P0420 on Your 2024 Acura TLX: What You Need to Know
A P0420 code on your 2024 Acura TLX means the ECM has detected reduced catalytic converter efficiency on Bank 1. The 2024 TLX continues with the 2.0L VTEC turbocharged four-cylinder (272 hp) in standard models and the 3.0L turbocharged V6 (355 hp) in the Type S. On a brand-new luxury sedan, this code is unexpected, but warranty coverage means it should be resolved at no cost.
Symptoms
- Check engine light on — Primary indicator
- Normal performance — Driving feel unchanged
- Minimal MPG impact — Barely measurable
- Possible faint exhaust odor — Sulfur smell
- Emissions failure — In testing states
Probable Causes
1. ECM Software Issue
Software calibration is a leading cause of P0420 on new vehicles. Honda/Acura regularly releases updates that adjust the catalyst efficiency monitoring thresholds. A PCM reflash may resolve the code without any parts replacement.
2. Defective O2 Sensor
A factory-defective downstream oxygen sensor can trigger false P0420 readings. Both the turbo-four and turbo V6 create extreme exhaust heat that can expose sensor defects early in the vehicle's life.
3. Catalytic Converter Manufacturing Defect
Rare but possible, a converter that wasn't manufactured to specification can underperform from new. The close-coupled design in the TLX's turbo exhaust system operates at extreme temperatures, making any manufacturing deficiency evident quickly.
4. Exhaust Assembly Issue
An improperly sealed gasket or loose connection from the factory can introduce an exhaust leak that affects O2 sensor readings. Common areas include the turbo outlet, downpipe flanges, and converter connections.
Recommended Actions
- Visit your Acura dealer — Warranty covers this repair.
- Request TSB check — Ask about software updates and known issues.
- Keep documentation — Note the date, mileage, and dealer interactions.
- Continue normal driving — No restrictions necessary.
Cost (If Out of Warranty)
- Software update: $0 under warranty ($100 – $150 otherwise)
- O2 sensor: $0 under warranty ($140 – $330 otherwise)
- Catalytic converter: $0 under warranty ($1,300 – $2,700 otherwise)
- Exhaust repair: $0 under warranty ($100 – $400 otherwise)
Safe to Drive?
Absolutely. Your 2024 TLX is completely safe with P0420. The code has zero impact on safety systems, SH-AWD, handling, or braking. Schedule a convenient dealer appointment.
Prevention
- Use premium fuel — Required for both TLX engines
- Follow maintenance minder alerts — Timely service prevents secondary issues
- Don't ignore other warning lights — Address all codes promptly
- Use Acura-recommended oil — Proper lubrication prevents engine deposits