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2018 Charger R/T - P0420 Code and sluggish acceleration

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Jason D. · rep 0 · May 22, 5:37 AM · 1 replies · solved · Question

Vehicle: 2018 Dodge Charger R/T

Hey everyone,

My 2018 Dodge Charger R/T, with about 75,000 miles, just threw a Check Engine Light. I scanned it with my OBD-II reader, and it's showing a P0420 code: "Catalyst System Efficiency Below Threshold (Bank 1)".

Lately, I've also noticed the car feels a bit sluggish, especially when accelerating from a stop or trying to pass on the highway. It's not a huge difference, but definitely noticeable compared to how it used to feel. Fuel economy also seems to have dipped slightly.

Could this P0420 code be directly related to the performance issues? What's the typical fix for this, and is it something I can troubleshoot myself before taking it to a shop? Any advice would be greatly appreciated!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 5:37 AM

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ClearTheCode admin answer:

The P0420 code on your 2018 Dodge Charger R/T indicates that the catalytic converter on Bank 1 is not operating at optimal efficiency. This is a common issue and can definitely contribute to the sluggish acceleration and reduced fuel economy you're experiencing.

Here's a breakdown of potential causes and steps:

  1. Catalytic Converter Failure: This is the most direct cause. Over time, catalytic converters can become clogged or fail internally, reducing their ability to convert harmful emissions. This is often a result of other underlying engine issues.
  2. Oxygen Sensor Issues: While the code points to the catalyst, faulty upstream or downstream oxygen sensors can sometimes provide inaccurate readings, leading the PCM to incorrectly believe the converter is inefficient. A failing O2 sensor can also affect fuel trim.
  3. Exhaust Leaks: Leaks in the exhaust system before or near the catalytic converter can allow unmetered air in, affecting O2 sensor readings and triggering the P0420 code.
  4. Engine Misfires or Rich/Lean Conditions: Persistent misfires, excessive oil consumption, or an engine running too rich or too lean can damage the catalytic converter over time by introducing unburnt fuel or contaminants into the exhaust.

When to see a shop:

  • Initial Diagnosis: While you've pulled the code, a professional diagnosis is crucial. A shop can perform advanced diagnostics, including live data monitoring of O2 sensor readings, backpressure tests, and visual inspections of the exhaust system.
  • Complex Repairs: Replacing a catalytic converter is a significant repair, often requiring specialized tools and knowledge. If the issue is an O2 sensor, it might be more manageable, but proper torque and anti-seize application are important.
  • Underlying Issues: It's vital to identify and fix any underlying engine problems (like misfires or oil burning) before replacing the catalytic converter, otherwise, the new converter could be damaged again quickly. A shop can accurately diagnose these root causes.
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