Oxygen Sensors for Mazda Protege (2001-2003) 2.0L Downstream

Direct-Fit Downstream Oxygen Sensor for 2001-2003 Mazda Protegé

What it Does: The downstream oxygen sensor monitors post-catalytic exhaust gas conversion on the 2001-2003 Mazda Protegé to verify catalyst efficiency and maintain closed-loop fuel trim stability.

The Stock Mazda Protegé Secondary Sensor Degradation

Extended thermal cycling up to 1,400°F combined with unburnt hydrocarbon and silica exposure continuously fouls the factory zirconium dioxide element. On aging BJ chassis sedans, original downstream units on the FS-DE engine develop high internal resistance and slow switching frequencies. This sensor latency triggers nuisance catalytic converter diagnostic trouble codes (DTCs) such as P0420, P0136, and P0141, even when the catalyst substrate is physically intact.

The Engineering Solution

This replacement downstream sensor incorporates a precision planar ceramic sensing core shielded by a 310-grade stainless steel body to defend against exhaust contamination and thermal shock. A built-in ceramic heating element decreases light-off time, allowing the ECU to evaluate downstream oxygen levels quickly upon cold start. Built to exact factory harness lengths with OEM-spec weather-sealed pin connectors and pre-conditioned M18x1.5 rolled threads, it installs cleanly without harness splicing or signal resistance issues.

Technical Specifications

Compatibility

• 2001 Mazda Protegé 2.0L L4 (Downstream)
• 2002 Mazda Protegé 2.0L L4 (Downstream)
• 2003 Mazda Protegé 2.0L L4 (Downstream)
• 2002-2003 Mazda Protegé5 2.0L L4 (Downstream)

Frequently Asked Questions

Does this fit the BJ Protegé?
Yes, this is a direct fit for the 2001-2003 Mazda Protegé equipped with the FS-DE engine.

Will replacing a worn downstream sensor clear my P0141 and P0420 fault codes?
Yes, if the check engine light is caused by internal heater failure or slow secondary sensor response, replacing the unit and resetting the ECU clears the fault.

The Mazda Tuner Standard

Engineered to handle high-revving naturally aspirated JDM powertrains, this sensor maintains clean post-combustion diagnostics and prevents unmetered AFR drift on modified and daily-driven platforms alike.