LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Acura >> 2003 >> 3.2CL Base >> Repair and Diagnosis >> Engine Performance >> System >> Engine Performance System Self-Diagnostics >> Diagnostic Tests >> DTC P0420: Catalyst System Efficiency Below Threshold >> 3.2CL
April 5, 2026: LEMON Manuals is launched! Read the announcement.

DTC P0420: Catalyst System Efficiency Below Threshold: 3.2CL

  1. Perform PCM reset procedure. See PCM RESET PROCEDURE/CLEARING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. Start engine and run at 3000 RPM, with no load (in park or neutral) until radiator fan comes on.
  2. Connect scan tool to DLC. Test drive vehicle at 40-55 MPH for about 2 minutes. Decelerate with throttle completely closed for at least 3 seconds. Reduce speed to 35 MPH and try to hold until scan tool indicates FAIL or PASS as Three Way Catalytic Converter (TWC) test result. If test result is FAIL, check TWC and replace if necessary. If test result is PASS, problem is intermittent. System is okay at this time.
scientia non olet · About LEMON Manuals