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Home >> GMC >> 2003 >> Safari Van Cargo, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 401 (Engine Controls - Self Diagnostics - 8.1L) >> Diagnostic Tests >> DTC P0420: : TWC System - Low Efficiency - Bank 1 & DTC P0430: TWC System - Low Efficiency - Bank 2 >> Test Description

Test Description

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The numbers below refer to the step numbers in the diagnostic procedure.

  1. 6

    This step inspects for conditions than can cause the 3-way catalytic converter efficiency to appear degraded.

  2. 8

    A catalytic converter which has been discolored may be due to an engine running rich, lean or had a previous severe misfire. Verifying the fuel trim percentages may be of assistance in determining if such a condition exists.

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