What Does P0420 Mean on a 2022 Buick Enclave?
A P0420 code on your 2022 Buick Enclave indicates the engine control module has detected reduced Bank 1 catalytic converter efficiency. The 2022 Enclave is powered by a 3.6L V6 engine producing 310 horsepower, paired with a 9-speed automatic transmission and available all-wheel drive. As a V6, the engine has two exhaust banks, and P0420 specifically targets Bank 1 — the side of the engine with cylinder number one.
The Enclave shares its platform and powertrain with other GM three-row crossovers, so there's a well-established service history for this engine. Let's explore the common causes.
Symptoms
- Check engine light on — Primary indicator
- Slight fuel economy drop — Possibly 1-2 MPG less
- Faint sulfur smell — From the exhaust
- Normal driving behavior — The Enclave should drive smoothly
- Emissions test failure — In testing states
Common Causes on the 2022 Enclave
1. Catalytic Converter Degradation
The 3.6L V6's catalytic converter can degrade over time due to normal wear, especially if the Enclave sees frequent short trips or stop-and-go driving that doesn't allow the converter to reach optimal operating temperature consistently. Family-duty use with frequent short trips is common with the Enclave.
2. Downstream O2 Sensor Problem
The Bank 1 downstream oxygen sensor monitors converter output. A sluggish, contaminated, or electrically faulty sensor can produce incorrect readings. On the Enclave, this sensor is accessible from underneath the vehicle.
3. Exhaust Leak
The exhaust manifold gaskets, converter connections, and pipe joints can develop leaks from thermal cycling. A leak before the downstream O2 sensor introduces ambient air that triggers false P0420 readings.
4. Engine Timing or Fuel System Issue
GM's 3.6L V6 is known for occasional timing chain stretch in some applications. While not a direct P0420 cause, altered valve timing can affect combustion efficiency and exhaust composition, indirectly stressing the catalytic converter.
Diagnostic Steps
- Full code scan — Check for additional codes alongside P0420.
- O2 sensor monitoring — Compare Bank 1 upstream and downstream waveforms.
- GM TSB check — Your dealer can search for applicable Technical Service Bulletins.
- Exhaust inspection — Check all connections and gaskets for leaks.
Repair Costs
- Catalytic converter: $1,000 – $2,200 for GM/OEM parts
- O2 sensor: $130 – $300
- Exhaust leak repair: $100 – $400
- Timing chain service: $1,200 – $2,500 if applicable
Safe to Drive?
Yes, your 2022 Enclave is safe to drive with P0420. The family SUV will continue to function normally for daily driving, school runs, and family trips. Check your warranty coverage and schedule a dealer visit.
Prevention
- Use quality fuel — Top Tier gasoline keeps the fuel system clean
- Follow GM's maintenance schedule — Regular service prevents issues
- Let the engine warm up — Especially on short trips, allow the converter to reach operating temperature
- Address other codes promptly — Misfires and fuel system problems damage converters