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P0420 - Catalyst System Efficiency Below Threshold (Bank 1)

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P0420 - CATALYST SYSTEM EFFICIENCY BELOW THRESHOLD (BANK 1)

Description:  The powertrain control module (PCM) monitors the exhaust gas temperature (EGT) sensors to determine if a concern is present with the oxidation catalytic converter (OC). During a regeneration, the PCM expects the temperature across the OC to increase by a calibrated amount. The test fails when the increase in temperature is less than 40% of the expected maximum increase.
Possible Causes: 
  • Fuel injection concern
  • Fuel quality
  • Plugged OC
  • Oil contamination
  • Damaged OC
Diagnostic Aids:  Verify there are no concerns present with the fuel system and EGT sensors. Monitor the EGT11 and EGT12 PIDs to determine the temperature change across the OC.
Application  Key On Engine Off  Key On Engine Running  Continuous Memory 
All GO to PINPOINT TEST RA .