Oxygen Sensor Codes Keep Coming Back

So you tested the oxygen sensor and they tested good or you have already replace one or both and yet the PCM keeps accusing them as being bad (which also means that the check engine light is back on).

When this happens, it's usually due to either a Rich condition or Lean condition that's being caused by some other component on the engine.

What sucks about this, is that whatever is causing the Rich or Lean condition is not present all of the time (specially when you're conducting the tests). This happens quite a bit. The strategy here is to wait a few days for the condition (that's causing the O2 sensor issues) to get worse. When this occurs, you'll be able to test it and solve it.

More Test Articles

I've written quite a few 3.8L 'how to' tutorials that may help you troubleshoot the issues on your GM car, pick up or SUV. You can find the complete list here: GM 3.8L Index Of Articles.

Here's a sample of the GM 3.8L V6 articles you'll find:

  1. How To Diagnose Misfire Codes P0300-P0306 (GM 3.8L).
  2. How To Test The Fuel Injectors (GM 3.8L).
  3. How To Do An Engine Compression Test (GM 3.8L).
  4. How To Test The 3.8L GM Crank Sensor With A Multimeter.
  5. How To Test The Coil Packs (at: easyautodiagnostics.com.
  6. How To Test The Ignition Module (at: easyautodiagnostics.com).
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Buick Vehicles:
  • Century 3.1L, 3.3L
    • 1989, 1990, 1991, 1992, 1993, 1993, 1994, 1995, 1996
  • LeSabre 3.8L
    • 1988, 1989, 1990, 1991, 1992, 1993, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
Buick Vehicles:
  • Park Avenue (& Ultra) 3.8L
    • 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
  • Reatta 3.8L
    • 1988, 1989, 1990, 1991
Buick Vehicles:
  • Regal 3.8L
    • 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004
  • Riviera 3.8L
    • 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999
  • Skylark
    • 1988, 1989, 1990, 1991, 1992, 1993
Cadillac Vehicles:
  • Deville
    • 1996, 1997, 1998, 1999
  • ElDorado
    • 1996, 1997, 1998, 1999
  • Seville
    • 1996, 1997, 1998, 1999
Chevrolet Vehicles:
  • Camaro 3.8L
    • 1996, 1997, 1998, 1999, 2000, 2001, 2002
  • Impala 3.8L
    • 2000, 2001, 2002, 2003, 2004, 2005
  • Lumina 3.8L
    • 1998, 1999
  • Monte Carlo 3.8L
    • 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
Oldsmobile Vehicles:
  • Achieva 3.3L
    • 1992, 1993
  • Aurora 3.8L
    • 1996, 1997, 1998, 1999
  • Cutlass Calais (Ciera, Cruiser) 3.1L, 3.3L
    • 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996
  • Delta 88 (Royale Brougham)3.8L
    • 1989, 1990, 1991
Oldsmobile Vehicles:
  • Intrigue 3.8L
    • 1998, 1999
  • LSS 3.8L
    • 1996
  • 88 Royale 3.8L
    • 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999
  • LSS
    • 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999
Oldsmobile Vehicles:
  • 98 Regency 3.8L
    • 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996
  • Silhouette 3.8L
    • 1992, 1993, 1994, 1995
  • Toronado 3.8L
    • 1988, 1989, 1990, 1991, 1992
Pontiac Vehicles:
  • Bonneville 3.8L
    • 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
  • Firebird 3.8L
    • 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002
  • Grand Am 3.3L
    • 1992, 1993
Pontiac Vehicles:
  • Grand Prix 3.8L
    • 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005