Inefficient Catalytic Converter(s), Defective Front or Rear Oxygen Sensor(s), Misfiring engines
On Audi vehicles, P0420 is logged when the ECU detects a fault in the catalytic converter: “Inefficient Catalytic Converter(s), Defective Front or Rear Oxygen Sensor(s), Misfiring engines”. P0420 is a generic SAE code — see the universal P0420 page too.
Typical triggers for a catalytic converter code like P0420 include faulty or ageing sensors, wiring/connector faults, a clogged or removed component, or a value drifting outside the ECU's expected window. Symptoms range from a check-engine light only, to limp mode, rough running, higher consumption or failed emissions tests.
When a Audi has had hardware changed for off-road/motorsport use (for example a removed DPF or EGR), the related monitor must be disabled in the ECU map or the code re-appears. Softechpro Solutions performs DPF/EGR/AdBlue/DTC off and recalculates the checksum, so codes like P0420 stay cleared after the flash. Genuine faults should always be repaired, not just hidden.
Softechpro Solutions does DPF/EGR/AdBlue/DTC off + checksum for 260+ ECU families — from €98.99/mo.
See pricing Ask on WhatsApp