What Does Code P0420 Mean on a 2022 Jeep Grand Wagoneer?
A P0420 code on your 2022 Jeep Grand Wagoneer indicates the Bank 1 catalytic converter is not efficiently processing exhaust gases. The 2022 Grand Wagoneer was available with the 6.4L Hemi V8 producing 471 horsepower and 455 lb-ft of torque, paired with an 8-speed automatic and standard 4WD. This full-size luxury SUV is Jeep's flagship, and a P0420 on this vehicle demands quality diagnosis and repair.
The Hemi V8 runs at high exhaust temperatures, especially when towing the Grand Wagoneer's rated 9,850 pounds. This heat stress is a key factor in converter longevity.
Common Symptoms
- Check engine light illuminated
- Reduced fuel economy from the expected 13 city/18 highway MPG
- Sulfur or rotten egg smell from exhaust
- Emissions test failure
- Usually no noticeable power loss on the 471-hp Hemi
Most Likely Causes on the 2022 Grand Wagoneer
1. Failing Catalytic Converter
The 6.4L Hemi V8 produces extreme exhaust heat. Combined with the Grand Wagoneer's weight (over 6,000 lbs) and towing capability, the Bank 1 converter is under significant thermal stress. Degradation can begin earlier than expected.
2. Exhaust Manifold Bolt Issue
The Hemi V8 is well-known for exhaust manifold bolt failures. Broken bolts allow exhaust leaks that introduce unmetered air near the O2 sensors, triggering P0420. This is a common Hemi-specific issue.
3. Faulty Downstream O2 Sensor
The heated oxygen sensor downstream of the Bank 1 converter can fail due to extreme heat cycling on the Hemi V8. Sensor contamination from fuel additives or oil is also possible.
4. PCM Calibration
Stellantis may have software updates that address catalyst monitoring thresholds for the Grand Wagoneer's unique powertrain and weight class.
How to Diagnose the P0420 Code
- Inspect exhaust manifold bolts on the Hemi V8 — this is a known failure point
- Scan for all codes including misfire and O2 sensor codes
- Check for Stellantis TSBs specific to the Grand Wagoneer
- Monitor live O2 sensor data on Bank 1
- Test catalytic converter efficiency with temperature measurements
Repair Options and Costs
Professional Repair
- Catalytic converter replacement: $1,500–$3,000 parts and labor (luxury vehicle pricing)
- Exhaust manifold bolt repair: $500–$1,200
- O2 sensor replacement: $200–$400
- PCM software update: $100–$250
DIY Considerations
The Grand Wagoneer is a complex luxury vehicle. While technically possible, DIY work on this vehicle is not recommended due to the tight engine bay, expensive components, and warranty considerations. The 2022 model should still be under warranty.
Cost Breakdown Summary
- OEM converter (Hemi V8): $900–$2,200
- Aftermarket converter: $400–$900
- O2 sensor (part): $80–$220
- Labor: $400–$800
- Manifold bolt extraction: $300–$700
Prevention Tips
- Inspect exhaust manifold bolts periodically — Hemi bolt failure is a known issue
- If towing frequently, allow cool-down periods after long towing sessions
- Use mid-grade or premium fuel as recommended for the Hemi V8
- Follow Stellantis service intervals for the 6.4L engine
- Address any exhaust ticking noise immediately — it often indicates a manifold leak