Fault Code: P0421 Warm Up Catalyst Efficiency Below Threshold (Bank 1)

09/09/2022 0 Comments

Symptoms:

  • The Check Engine Light will be illuminated
  • The may not start
  • The engine may lack power or hesitate upon acceleration
  • Strange noises may be heard whilst driving

Causes:

  • A faulty catalytic converter
  • A faulty oxygen sensor
  • Damaged oxygen sensor circuitry
  • A faulty powertrain control module

Possible Solutions:

  • Repairing or replacing wiring that is associated with the oxygen sensor
  • Replacing the oxygen sensor
  • Replacing the powertrain control module
  • Replacing the catalytic converter
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