P0420 Code on Your 2023 Dodge Challenger: What It Means
A P0420 code on the 2023 Dodge Challenger — the final year of this legendary muscle car — means the PCM has detected that the Bank 1 catalytic converter isn't operating at full efficiency. The 2023 Challenger is available with the 3.6L Pentastar V6 (303 hp), 5.7L HEMI V8 (375 hp), 6.4L HEMI V8 (485 hp), and the supercharged 6.2L HEMI (up to 807 hp in the Demon 170). Since this is the last model year for the current Challenger, many owners want to keep these cars in top condition.
Getting a P0420 on a vehicle this new is frustrating, but the upside is that warranty coverage should handle most repairs. Let's explore what might be triggering the code.
Symptoms You May Notice
- Illuminated check engine light — The primary symptom
- Slight fuel economy reduction — Perhaps 1-2 MPG less
- Faint sulfur odor — From the exhaust area
- No noticeable performance loss — Drivability typically unaffected
- Emissions test failure — In testing states
What's Causing the P0420 on Your 2023 Challenger
1. Oxygen Sensor Malfunction
On a vehicle this new, a faulty downstream O2 sensor on Bank 1 is one of the most likely culprits. These sensors can fail prematurely due to manufacturing defects, contamination from engine oil vapor, or electrical issues. When the sensor reports incorrect data, the PCM interprets it as poor converter performance.
2. PCM Software Issue
Chrysler has a history of releasing software updates for emissions monitoring systems. The 2023 Challenger, being the final model year, may have catalyst monitoring calibrations that are overly sensitive. A PCM reflash from your dealer may resolve the code entirely without any parts being replaced.
3. Defective Catalytic Converter
Although rare on a brand-new vehicle, manufacturing defects can happen. The catalytic converter's internal substrate may not have been properly coated, or it could have been damaged during shipping or installation. This is fully covered under warranty.
4. Exhaust Leak
Even new vehicles can develop exhaust leaks, especially at gasket connections and flanges. A small leak near the downstream O2 sensor location can introduce ambient oxygen that causes false readings.
How to Diagnose
- Check for TSBs first — Before any other diagnostics, have your dealer check for Technical Service Bulletins specific to the 2023 Challenger's emissions system.
- Scan for all codes — Look for additional diagnostic trouble codes that might point to a secondary issue.
- Monitor O2 sensor data — Compare upstream and downstream O2 sensor waveforms on Bank 1. A failing converter shows similar wave patterns on both sensors.
- Visual exhaust inspection — Check for leaks, damage, or loose connections throughout the exhaust system.
Repair Costs
- Catalytic converter replacement: $1,200 – $2,800 (should be warranty-covered)
- Downstream O2 sensor: $125 – $300 (likely warranty-covered)
- PCM software update: $0 – $150 (typically free under TSB)
- Exhaust leak repair: $100 – $400 (may be warranty-covered)
Is It Safe to Drive?
Yes, absolutely. The P0420 code does not impact the safety or drivability of your 2023 Challenger. You can continue driving it normally. However, since you're almost certainly within warranty coverage, there's no reason to wait — schedule a dealer appointment and get it fixed for free.
Keeping Your Challenger's Exhaust System Healthy
- Address engine codes promptly — Misfires can rapidly destroy catalytic converters
- Use the right fuel — Premium fuel is recommended for all HEMI engines
- Follow the maintenance schedule — Regular service keeps the engine running clean
- Warm up before spirited driving — Let the engine and exhaust reach operating temperature first