What Does Code P0420 Mean on a 2024 Jeep Grand Cherokee?
A P0420 code on your 2024 Jeep Grand Cherokee indicates the Bank 1 catalytic converter is not cleaning exhaust gases efficiently. The 2024 Grand Cherokee (WL platform) offers the 3.6L Pentastar V6 with 293 horsepower as the standard engine, the 5.7L Hemi V8 with 357 horsepower, and the 2.0L turbocharged inline-4 in the 4xe plug-in hybrid. P0420 targets Bank 1 on whichever engine your model has.
On a brand-new 2024 Grand Cherokee, this code is unusual and almost certainly indicates a warranty-covered issue. The vehicle should be taken directly to a Jeep dealer.
Common Symptoms
- Check engine light on
- Minimal drivability changes
- Slight fuel economy decrease
- Emissions test failure
- Possible faint sulfur smell
Most Likely Causes on the 2024 Grand Cherokee
1. PCM Software Calibration
On a new Grand Cherokee, a PCM software update is the most common fix. Stellantis (Jeep's parent company) regularly issues calibration updates for catalyst monitoring on the Pentastar V6 and Hemi V8.
2. Faulty Downstream O2 Sensor
A manufacturing defect in the downstream oxygen sensor can produce false P0420 readings. Both the V6 and V8 use similar sensor types that can have quality control issues.
3. Exhaust Assembly Issue
A factory assembly defect such as an improperly seated gasket or loose exhaust connection can cause a leak that triggers the code.
4. Catalytic Converter Manufacturing Defect
Rare on a new vehicle, but a defective converter would be fully covered under Jeep's warranty.
How to Diagnose the P0420 Code
- Take the vehicle to a Jeep dealer for warranty service
- Dealer checks for TSBs and PCM software updates
- Live data analysis of upstream and downstream O2 sensors
- Exhaust system inspection for assembly defects
- Converter efficiency testing if needed
Repair Options and Costs
Warranty Repair (Recommended)
- PCM software update: No cost
- O2 sensor replacement: No cost
- Exhaust repair: No cost
- Catalytic converter replacement: No cost
Out-of-Warranty Reference
- Converter replacement (V6): $1,100–$2,000
- Converter replacement (Hemi V8): $1,300–$2,500
- O2 sensor: $180–$350
DIY Considerations
Do not attempt DIY repairs on a 2024 Grand Cherokee. Let the dealer handle all warranty-covered work.
Cost Breakdown Summary
- Under warranty: $0
- OEM converter (V6): $600–$1,400
- OEM converter (V8): $800–$1,800
- O2 sensor (part): $70–$200
Prevention Tips
- Follow Stellantis maintenance schedules from day one
- Use the recommended engine oil grade for your specific engine
- Keep all service records for warranty claims
- Address check engine lights immediately
- Use quality fuel — the Hemi V8 benefits from mid-grade or premium fuel