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Home >> Acura >> 2004 >> 3.5RL >> Repair and Diagnosis (Single Page) >> Engine Performance >> System >> Engine Performance System Self-Diagnostics >> Diagnostic Tests >> DTC P0420: Catalyst System Efficiency Below Threshold >> Diagnostic Procedure
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Diagnostic Procedure

  1. Perform PCM reset procedure. See PCM RESET PROCEDURE/CLEARING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. Start engine. Hold engine speed at 3000 RPM with no load and transmission in Park or Neutral until radiator fan comes on. Install SCS Service Connector (07PAZ-0010100) to Service Check Connector. See Figure .
  2. Test drive vehicle at 40-55 MPH for at least 2 minutes. Decelerate for at least 3 seconds with throttle completely closed. Then, reduce speed to 35 MPH and try to hold speed until readiness code comes on. If DTC P0420 sets, go to next step. If DTC P0420 does not reset, problem is intermittent. System is okay at this time.
  3. Remove three-way catalytic converter (TWC). Shine a flashlight into catalyst inlet while looking into catalyst outlet. Check for plugging, melting or cracking. Replace TWC if necessary.
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