O2 Oxygen Sensor 1 Upstream Rear For Mitsubishi Endeavor Lancer (2004-2011)

Restore your Mitsubishi’s fuel economy and eliminate that stubborn Check Engine Light with a sensor designed to survive the high-heat cycles of the 4G94 and 6G75 platforms.

Replacement Upstream or Downstream Oxygen Sensor for Mitsubishi Lancer, Montero, and Endeavor

If you've noticed a sudden drop in MPGs or a sluggish throttle response in your Lancer or Montero, your factory O2 sensors are likely "lazy" or completely fouled. On these Mitsubishi platforms, the ECU relies heavily on the voltage swing from the oxygen sensors to manage the air-fuel ratio. When the internal heater circuit fails or the zirconia element becomes coated in carbon, the car defaults to a "rich" map, wasting fuel and eventually clogging your expensive catalytic converters.

This replacement sensor is engineered to mirror the factory output signal, ensuring your fuel trims stay within the tight tolerances required by Mitsubishi's electronics. Whether you are dealing with the 2.0L L4 in a Lancer or the torque-heavy 3.8L V6 in the Endeavor and Montero, this sensor provides the precision needed for a smooth idle and peak combustion efficiency. We know that reaching the upstream location behind the block or the downstream spot near the tailpipe can be a knuckle-busting job—which is why this unit features a direct-fit harness to save you time and frustration.

Built with a 4-wire configuration and a 750mm lead, this sensor provides the reach necessary for both front and rear bank applications as specified. The black connector is keyed specifically for the Mitsubishi harness, meaning you won't have to deal with the "universal" sensor headache of cutting, crimping, or heat-shrinking wires under the chassis.

Why You Need This Upgrade

• Direct-Fit Harness: Features the correct black factory-style connector for a true "plug-and-play" installation without splicing.
• Precision Fuel Management: Restores accurate air-fuel ratio data to the ECU to improve throttle response and fuel mileage.
• Durable 4-Wire Heater: Designed to reach operating temperature quickly, reducing cold-start emissions and "Open Loop" run time.
• OEM-Spec Lead Length: The 750mm wire ensures plenty of slack for safe routing away from hot exhaust manifolds.
• Strict QC Testing: Every sensor is bench-tested to ensure the voltage output matches the 0-1V swing required for Mitsubishi diagnostics.

Installation Notes

For the 3.8L V6 models, ensure you identify whether your fault code (CEL) refers to Bank 1 or Bank 2. We highly recommend using a dedicated O2 sensor socket and applying a small amount of high-temp anti-seize to the threads (avoiding the sensor tip) to prevent future galling in the exhaust bung. If your vehicle is high-mileage, spray the old sensor with a penetrating catalyst 24 hours before the job to make removal easier.

Replaces These OEM Applications & Part Numbers

• 2003-2006 Mitsubishi Lancer 2.0L L4
• 2000-2006 Mitsubishi Montero 3.8L V6
• 2005-2011 Mitsubishi Endeavor 3.8L V6

234-4741

Clear your codes and get your Mitsubishi back to its factory-smooth performance with a sensor that actually speaks the right language.