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2018 XC90 T6 - P0420 Code and Check Engine Light

0

Nicole W. · rep 0 · May 22, 5:11 AM · 1 replies · solved · Question

Hey everyone,

My 2018 Volvo XC90 T6 Inscription just threw a Check Engine Light (CEL) yesterday. I hooked up 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. Fuel economy seems normal too. I've tried clearing the code, but it comes back after about 50-100 miles of driving.

Has anyone experienced this with their XC90? Is it likely a bad catalytic converter, or could it be something simpler like an O2 sensor? Any advice on what to check first would be greatly appreciated before I take it to the dealer.

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 5:11 AM

0

ClearTheCode guidance (Volvo · Diagnostics & codes)

Summary: For 2018 XC90 T6 - P0420 Code and Check Engine Light, work through these steps on your 2016+ 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,

My 2018 Volvo XC90 T6 Inscription just threw a Check Engine Light (CEL) yesterday. I hooked up 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. Fuel economy seems normal too. I've tried clearing the code, but it comes back after about 50-100 miles …

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

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