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Home >> Cadillac >> 2006 >> DTS 4.6 9 >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - 4.6L - DTC P0403 To P1381 >> DTC P0420 >> Circuit/System Verification
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Circuit/System Verification

  1. If any other DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle for further diagnosis.
  2. Warm the catalyst by performing the following procedures:
    • Fully open the hood.
    • Place the transaxle in PARK for automatic transaxle.
    • Place the transaxle is NEUTRAL for manual transaxle, with clutch pedal depressed.
    • Set the parking brake.
    • Press and hold the service brake.
  3. Test the catalyst by performing the following procedures:
    • Idle the engine and place the vehicle in Drive to activate the diagnostic. Within 60 seconds, the Cmmd. A/F Equivalence ratio will transition rich for up to 7 seconds, and then may transition lean for up to 7 seconds.
    • Verify DTC P0420 has passed or failed this ignition cycle with the scan tool.
    • This diagnostic attempts 1 test during each valid idle period once the above conditions have been met for 5 seconds. This diagnostic attempts up to 6 tests during each drive cycle. The first test may be run after the initial warm up period of 6 minutes. Maintain engine speed between 2,000-3,000 RPM in park or neutral for 2 minutes. Allow the engine to return to a stabilized idle. Shift into drive for an automatic transmission while applying the brake pedal firmly. Between each subsequent test, maintain engine speed between 2,000-3,000 RPM in park or neutral for 2 minutes. Allow the engine to return to a stabilized idle. Shift into drive for an automatic transmission, without touching the accelerator in order for the test to run. The catalyst diagnostic should conclude and pass or fail by the end of the 6 tests.
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