What Does Code P0420 Mean on a 2022 Jeep Grand Cherokee?
The P0420 code on your 2022 Jeep Grand Cherokee indicates that the Bank 1 catalytic converter is not efficiently processing exhaust gases. The 2022 Grand Cherokee launched the WL generation with the 3.6L Pentastar V6 (293 hp), available 5.7L Hemi V8 (357 hp), and the 2.0L turbo-4 plug-in hybrid in the 4xe model. The V6 and V8 models both have dual exhaust banks.
At a few years old with moderate mileage, this code could point to either a sensor issue, software calibration, or early converter wear depending on driving conditions and engine choice.
Common Symptoms
- Check engine light illuminated
- Mild fuel economy reduction
- Sulfur or rotten egg smell from exhaust
- Emissions test failure
- Usually no major drivability issues
Most Likely Causes on the 2022 Grand Cherokee
1. Failing Catalytic Converter
The Grand Cherokee, especially the Hemi V8 model, runs at high exhaust temperatures. Towing, which many Grand Cherokee owners do, accelerates converter wear. The Pentastar V6 converter can also degrade with higher mileage.
2. Faulty Downstream O2 Sensor
The post-converter oxygen sensor can become sluggish or contaminated over time. Both the V6 and V8 use similar sensor designs prone to the same aging issues.
3. PCM Software Issue
Stellantis has issued TSBs for various Grand Cherokee models addressing PCM calibration that can cause false P0420 codes. A software update may resolve the issue.
4. Exhaust Leak
Exhaust manifold gaskets on both the Pentastar V6 and Hemi V8 can develop leaks. The Hemi V8 is particularly known for exhaust manifold bolt failures that allow leaks.
How to Diagnose the P0420 Code
- Scan for all stored and pending codes
- Check for Stellantis TSBs for the 2022 Grand Cherokee
- Monitor live O2 sensor data on Bank 1
- Inspect for exhaust manifold leaks, especially on the Hemi V8 (look for broken manifold bolts)
- Test catalytic converter efficiency with temperature measurements
Repair Options and Costs
Professional Repair
- Catalytic converter (V6): $1,000–$2,000 parts and labor
- Catalytic converter (Hemi V8): $1,200–$2,500 parts and labor
- O2 sensor replacement: $180–$350
- Exhaust manifold bolt repair (Hemi): $400–$900
- PCM software update: $100–$200
DIY Considerations
O2 sensor replacement is feasible for DIYers. Exhaust manifold bolt repair on the Hemi requires specialized extraction tools. Check emissions warranty eligibility before paying out of pocket.
Cost Breakdown Summary
- OEM converter (V6): $600–$1,400
- OEM converter (V8): $800–$1,800
- O2 sensor (part): $70–$200
- Labor: $200–$700
- Diagnostic fee: $100–$150
Prevention Tips
- If towing frequently, allow cool-down periods to reduce exhaust heat stress
- For the Hemi V8, inspect exhaust manifold bolts periodically for breakage — a known issue
- Use mid-grade or premium fuel in the Hemi V8 for optimal combustion
- Follow Stellantis maintenance schedules for your specific engine
- Address any misfire or rough running conditions immediately