P0420 on Toyota Passo (KGC10): Catalyst System Efficiency Below Threshold (Bank 1)
Short answer: P0420 means “Catalyst System Efficiency Below Threshold (Bank 1)”. The car’s computer has found a fault in the Emissions - catalyst system and turns on the Check engine light (MIL). First check: check exhaust leaks, rear O2 live data, then catalyst.
- Code
- P0420
- System
- Emissions - catalyst
- Dashboard light
- Check engine light (MIL)
- Also sold as
- Daihatsu Boon, Daihatsu Sirion (M300)
- Applies to
- Unverified for 1st-gen Passo/Boon; 1KR-FE (toyota-club.net list covers all 1KR-FE variants; 1st-gen KGC10/15 fitment not individually confirmed)
- Confidence
- low - NOT in Daihatsu M300 factory chart (B8-52..55); likely later-gen/Toyota-built 1KR only
- Source
- toyota-club.net · motordata.net · pakwheels.com · stuff.jaygroh.com
Symptoms and when it is set
- Usually MIL only
Likely causes
- Aged catalyst, lazy rear O2 sensor, exhaust leak before rear sensor, prior misfire
What to check, in order
- Check exhaust leaks, rear O2 live data, then catalyst
Related on this car
- Blocked catalytic converter
- All fault codes for this car
- Warning lights
- Where the parts are (parts map)
- Common problems
Same code on other cars
- P0420 · Toyota Vitz (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
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.