Testing The Oxygen Sensors (GM 4.3L, 5.0L, 5.7L)

Oxygen Sensor Codes Keep Coming Back

So you tested the oxygen sensors 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

There is one article that I recommend you take a look at that deals with testing a Lean condition. You can find this article here: Troubleshooting P0171 And P0174.

I've written quite a few 4.6L, 5.4L 'how to' tutorials that may help you troubleshoot the issues on your Ford car, pick up or SUV. You can find all at:

Here's a sample of the tutorials you'll find in this index:

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Chevrolet Vehicles:

  • Astro
    • 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
  • Blazer
    • 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
  • Blazer TrailBlazer
    • 1999, 2000, 2001

Chevrolet Vehicles:

  • C1500, C2500, C3500 Pick Up
    • 1996, 1997, 1998, 1999, 2000
  • Express Van 1500, 2500, 3500
    • 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007
  • G30 Van
    • 1996
  • K1500, K2500, K3500 Pick Up
    • 1996, 1997, 1998, 1999, 2000

Chevrolet Vehicles:

  • K1500, K2500 Suburban
    • 1996, 1997, 1998, 1999
  • P30 Van
    • 1996, 1997, 1998, 1999
  • S10 Blazer
    • 1994
  • S10 Pick Up
    • 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004

Chevrolet Vehicles:

  • Silverado 1500 Pick Up
    • 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2007
  • Tahoe
    • 1996, 1997, 1998, 1999, 2000

GMC Vehicles:

  • Sierra C1500, C2500, C3500
    • 1996, 1997, 1998, 1999, 2000

GMC Vehicles:

  • Suburban C1500, C2500
    • 1996, 1997, 1998, 1999
  • G3500 Van & Vandura
    • 1996
  • Jimmy & Envoy
    • 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
  • K1500, K2500, K3500 Sierra
    • 1996, 1997, 1998, 1999, 2000

GMC Vehicles:

  • P3500 Van
    • 1996, 1997, 1998, 1999
  • S15 Jimmy
    • 1994
  • Safari
    • 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005

GMC Vehicles:

  • Savana Van 1500, 2500, 3500
    • 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007
  • Sonoma
    • 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004

GMC Vehicles:

  • Yukon
    • 1996, 1997, 1998, 1999, 2000, 2001, 2002

Isuzu Vehicles:

  • Hombre
    • 1997, 1998, 1999, 2000

Oldsmobile Vehicles:

  • Bravada
    • 1996, 1997, 1998, 1999, 2000, 2001

Cadillac Vehicles:

  • Escalade
    • 1999, 2000