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Home >> Chevrolet >> 2001 >> Venture Base, Van Passenger >> Repair and Diagnosis >> External Pages >> Different car >> Section 77 (Engine Controls - Self-Diagnostics - 3.0L) >> Diagnostic Tests >> DTC P0421: Warm-Up Catalyst - Low Efficiency - Bank 1 >> Diagnostic Aids

Diagnostic Aids

WARNING: This page is about a different car, the 2002 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.

Make sure no exhaust leaks exist between the HO2S bank 1 sensor 1 and 18" after the HO2S bank 1 sensor 2. An exhaust leak in that area will cause false HO2S bank 1 sensor 2 readings and may set DTC P0421. Repair a leak if one exists and drive vehicle to verify the P0421 diagnostic has run and passed. Follow the enable conditions under DTC parameters.

A misfiring cylinder(s) on bank 1 pushing raw fuel out the exhaust port will damage the pre-converter over time. Verify that no current or history misfire counts exist in any failure record. Repair a currently misfiring cylinder(s) if one exists.

Replace the bank 1 pre-catalytic converter. Bank 1 (cylinders 1, 3, 5) are closest to front of dash.

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