Understanding P0420 on Your 2024 Acura RDX
A P0420 code on your 2024 Acura RDX means the ECM has detected that the catalytic converter isn't operating at expected efficiency levels. The 2024 RDX continues with the proven 2.0L VTEC turbocharged four-cylinder engine producing 272 horsepower. As an inline-four, there's one exhaust bank and one catalytic converter in the main exhaust path, making diagnosis straightforward compared to V-configuration engines.
On a vehicle this new, warranty should cover whatever repair is needed. Let's look at the possible causes.
Symptoms
- Check engine light on — The primary symptom
- Normal performance — The RDX should drive fine
- Minimal MPG change — Hardly noticeable
- Possible exhaust smell — Faint sulfur odor
- Emissions failure — In testing states
Likely Causes
1. PCM Software Calibration
Honda and Acura regularly refine their PCM software for emissions monitoring. The 2024 RDX may have catalyst monitoring parameters that benefit from a software update. This is a common first-step fix for new vehicles with P0420.
2. O2 Sensor Defect
A factory-defective downstream O2 sensor can trigger false P0420 readings. The turbo engine's high exhaust temperatures can expose sensor defects quickly. A simple sensor swap resolves this issue.
3. Catalytic Converter Defect
The close-coupled converter in the RDX's turbo exhaust system may have a manufacturing defect — insufficient catalyst coating, substrate damage, or contamination from the production process. This is a full warranty repair.
4. Exhaust Leak
An improperly sealed gasket or connection in the turbo exhaust path can create a small leak. This is most common at the turbo outlet, downpipe connections, or converter flanges.
What to Do
- Schedule an Acura dealer visit — This is a warranty repair.
- Ask about TSBs — Technical Service Bulletins may address this specific issue.
- Keep records — Document the issue for your service history.
- Drive normally — No changes needed to your routine.
Cost Estimates (If Out of Warranty)
- PCM software update: $0 under warranty ($100 – $150 otherwise)
- O2 sensor: $0 under warranty ($130 – $300 otherwise)
- Catalytic converter: $0 under warranty ($1,200 – $2,300 otherwise)
- Exhaust leak: $0 under warranty ($100 – $400 otherwise)
Safe to Drive?
Yes, completely. Your 2024 RDX is safe to drive with P0420. The SH-AWD system, AcuraWatch safety suite, and all driving systems function normally. Continue driving while you schedule a warranty repair.
Prevention
- Use premium fuel — Acura recommends premium for the turbo engine
- Follow the maintenance minder — Acura's built-in service reminder system
- Address all codes promptly — Small issues can damage the converter
- Use Acura-recommended oil — Proper oil prevents engine deposits