P0420 on Toyota Vitz (SCP10): Catalytic converter efficiency below threshold

Short answer: P0420 means “Catalytic converter efficiency below threshold”. The car’s computer has found a fault in the Emissions - catalyst system and turns on the Check engine light (MIL). First check: check for exhaust leaks.

Code

P0420

System

Emissions - catalyst

Dashboard light

Check engine light (MIL)

Also sold as

Toyota Yaris, Toyota Echo (XP10)

Applies to

1SZ-FE (by platform)

Confidence

medium (Toyota Echo 1999–2002 factory diagnostics, same XP10 platform; not confirmed on JDM 1SZ-FE)

Source

carmanualsclub.com

Likely causes

1. Catalytic converter
2. Rear oxygen sensor
3. Exhaust leak

What to check, in order

1. Check for exhaust leaks
2. Check rear oxygen sensor
3. Replace catalytic converter if worn

Related on this car

• All fault codes for this car
• Warning lights
• Where the parts are (parts map)
• Common problems

Same code on other cars

• P0420 · Toyota Passo (1st gen)
• P0420 · Toyota Corolla (11th gen, E170)
• P0420 · Toyota Corolla (10th gen, E140)
• P0420 · Honda City (5th gen, GM2)
• P0420 · Honda Civic (10th gen, FC)
• P0420 · Suzuki Wagon R (Pakistan, K10B)
• P0420 on all cars compared

← P0340/12 P0500/42 →

Clearing the code does not fix the fault. If it comes back, the problem is still there. For brakes, airbags and steering, see a trained mechanic.