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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 335 (Engine Controls - Self-Diagnostics - 3.0L) >> Diagnostic Tests >> DTC P0421 Or P0431: Warm-Up Catalyst - Below Threshold >> Diagnostic Aids

Diagnostic Aids

WARNING: This page is about a different car, the 2003 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.

The catalyst test may abort due to a change in the engine load. Allow the engine to return to stabilized idle. An automatic transmission must remain in Drive. A manual transmission is shifted to Neutral. Do not touch the accelerator pedal, steering wheel, or HVAC controls while a catalyst test is in progress.

Certain conditions may cause a catalytic converter to degrade. These conditions may include the following: An engine misfire, high engine oil or high coolant consumption, retarded spark timing, weak spark, lean fuel mixture, rich fuel mixture or damaged oxygen sensor wiring harness.

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