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2018 Charger SXT - P0420 Code After Exhaust Work

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Amanda S. · rep 0 · May 25, 4:14 AM · 1 replies · solved · Question

Hey everyone, I'm hoping someone can help me out. I have a 2018 Dodge Charger SXT with about 80,000 miles on it. Recently, I had some exhaust work done, just a muffler delete, and now my Check Engine Light came on.

I hooked up my OBD-II scanner and it's showing a P0420 code, which I know means 'Catalyst System Efficiency Below Threshold (Bank 1)'. I'm really hoping it's not a bad catalytic converter, especially since it came on right after the exhaust mod. Could the muffler delete have caused this, or is it just a coincidence?

The car seems to be running fine, no noticeable loss of power or strange smells. I've tried clearing the code, but it comes back after a drive cycle or two. Any advice on what I should check first? Thanks in advance!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 4:14 AM

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ClearTheCode guidance (Dodge · Diagnostics & codes)

Summary: For 2018 Charger SXT - P0420 Code After Exhaust Work, work through these steps on your 2015+ vehicle:

  1. Confirm the symptom — note when it happens (cold start, highway, after fuel fill, etc.).
  2. Scan codes — save all pending/stored DTCs; don't clear until you've recorded them.
  3. Check TSBs & recalls — look up your VIN for open campaigns and known fixes.
  4. Inspect the obvious — related fuses, connectors, fluid level, and recent repairs.
  5. Test the common fix — follow model-specific service procedures; one change at a time.
  6. Escalate if needed — burning smell, no brakes, overheating, or stalling in traffic → shop visit.

Owner reported: Hey everyone, I'm hoping someone can help me out. I have a 2018 Dodge Charger SXT with about 80,000 miles on it. Recently, I had some exhaust work done, just a muffler delete, and now my Check Engine Light came on.

I hooked up my OBD-II scanner and it's showing a P0420 code, which I know means 'Catalyst System Efficiency Below Threshold (Bank 1)'. I'm really hoping it's not a bad catalytic conver…

This is educational guidance, not a substitute for hands-on diagnosis.

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