How common is it for post-cat O2 sensors to affect the A/F mix? I used to believe only the pre-cat sensor(s) had to do with A/F mix and the post-cat sensor(s) were only for monitoring exhaust. It has come to my attention that some engines will develop drivability problems if a post-cat O2 sensor malfunctions. Is this something new or something that simply has escaped my attention until now?
Post-O2 sensor question
- Thread starter vavavroom
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Originally Posted by vavavroom
It has come to my attention that some engines will develop drivability problems if a post-cat O2 sensor malfunctions.
????
Where did you hear that?
I have never, ever heard that to be true.
It is nearly IMPOSSIBLE to get any accurate A/F reading after a properly functioning cat!
It has come to my attention that some engines will develop drivability problems if a post-cat O2 sensor malfunctions.
????
Where did you hear that?
I have never, ever heard that to be true.
It is nearly IMPOSSIBLE to get any accurate A/F reading after a properly functioning cat!
Originally Posted by vavavroom
The specific claim was that the ECM on some cars (CA emission systems) uses the downstream O2 sensor for fine-tuning the A/F mix until the correct (within spec) amount of oxygen is measured at the downstream O2 sensor.
Yes, your right
At the 2:50 mark, it's mentioned
I've seen several people get burned by trying the old anti fouler/spacer trick to hide a P0420 catalyst efficiency code
On some cars (like the mentioned vintage Mopar), that'll do more harm then good.
The specific claim was that the ECM on some cars (CA emission systems) uses the downstream O2 sensor for fine-tuning the A/F mix until the correct (within spec) amount of oxygen is measured at the downstream O2 sensor.
Yes, your right
At the 2:50 mark, it's mentioned
I've seen several people get burned by trying the old anti fouler/spacer trick to hide a P0420 catalyst efficiency code
On some cars (like the mentioned vintage Mopar), that'll do more harm then good.
Originally Posted by vavavroom
The specific claim was that the ECM on some cars (CA emission systems) uses the downstream O2 sensor for fine-tuning the A/F mix until the correct (within spec) amount of oxygen is measured at the downstream O2 sensor.
This is correct. It just depends on the mfgs ECU program.
The specific claim was that the ECM on some cars (CA emission systems) uses the downstream O2 sensor for fine-tuning the A/F mix until the correct (within spec) amount of oxygen is measured at the downstream O2 sensor.
This is correct. It just depends on the mfgs ECU program.
Last edited:
Originally Posted by vavavroom
The specific claim was that the ECM on some cars (CA emission systems) uses the downstream O2 sensor for fine-tuning the A/F mix until the correct (within spec) amount of oxygen is measured at the downstream O2 sensor.
True, not only CA either my M35 does this.
The specific claim was that the ECM on some cars (CA emission systems) uses the downstream O2 sensor for fine-tuning the A/F mix until the correct (within spec) amount of oxygen is measured at the downstream O2 sensor.
True, not only CA either my M35 does this.
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