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Home >> GMC >> 2003 >> Safari Van Cargo, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 398 (Engine Controls - Self Diagnostics - 4.3L) >> Diagnostic Tests >> DTC P0420: TWC System - Low Efficiency - Bank 1 & DTC P0430: TWC System - Low Efficiency - Bank 2 >> Test Description

Test Description

WARNING: This page is about a different car, the 2003 GMC Sierra and 2003 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.

The number below refers to the step number in the diagnostic procedure.

  1. 3

    This step inspects for conditions that can cause the 3-way catalytic converter efficiency to appear degraded.
  2. A catalytic converter which has been discolored may be due to an engine running rich, lean or had a previous sever misfire. Verifying the fuel trim percentages may be of assistance in determining if such a condition exists.

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