The banner above is an advertisment - if it asks you to download software, please ignore.
Site News - 7/1: Members: Log In to See Fewer Ads! | 5/28: SAAB Evolutions/TSN T-Shirts $14
[General | Members | C900 | 9000 | NG900 & OG93 | 93 | 95 | NG95 | 99 | Sonett | Vintage Models | Clubs | Other Cars | FAQs | Gifts | Member Photo Galleries | Member Directory | Classifieds | Manuals | *Buddy Registry | *Mileage Registry | Polls | What's New | Raffle | Photo of the Month | Sponsors]

C900 Bulletin Board
1979-1993 & 94 Conv [Subscribe to Daily Digest]
(Search Author's Posts: e.g. Keyword:username)*Members Only

[Main C900 Bulletin Board | BBFAQ | Prev by Date | Next by Date | Post Followup ] Member Login / Signup - Members see fewer ads. - Latest Member Gallery Photos
Re: O2 Sensor Failure?
Like This Post: - Subscribe to Daily Digest for this Bulletin Board
Posted by Ari [Email] (#2847) [Profile/Gallery] (more from Ari) on Wed, 11 Aug 2004 07:54:55 Share Post by Email
In Reply to: O2 Sensor Failure?, Justin VanAbrahams [Profile/Gallery] , Tue, 10 Aug 2004 20:40:15
Alert me when someone posts in this thread:
Members do not see ads below this line. - Help Keep This Site Online - Signup

The heater is nice, but all it does is heat up the O2 sensor faster for emissions purposes. Once the O2 sensor hits 200 degrees, it starts working. With the heater, that's about 2 minutes. With a running engine, that's about 5 minutes. So always let the engine and O2 sensor warm up at least 5 minutes before taking measurements.

Checking the output of the O2 sensor with the sensor wire disconnected from the ECU doesn't work. The ECU will assume a bad O2, and set an assumed value. Depending on how the engine is running, that means the mixture can be all over the place. And the O2 sensor could be telling the truth.

I see two approaches - 1 - do your best to test the sensor. Or 2 - since you've already pulled it, just replace the damn thing. It may not fix it, but all you'll be out is $50 for an aftermarket replacement.

To test the O2 sensor, with the sensor wire connected to the ECU and the engine and sensor warm, use a voltmeter to measure the sensor wire to ground, the meter set to volts. You'll need to find a way to tap into that wire. At idle, ideally the voltage should be swinging back and forth from about 0.2 volts to about 0.9, about 1/second. A rich mixture is 0.9 volts; lean is 0.2.

I'll assume that the sensor is stuck hard over to one voltage. That would cause the CEL. If it's stuck on the rich side, pull a vacuum line off the intake manifold. Just don't pull the line going to the FPR. See if that causes the voltage to swing towards 0.2 If so, then the sensor is probably OK, and something else is causing a rich mixture. If the sensor is stuck on lean, pull the hose from the intake manifold to FPR off and PLUG IT. This will cause the FPR to increase fuel flow. See if the O2 sensor swings rich. If so, the sensor is probably OK, and you've got a vacuum leak somewhere.

The difficulty in troubleshooting a closed loop system is that things try and compensate. So if there is a big vaccum leak, you'll run lean. The system will try and compensate, but can only compensate so much. If the O2 sensor is still reporting lean, the ECU declares it bad.



posted by 192.249....
Posts in this Thread:
Alert me when someone posts in this thread:
Members do not see ads below this line. - Help Keep This Site Online - Signup
Post a Followup

No Site Registration is Required to Post - Site Membership is optional (Member Features List), but helps to keep the site online
for all Saabers. If the site helps you, please consider helping the site by becoming a member.

Name: Member Login / Signup - Members see fewer ads. - Latest Member Gallery Photos
E-Mail: (Optional)
Re-Enter E-Mail: (Confidential & Secure - Not revealed to other users!)
Note: Please check your spam folder for BB responses.

Subject:

Posting rules are simple - No for sale/wanted ads may be posted here - use the site classifieds.
You may not cross-post your message to multiple BBs.
Not permitted: political/religious topics and being disrespectful (personal attacks, insults, etc...).
 Site Members do not see any red text, inline ad links, bottom of page anchor ads, box ads, or anti-spam check.

Message: (please no for sale/wanted classifieds - post those in the Saabnet.com Classifieds)
Links are now automatically made active, no need for any special code (or use the Option Link field below) - don't put links in () or end with a '.'
To add inline images to your post, use [img]http://www.domain.com/img.jpg[endimg] (or use the Optional Image Link field below).

Links are now automatically made active, no need for any special code (or use the Option Link field below) - don't put links in () or end with a '.'
To add inline images to your post above, use [img]http://www.domain.com/img.jpg[endimg] (or use the Optional Image Link field below).
Optional Link: (e.g. http://www.saabnet.com/)
Link Title: (Optional)
Optional Photo/Image Link: (e.g. http://www.saabnet.com/img.jpg)
Photo/Image to Upload: (Please be patient while file uploads)



StateOfNine.com
SaabClub.com
Jak Stoll Performance
M Car Covers
Ad Available

The content on this site may not be republished without permission. Copyright © 1988-2024 - The Saab Network - saabnet.com.
For usage guidelines, see the Mission & Privacy Notice.
[Contact | Site Map | Saabnet.com on Facebook | Saabnet.com on Twitter | Shop Amazon via TSN | Site Donations]

Random Saabnet.com Member Gallery Photos (Click Image)
This is a moderated bulletin board - Posting is a privilege, not a right. Unsolicited commercial postings are not allowed (no spam). Please, no For Sale or Wanted postings, SERIOUSLY. Classifieds are to be listed in The Saab Network Classifieds pages. This is a problem solving forum for over 250,000 Saab owners, so expect to see problems discussed here even though our cars are generally very reliable. This is not an anything goes type of forum. Saabnet.com has been a moderated forum since 1988. For usage guidelines, see the Saabnet.com Mission and Purpose Page. Please remember that you are not anonymous. Site Contact | Site Donations | Other Sites by SP - Poverty2Prosperity.org | Run Club Menlo Park | ScreenBot


Site Members do not see red text instructions, bottom of the page anchor ads, or box ads.
Click here to see all the Site Membership Benefits!