What Does Code P0420 Mean on a 2024 Jeep Grand Wagoneer?
A P0420 code on your 2024 Jeep Grand Wagoneer indicates the Bank 1 catalytic converter is not meeting efficiency standards. The 2024 Grand Wagoneer transitioned to the 3.0L Hurricane twin-turbocharged inline-6 engine, available in standard tune (420 hp, 468 lb-ft) and high-output (510 hp, 500 lb-ft), replacing the previous 6.4L Hemi V8. This new engine pairs with an 8-speed automatic and standard 4WD.
On a brand-new 2024 model with a new engine platform, P0420 is uncommon and should be warranty-covered. The twin-turbo inline-6 represents a completely different exhaust architecture than the Hemi V8.
Common Symptoms
- Check engine light on
- Minimal performance changes on the 420+ hp engine
- Slight fuel economy decrease
- Emissions test failure
- Possible faint exhaust odor
Most Likely Causes on the 2024 Grand Wagoneer
1. PCM Software Calibration
The Hurricane twin-turbo I6 is a relatively new engine platform. First-year implementations in the Grand Wagoneer may require PCM calibration adjustments for catalyst efficiency monitoring.
2. Turbo System-Related Issue
The twin-turbo configuration adds complexity to the exhaust path. Wastegate calibration, boost leaks, or turbo-related issues can alter the air-fuel ratio and affect converter performance readings.
3. Faulty O2 Sensor
A manufacturing defect in the downstream oxygen sensor is a straightforward warranty fix. The high exhaust temperatures from the twin-turbo setup can stress sensor components.
4. Catalytic Converter or Exhaust Assembly Defect
A factory defect in the converter or exhaust assembly — fully warranty-covered on a 2024 model.
How to Diagnose the P0420 Code
- Take the vehicle to a Jeep dealer — all diagnosis is warranty-covered
- Dealer checks for TSBs for the Hurricane engine in the Grand Wagoneer
- ECU software version verification and update
- Twin-turbo system inspection including boost and wastegate function
- O2 sensor and converter efficiency testing
Repair Options and Costs
Warranty Repair (Recommended)
- All P0420-related repairs: No cost under warranty
Out-of-Warranty Reference (Luxury Pricing)
- Catalytic converter replacement: $1,800–$3,500
- O2 sensor replacement: $220–$450
- Turbo system diagnosis: $200–$500
- Software update: $150–$300
DIY Considerations
Do not attempt DIY work on a 2024 Grand Wagoneer. This is a premium luxury vehicle under full warranty. All work should be handled by an authorized dealer.
Cost Breakdown Summary
- Under warranty: $0
- OEM converter (future reference): $1,200–$2,500
- O2 sensor (future reference): $100–$250
Prevention Tips
- Follow Stellantis premium service intervals for the Hurricane twin-turbo engine
- Use premium fuel as recommended for the twin-turbo I6
- Allow turbo cool-down after towing or spirited driving
- Keep all dealer service records for warranty documentation
- Address check engine lights promptly at the dealership