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2020 Outlander SEL - P0420 Code and Check Engine Light On

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Tom H. · rep 0 · May 22, 5:31 AM · 1 replies · solved · Question

Vehicle: 2020 Mitsubishi Outlander SEL

Hey everyone,

My 2020 Mitsubishi Outlander SEL just threw a Check Engine Light this morning. I used my OBD-II scanner and it's showing a P0420 code: 'Catalyst System Efficiency Below Threshold (Bank 1)'.

The car seems to be driving fine, no noticeable loss of power or strange noises, but the light is definitely on. I've heard this can be a few different things, from a bad O2 sensor to something more serious like the catalytic converter itself.

Has anyone else experienced this with their Outlander, especially a 2020 model or similar? What was the fix for you? I'm trying to figure out if this is something I can look into myself or if it's an immediate trip to the dealership.

Any advice or shared experiences would be greatly appreciated!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 5:31 AM

0

ClearTheCode admin answer:

The P0420 code on your 2020 Mitsubishi Outlander SEL indicates that the catalytic converter system for Bank 1 is not operating at peak efficiency. While the car might seem to drive normally, it's important to address this to ensure proper emissions control and prevent potential damage.

Here's a breakdown of common causes and steps:

  1. Oxygen Sensors (O2 Sensors): Often, a faulty upstream or downstream O2 sensor can trigger a P0420. The downstream sensor, in particular, monitors the catalytic converter's efficiency. If it's reading incorrectly, it can falsely report an issue with the converter.
  2. Exhaust Leaks: Leaks in the exhaust system before or near the catalytic converter can allow unmetered air in, affecting O2 sensor readings and leading to a P0420 code.
  3. Catalytic Converter Failure: Over time, catalytic converters can degrade or become clogged, losing their ability to efficiently convert harmful exhaust gases. This is a more expensive repair but is a direct cause of the P0420 code.
  4. Engine Misfires or Rich/Lean Conditions: Persistent engine problems that lead to unburnt fuel entering the exhaust system can damage the catalytic converter over time.

When to see a shop:

  • Persistent Code: If the code returns after clearing, or if you notice any changes in engine performance (e.g., reduced power, poor fuel economy, rough idle), it's time to visit a qualified mechanic.
  • Diagnostic Tools: A professional shop has advanced diagnostic tools to monitor O2 sensor live data and perform back-pressure tests on the catalytic converter, which can accurately pinpoint the root cause.
  • Emissions Testing: If your state requires emissions testing, this code will cause your vehicle to fail.

While an O2 sensor replacement might be a DIY task for some, diagnosing the exact cause of a P0420 can be complex. Given that your vehicle is a 2020 model, it's worth having a professional diagnose it to ensure the correct component is replaced and to prevent further issues.

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