P0420 Code on Your 2022 Mercedes-Benz GLE Explained
A P0420 trouble code on your 2022 Mercedes-Benz GLE means the engine control module has detected that the Bank 1 catalytic converter is losing its ability to process exhaust emissions efficiently. The 2022 GLE (W167) is available with the M264 2.0-liter turbocharged four-cylinder engine producing 255 horsepower in the GLE 350, or the M256 3.0-liter inline-six turbo with EQ Boost mild-hybrid technology generating 362 horsepower in the GLE 450.
The ECU uses upstream and downstream oxygen sensors to continuously evaluate catalytic converter performance. When the downstream sensor's voltage pattern begins to match the upstream sensor too closely, the system recognizes that the converter's internal catalyst material can no longer adequately process exhaust gases.
What Symptoms to Expect
- Check engine light on — steady illumination, not flashing
- Mild decrease in fuel economy
- Sulfur or rotten egg smell during acceleration
- Failed emissions test in states requiring inspection
- Potentially reduced engine performance if the converter is becoming clogged
Primary Causes for the 2022 GLE
1. Catalytic Converter Wear
With the 2022 GLE now a few years into service and potentially carrying 40,000-70,000 miles, normal catalytic converter wear is a leading cause. The M264 and M256 engines run hot, and the close-coupled converter position means it handles extreme thermal cycling with every cold start and drive cycle.
2. Failing Downstream Oxygen Sensor
The post-catalyst O2 sensor on the 2022 GLE can degrade with heat and age. A sensor that responds too slowly or reads inaccurately will trigger a false P0420 code. This is often the less expensive fix compared to a converter replacement.
3. Exhaust System Leak
Gasket failures, cracked flex pipes, or corroded exhaust connections near the catalytic converter can introduce ambient air. On the 2022 GLE, the exhaust routing under the large SUV body is exposed to road salt, moisture, and debris.
4. Engine Running Rich
If the fuel system is delivering more fuel than needed, the excess unburned fuel passes into the catalytic converter. This raises internal temperatures beyond design limits and damages the catalyst substrate. Check for related fuel trim or O2 sensor codes.
Diagnostic Process
- Scan for all codes using Mercedes XENTRY or a professional-grade OBD-II tool with Mercedes-Benz enhanced diagnostics.
- Analyze freeze frame data to understand operating conditions when the code triggered.
- Monitor live O2 sensor signals — compare upstream vs. downstream switching patterns in real time.
- Perform exhaust backpressure test to check for a clogged converter.
- Inspect physical exhaust components from the turbo outlet to the downstream sensor location.
Cost of Repairs
The 2022 GLE is a premium mid-size luxury SUV with correspondingly higher repair costs.
- Catalytic converter replacement: $2,400 – $5,000 with OEM parts and dealer labor.
- Downstream O2 sensor: $320 – $700 including parts and installation.
- Exhaust leak repair: $200 – $600.
- Rich-running condition repair: $300 – $1,500 depending on the root cause (injectors, fuel pressure regulator, etc.).
Should You Keep Driving?
The P0420 code is not a critical emergency on your 2022 GLE. You can continue driving normally, but plan to have it looked at within the next few weeks. The 2022 model may still be within the 4-year/50,000-mile basic warranty. The catalytic converter itself may be covered under the longer federal emissions warranty of 8 years/80,000 miles — check with your dealer before paying out of pocket.
Prevention Tips for GLE Owners
- Use premium fuel (91+ octane) consistently
- Avoid prolonged idling that creates excessive exhaust without sufficient heat
- Fix any engine performance issues immediately before they damage the converter
- Follow Mercedes-Benz service intervals for spark plugs, filters, and fluids
- Consider periodic highway drives to bring the converter to optimal operating temperature