P0420 on Your 2024 Buick Enclave: Understanding the Code
A P0420 code on your 2024 Buick Enclave means the ECM has detected below-threshold efficiency from the Bank 1 catalytic converter. The completely redesigned 2024 Enclave features a new 2.5L turbocharged four-cylinder engine producing 328 horsepower — a significant upgrade from the previous generation's 3.6L V6. This new powertrain has a different exhaust configuration, and as a four-cylinder, there's a single exhaust bank.
On a brand-new redesigned vehicle, warranty covers this repair. Let's look at what might be causing the code.
Symptoms
- Check engine light on — Primary indicator
- Normal driving experience — The Enclave should drive fine
- Slight MPG change — Barely noticeable
- Possible exhaust odor — Faint sulfur smell
- Emissions failure — In testing states
Likely Causes
1. ECM Software Calibration
The 2024 Enclave is a first-year redesign with an all-new engine. Software calibrations for the catalyst monitoring system may need refinement as GM gathers real-world data. A software update is often the simplest and most common fix.
2. O2 Sensor Defect
A factory-defective downstream oxygen sensor can cause false P0420 readings. The new turbo engine's high exhaust temperatures can expose sensor defects early in the vehicle's life.
3. Catalytic Converter Issue
As a new-design converter for a new engine, manufacturing inconsistencies are possible. The close-coupled converter in the turbo exhaust system operates at extreme temperatures, making any deficiency apparent quickly.
4. Exhaust Assembly Issue
A gasket or connection not properly sealed during assembly of this new-generation vehicle can create a small leak affecting O2 sensor readings.
What to Do
- Visit your Buick dealer — This is a warranty repair.
- Ask about TSBs — First-year models often have early updates available.
- Continue normal driving — No restrictions needed.
- Keep records — Document all service visits.
Cost (If Out of Warranty)
- Software update: $0 under warranty ($100 – $150 otherwise)
- O2 sensor: $0 under warranty ($130 – $300 otherwise)
- Catalytic converter: $0 under warranty ($1,100 – $2,000 otherwise)
- Exhaust repair: $0 under warranty ($100 – $400 otherwise)
Safe to Drive?
Yes, completely. Your 2024 Enclave is safe with P0420. All safety features, the AWD system, and driver assistance technologies function normally. Schedule a convenient dealer appointment.
Prevention
- Use quality fuel — Top Tier gasoline helps the turbo engine run cleanly
- Follow the maintenance schedule — Especially important for a new-design engine
- Address all warning lights — Prompt attention prevents secondary damage
- Use recommended oil — Proper oil specification for the new turbo engine