Understanding P0420 on Your 2022 Lexus IS
A P0420 code on your 2022 Lexus IS means the ECM has detected that the Bank 1 catalytic converter isn't operating at full efficiency. The 2022 IS received a significant refresh with sharper styling and improved dynamics. It's available with the IS 300 using a 2.0L turbocharged four-cylinder (241 hp) in rear-wheel drive or a 3.5L V6 (260 hp) in all-wheel drive, and the IS 350 with a 3.5L V6 (311 hp). The IS 500 also debuted with a naturally aspirated 5.0L V8 (472 hp), though that model uses a different exhaust configuration.
The 2022 IS is still relatively new, so let's look at what might be triggering this code and how to handle it.
Symptoms
- Check engine light illuminated — Primary symptom
- Minor fuel economy change — Possibly 1-2 MPG reduction
- Faint sulfur odor — From the exhaust area
- Normal driving dynamics — The IS should handle and accelerate normally
- Emissions test failure — In applicable states
Common Causes for the 2022 IS
1. Downstream O2 Sensor Issue
On a vehicle this age, a faulty or prematurely aging downstream oxygen sensor is a strong possibility. The IS's sport-oriented exhaust system generates significant heat, particularly during spirited driving, which can stress the sensor. If the sensor sends inaccurate readings, the ECM interprets this as poor converter efficiency.
2. Software Calibration
Toyota and Lexus occasionally release ECM software updates that refine catalyst monitoring thresholds. The 2022 IS refresh may have calibration settings that benefit from a software update, particularly for the 2.0L turbo engine where exhaust characteristics differ from the V6 models.
3. Catalytic Converter Defect
Manufacturing defects can occur even on premium brands like Lexus. An improperly manufactured converter with insufficient catalyst coating or damaged substrate can trigger P0420 early in the vehicle's life. This would be a warranty repair.
4. Exhaust System Leak
Exhaust leaks at gaskets, flanges, or weld points can introduce air near the downstream O2 sensor. On the IS, check the exhaust manifold connections, converter inlet and outlet, and any midpipe joints for signs of leaking.
Diagnosis Steps
- Check for TSBs — Have your Lexus dealer search for any applicable Technical Service Bulletins.
- Comprehensive code scan — Look for additional codes alongside P0420.
- O2 sensor waveform analysis — Compare Bank 1 upstream and downstream sensor patterns.
- Exhaust inspection — Physical inspection for leaks and damage.
Repair Costs
- Downstream O2 sensor: $150 – $360 (parts and labor)
- ECM software update: $0 – $150
- Catalytic converter replacement: $1,400 – $2,900 for OEM Lexus parts
- Exhaust leak repair: $100 – $400
Is It Safe to Drive?
Yes, your 2022 Lexus IS is safe to drive with a P0420 code. The code doesn't affect the sport sedan's handling, braking, or safety systems. Since the vehicle should still be under warranty, schedule a dealer visit sooner rather than later for a potentially no-cost repair.
Prevention
- Use premium fuel — The IS engines require premium gasoline for optimal combustion
- Fix misfires right away — Misfires are the fastest way to kill a catalytic converter
- Maintain regular service — Follow the Lexus maintenance schedule
- Warm up before hard driving — Let the exhaust reach operating temperature before track days or spirited driving