Well, obviously, the O2 sensor senses O2. What it's measuring when it looks at the oxygen remaining in your exhaust is really how rich or lean your combustion mixture is.

The O2 sensor sends a signal to the fuel controller to increase or decrease the dwell (spray) time of the injectors. You may notice how a Saab at idle will "hunt" up and down slightly in RPM. It's really oscillating between a slightly rich and slightly lean mixture all the time. The O2 sensor sees a rich mixture, the fuel controller responds by leaning it (less injector spray time), then the sensor reports it's now too lean, and the controller responds the other way. Over and over, repeatedly. The O2 sensor is the "nose" which allows the car's "brain" to sniff the exhaust and adjust the mixture to be juuuuust right.

Typically if the O2 sensor goes bad, you'll get a Check Engine indication of some sort. Mine would illuminate briefly when I shifted. My Saab manual recommended replacing the sensor every 30,000 miles, but every mechanic I ever talked to said not to do that. I didn't argue, as the dealer wanted $300 to replace it. As it was, my original sensor lasted over 150,000 miles and over 13 years. And of course, the wonderful people here on the SaabNet informed me I could get a generic Bosch replacement for around $40, so I did.

Hope this answers your question, L!
- = M = -

• Who has taken out o2 sensor?..., cutic, Wed, 10 Jan 2001 09:20:39
  • thanks everyone n/m, cutic, Thu, 11 Jan 2001 09:15:15
  • How quickly they forget..., Monster, Wed, 10 Jan 2001 15:58:52
    • stuck under the dashboard eh, where can I read that? n/m, anothermike, Wed, 10 Jan 2001 22:53:41
      • Scrolled off the list..., Monster, Thu, 11 Jan 2001 08:27:12
    • O2 Sensor Woes and My Love/Hate Saab Relationship, Monster, Wed, 10 Jan 2001 16:02:23
      • O2 Sensor Woes II -- The Sequel, Monster, Wed, 10 Jan 2001 16:06:48
        • Re: O2 Sensor Woes II -- The Sequel, Matt, Wed, 10 Jan 2001 23:38:41
          • Sometimes the Norse gods smile on you...., Monster, Thu, 11 Jan 2001 08:04:19
  • Just what does the o2 sensor do? n\m, LMS, Wed, 10 Jan 2001 12:49:35
    • senses exhaust gas oxygen..., Monster, Wed, 10 Jan 2001 22:38:51 <-- Viewing This Message
      • Re: senses exhaust gas oxygen...To monster, LMS, Thu, 11 Jan 2001 14:10:38
        • Yer welcome! :> n/m, Monster, Fri, 12 Jan 2001 00:39:43
        • Re: senses exhaust gas oxygen...To monster, M, Fri, 12 Jan 2001 00:38:55
  • Re: Who has taken out o2 sensor?..., Rob T, Wed, 10 Jan 2001 11:29:20
  • Answer: Grind the socket so it fits, JohnK, Wed, 10 Jan 2001 10:30:04
  • 87 900T?, JohnB, Wed, 10 Jan 2001 10:17:08
    • But you gotta twist and hold your mouth just so!! n/m, Texron, Wed, 10 Jan 2001 10:21:13
      • Yeah, but I keep biting my tongue and liking the blood., JohnB, Wed, 10 Jan 2001 15:23:45
  • Re: Who has taken out o2 sensor?..., Alain(Luxembourg), Wed, 10 Jan 2001 09:54:47
  • The easiest way that I've seen, Jeff Cunningham, Wed, 10 Jan 2001 09:39:58
    • BINGO! Jeff is correct., Paul Bob, Sun, 13 Aug 2006 20:26:45
      • Re: BINGO! Jeff is correct., oldsaab, Sun, 13 Aug 2006 22:55:51

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