Understanding P0420 on Your 2024 Dodge Hornet
A P0420 diagnostic trouble code on your 2024 Dodge Hornet means the powertrain control module has detected below-threshold efficiency from the Bank 1 catalytic converter. The 2024 Hornet continues with the same powertrain options: the 2.0L turbocharged four-cylinder (268 hp) in the GT and the 1.3L turbo plug-in hybrid (288 hp combined) in the R/T. Both use catalytic converters to meet emissions requirements, and both can set a P0420 code.
Finding this code on a brand-new vehicle is frustrating, but the silver lining is comprehensive warranty coverage. Let's investigate what might be happening.
What Symptoms Come With P0420?
- Check engine light on — The main indicator of this code
- Minimal fuel economy change — May drop 1-2 MPG
- Possible sulfur odor — From the exhaust
- Normal driving experience — Performance typically unaffected
- Emissions test failure — If your state requires it
Likely Causes for the 2024 Hornet
1. Software Calibration Issue
The Hornet uses Stellantis software that monitors catalyst efficiency through O2 sensor comparisons. On newer vehicles, overly aggressive monitoring thresholds can trigger premature P0420 codes. A PCM reflash with updated calibration data often resolves this without any parts needing replacement.
2. Defective O2 Sensor
The downstream oxygen sensor on Bank 1 is responsible for triggering this code. A sensor that left the factory with a defect or that has been contaminated can send incorrect readings to the PCM, resulting in a false P0420. This is a quick and inexpensive fix.
3. Catalytic Converter Manufacturing Issue
The close-coupled catalytic converter in the Hornet's turbo engine exhaust system operates at extreme temperatures. If the converter wasn't manufactured to spec — insufficient catalyst coating, damaged substrate, or contamination — it will underperform and trigger the code.
4. Exhaust Assembly Defect
A gasket that wasn't seated properly or a connection that wasn't fully tightened during assembly can create a small exhaust leak. This leak introduces ambient air near the O2 sensor, causing false low-efficiency readings.
What Should You Do?
- Schedule a dealer appointment — This is a warranty repair on a 2024 model. Don't attempt to fix it yourself.
- Note when the light appeared — Record the mileage and driving conditions when the code first triggered. This helps the technician diagnose the issue.
- Ask about TSBs — Request that the dealer check for any Technical Service Bulletins specific to the 2024 Hornet's emissions system.
- Keep driving normally — The code doesn't require any changes to your driving habits.
Cost Estimates (If Out of Warranty)
- PCM software update: $0 under warranty ($100 – $150 out of warranty)
- O2 sensor replacement: $0 under warranty ($120 – $280 out of warranty)
- Catalytic converter replacement: $0 under warranty ($1,000 – $1,900 out of warranty)
- Exhaust leak repair: $0 under warranty ($100 – $350 out of warranty)
Is It Safe to Drive?
Completely safe. A P0420 code has zero impact on the safety of your 2024 Hornet. The brakes, steering, stability control, and all other safety systems are unaffected. Continue driving normally while you schedule your warranty appointment.
Keeping Your Hornet's Exhaust System Healthy
- Use the recommended fuel grade — Premium fuel helps the turbo engine run cleanly
- Follow the maintenance schedule — Oil changes and service at the recommended intervals
- Don't modify the exhaust system — Aftermarket exhaust components can trigger P0420 and void warranty
- Address all engine codes quickly — Small issues can cascade into converter damage