Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
DTC P0420: Catalyst System Efficiency Below Threshold: 3.2TL
2004 Acura 3.5RLSECTION 3.2TL
WARNING: This page is about a different car, the 2003 Acura 3.2TL and 2003 Acura 3.2CL. However, it is still accessible from the selected car via links, so may be relevant.
- Perform PCM reset procedure. See PCM RESET PROCEDURE/CLEARING DIAGNOSTIC TROUBLE CODES under SELF-DIAGNOSTIC SYSTEM. Start engine and run at 3000 RPM, with no load (in park or neutral) until radiator fan comes on. Drive about 10 minutes on highway without stopping. Speed can vary. With transmission in "D5" position, drive at steady speed between 50 and 62 MPH for 30 seconds. Repeat three times, closing throttle completely for 1-2 seconds between each repetition. If engine is stopped during this part of procedure, start over with road test.
- Check for Three-way Catalytic Converter (TWC) test results with scan tool. If FAIL is indicated, check TWC. Replace if necessary. If PASS is indicated, problem is intermittent, system is okay at this time.
RENDER: 1.0x
NO RELATED
Recommended Tools & Savings
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Affiliate disclosure: We may earn a commission at no extra cost to you.
When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.