped with the 1.6L Ti-VCT Sigma engine. Confirm engine before ordering; excludes 1.6L EcoBoost ST and 1.0L EcoBoost models.

Will this clear P0135, P0141, or P0420 codes?

Yes, if sensors are faulty. New 234-4493 and 234-4555 units restore heater resistance and switching speed; inspect for exhaust leaks before clearing P0420.

Are the harnesses plug-and-play?

Yes. Factory-matched connectors and OEM lead lengths install directly into B299 exhaust bungs with zero splicing.

The Ford Precision Standard

Accurate O2 feedback keeps ECU fuel mapping sharp and emissions-compliant across daily operation. Matched upstream and downstream sensors restore CEL-free reliability on the B299 platform.