Hey all!

Bringing this back up here for a sec...

1996 Blazer LT
-Issue: Rough idle, sluggish
-Pulled codes P0140 and P0146

From what I read above this has to do with the 3 or maybe 4 O2 sensors before the cat? And there's no way to find out which ones are malfunctioning unless GM runs a graph test?

It has a brand new cat on it and the rough idle happens most days but not all time.

Advice from the pros here would be appreciated!

Thanks!

*Edit by swartlkk*
*Moved from THIS THREAD* To keep things more up to date and not to drag up very old threads.

 

Actually, I do not know how or where you were lead to believe that there is no way to tell which O2 sensor is at fault. Your system has 4 O2 sensors. One on each exhaust tube between the manifolds and the Y in the y-pipe. These are your upstream sensors (B1S1 - driver side & B2S1 - passenger side). Then B1S2 is located between the Y in the y-pipe and the catalytic converter (96-97 only). B1S3 is after the catalytic converter.

Now, about your codes:
P0140 - HO2S Circuit Insufficient Activity Bank 1 Sensor 2 - click on the link for a description and possible causes.

P0146 - HO2S Circuit Insufficient Activity Bank 1 Sensor 3 - this code is very similar and has the same diagnostic procedures as P0140.

These two O2 sensors have no bearing on fuel delivery to the engine. They are catalyst monitoring sensors only.

Were the codes present prior to changing the catalytic converter? I would suspect wiring damage that is affecting the operation of these sensors. If a ground has gone bad, it could affect the other O2 sensors as well, causing the rough running that you are experiencing, but this would typically be accompanied by codes for those sensors as well.

Hope this helps!d

 

Thanks swartlkk!

Apologies for bring the old post back from the dead. I'm used to forums replying with "do a search" etc...

I do not know if the codes were there before the cat was replaced as I just bought it a month ago and the previous owner replaced the cat and it ran fine.

I'll check the wiring/connections. Could be water or coroded as it's full on winter here with tonnes of salt. If no go then I'll bring it to the dealer. I'll reply with the outcome/fix.