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Home >> GMC >> 2006 >> Sierra 1500 HD, RWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 1645 (Engine Control System & Fuel System - 4.8L, 5.3L, 6.0L, 6.2L - DTC P0300 To DTC P1175) >> DTC P0420 or P0430 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2010 GMC Sierra, 2010 GMC Cab & Chassis Sierra, 2010 Chevrolet Silverado, and 2010 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
    CAUTION: Refer to Heated Oxygen Sensor Resistance Learn Reset Caution .
    NOTE: A new converter with less than 100 miles on it may set DTC P0420 or P0430 due to out-gassing of the internal matting. Operating the vehicle at highway speeds for approximately 1 hour may correct the condition.
  1. Engine idling, observe the DTC information with a scan tool. Verify there are no HO2S or misfire DTCs set.
  2. Verify the following conditions do not exist with the catalytic converter:
    • Dents
    • A severe discoloration caused by excessive temperatures
    • An internal rattle caused by damaged catalyst substrate
    • Restrictions
    • If a condition is found, replace the catalytic converter.
  3. Verify the following conditions do not exist with the exhaust system:
    • Leaks
    • Physical damage
    • Loose or missing hardware
    • Improperly torqued HO2S
    • If a condition is found, repair the exhaust system.
  4. Verify the following conditions do not exist with the HO2S 2:
    • A grounded wiring harness
    • Damage
    • If a condition is found, replace the HO2S 2.
  5. If no physical condition is detected and the HO2S 2 is as active as the HO2S 1 after operating the engine at 1,500 RPM for 1 minute and then returning to a stabilized idle, then replace the catalytic converter.
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