P0420
Catalyst System Efficiency Below Threshold (Bank 1)
What does P0420 mean?
The DTC P0420 (Catalyst System Efficiency Below Threshold (Bank 1)) is a fault code stored by the ECU when it detects a cat efficiency condition in the emissions subsystem. It is commonly seen on European and Asian vehicles using Bosch, Continental, Siemens or Denso ECUs.
Common causes of P0420
- Aging catalytic converter
- Failed downstream O2 sensor
- Exhaust leak before cat
- Engine running rich/lean
How to fix P0420
Confirm with live O2 sensor data. If cat is dead, replace it. If sensors are the issue, replace them. DaVinci can disable the readiness monitor for cat efficiency on tuned/decatted cars.
Tuning approach with DaVinci Deluxe · Cloud Edition
For P0420, DaVinci Deluxe · Cloud Edition offers the following ECU map adjustments and software solutions:
- Catalyst monitor OFF
- O2 sensor heater monitor adjust
- Lambda regulation tweak
Need to fix P0420 on your ECU?
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