This 4-wire narrow-band oxygen sensor fits 2005-2018 Smart Forfour with the 0.9L I3, 1.0L I3 or 1.5L I4 engines and signals whether the exhaust is running rich or lean so the engine computer can trim fuel delivery. A built-in heater brings the element to operating temperature quickly after a cold start.

Walker Products 350-34955 Oxygen Sensor Features:

• Fits 2005-2018 Smart Forfour with the 0.9L I3, 1.0L I3, 1.5L I4 engines
• Used in both upstream and downstream positions, depending on application
• 4-wire narrow-band oxygen sensor
• Built-in heater for fast warm-up
• M18x1.5 threaded mounting with a 22 mm hex
• Male rectangle connector at the harness end with 4 spade terminals
• Platinum electrode layer with a protective coating against combustion residue