What Does Code P0420 Mean on a 2022 Subaru Crosstrek?
A P0420 trouble code on your 2022 Subaru Crosstrek indicates that the Bank 1 catalytic converter is not performing to emissions standards. The 2022 Crosstrek offers two engine options: the base 2.0L FB20 boxer-4 producing 152 horsepower, and the Sport and Limited trims with the 2.5L FB25 boxer-4 making 182 horsepower. Both use the Lineartronic CVT with Symmetrical AWD.
The ECU monitors the catalytic converter's efficiency by comparing the upstream and downstream oxygen sensor signals. When the converter loses its ability to properly clean exhaust gases, both sensors start showing similar waveforms, and the ECU sets the P0420 code.
Common Symptoms
- Check engine light on
- Slight reduction in fuel economy
- Rotten egg or sulfur smell from the tailpipe
- Emissions inspection failure
- Usually no significant power loss
Most Likely Causes on the 2022 Crosstrek
1. Degrading Catalytic Converter
Both the 2.0L and 2.5L boxer engines can experience catalytic converter degradation. The Crosstrek's compact exhaust system design means the converter operates at high temperatures, which accelerates wear over time.
2. Faulty Downstream O2 Sensor
The rear O2 sensor on the Crosstrek can become sluggish or contaminated. The vehicle's higher ride height and off-road capability mean this sensor is exposed to more moisture and debris than a typical sedan.
3. Exhaust Header Gasket Leak
A classic Subaru boxer issue — the exhaust header gaskets can develop leaks that introduce extra oxygen into the exhaust stream, confusing the catalyst efficiency monitoring.
4. Oil Consumption Affecting Catalyst
The FB20 and FB25 engines have a reputation for oil consumption in some units. Oil vapor passing through the combustion process can contaminate the catalytic converter over time.
How to Diagnose the P0420 Code
- Run a full diagnostic scan for all stored and pending codes
- Check for Subaru TSBs related to P0420 on the 2022 Crosstrek
- Monitor live data from both O2 sensors on Bank 1
- Inspect the exhaust system for leaks at the headers, gaskets, and converter flanges
- Check oil consumption records — note if oil is being added between changes
Repair Options and Costs
Professional Repair
- Catalytic converter replacement: $800–$1,500 parts and labor
- Downstream O2 sensor: $140–$280
- Exhaust header gasket repair: $200–$450
- Spark plug replacement: $100–$220
DIY Considerations
The Crosstrek's higher ground clearance makes O2 sensor access easier than some vehicles. A sensor socket and jack stands are all you need. Converter and header gasket work is more complex. Check emissions warranty eligibility before spending money on repairs.
Cost Breakdown Summary
- OEM catalytic converter: $400–$1,000
- Aftermarket converter: $170–$430
- O2 sensor (part): $50–$130
- Labor for converter: $250–$500
- Diagnostic fee: $80–$150
Prevention Tips
- Monitor oil consumption closely on the FB20 or FB25 engine
- Use 0W-20 synthetic oil changed every 6,000 miles
- Replace spark plugs at the recommended 60,000-mile interval
- Avoid frequent cold starts without allowing the engine to reach operating temperature
- Use Top Tier gasoline for optimal combustion and reduced carbon buildup