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Home >> Hummer >> 2008 >> H2 4D Utility Wagon >> Repair and Diagnosis >> External Pages >> Different car >> Section 514 (Engine Controls/Fuel - Hybrid (LZ1) - DTC P0351 To DTC P3449 And Diagnostic Information And Procedures) >> Diagnostic Information and Procedures >> DTC P0420 or P0430 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2012 GMC Yukon, 2012 Chevrolet Tahoe, and 2012 Cadillac Escalade. However, it is still accessible from the selected car via links, so may be relevant.
CAUTION:

Refer to Three-Way Catalytic Converter Damage Caution .

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 h may correct the condition.

  1. Ignition ON, observe the DTC information with a scan tool. Verify that no HO2S or misfire DTCs are set.
  2. Inspect the catalytic converter for the following conditions:
    • Dents
    • Severe discoloration caused by excessive temperatures
    • Road damage
    • An internal rattle caused by damaged catalyst substrate
    • Restrictions
      • If a condition is found, replace the catalytic converter.
  3. Inspect the exhaust system for the following conditions:
    • Leaks-Refer to Exhaust Leakage .
    • Physical damage
    • Loose or missing hardware
    • Improperly torqued HO2S
    • Restrictions-Refer to Restricted Exhaust .
      • If a condition is found, repair the exhaust system.
  4. Inspect the post catalyst HO2S for the following conditions:
    • A grounded or damaged wiring harness
    • Damaged sensor
      • If a condition is found, replace the post catalyst HO2S.
  5. If all physical conditions test normal, test or replace the catalytic converter.
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