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2017 CT6 V6 Misfire - P0304 and rough idle

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Mark S. · rep 0 · May 22, 3:56 AM · 1 replies · solved · Question

My 2017 Cadillac CT6, 3.6L V6 Luxury trim, recently started running really rough. The check engine light came on and it feels like it's misfiring, especially at idle and under light acceleration. I pulled the codes with my scanner and got a P0304, indicating a misfire on cylinder 4.

It's got about 75,000 miles on it. I'm wondering if it's just a spark plug or something more serious. Any common issues with these engines causing misfires? I'd appreciate any advice before I take it to a shop.

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 3:56 AM

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ClearTheCode guidance (Cadillac · Diagnostics & codes)

Summary: For 2017 CT6 V6 Misfire - P0304 and rough idle, 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: My 2017 Cadillac CT6, 3.6L V6 Luxury trim, recently started running really rough. The check engine light came on and it feels like it's misfiring, especially at idle and under light acceleration. I pulled the codes with my scanner and got a P0304, indicating a misfire on cylinder 4.

It's got about 75,000 miles on it. I'm wondering if it's just a spark plug or something more serious. Any common is…

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

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