What does P0140 mean and what can I do to fix it?

 

It is dealing with O2 Sensor. You can replace it, but they are sometimes pricey. That's all I got, anyone else??

 

P0140 - O2 Sensor Circuit Not Activity Detected (Bank 1 Sensor 2)

You'd have to look at your exhaust, but if you have 4 O2 sensors, this is the pre-cat sensor. If it has 3 sensors, then this would be the post-cat sensor. You should have B1S1 on the driver's side downtube of the 'y' pipe. B2S1 will be right before the two downtubes connect in the 'y' pipe. And again, if you have 4 sensors, then B1S2 will be right before the catalytic converter and B1S3 will be after the catalytic converter. If you only have 3 sensors, then B1S2 will be after the catalytic converter.

For me to diagnose further, I would need to hook it up to my scantool. I really cannot recommend to just replace the sensor without seeing a scan log, but that is up to you. Many times, the sensor is bad.

 

What kind of symptoms does something like this cause?

 

Should not cause any drivability concerns. B1S2 and B1S3 are for emissions monitoring only. I would first inspect all connections and grounds to make sure that everything is on the up and up. Try cleaning the B1S2 sensor connector with electronic parts cleaner, allowing it to thoroughly dry before hooking it back up. DO NOT use dielectric grease on O2 sensor connectors.

If a scan tool is available that can graph the sensor data, take a look for anything out of the ordinary (like drop outs, or other abnormal activity). If a scanner is not available, well... Either take it to a shop to have it diagnosed (most often they'll just replace the sensor without actually diagnosing it further than reading the codes) or replace it yourself. I would first have the code cleared and see if it comes back. Could have just been a fluke.

Anyway, if you do decide to replace the sensor, spend the extra coin for either an AC Delco or NGK direct replacement O2 sensor (I now believe that NGK is the OEM for AC Delco O2 sensors - atleast some of the models including ours).

 

I did clear the code with the OBDII Scanner and it did comeback, in fact I tried clearing it a couple of times and it keeps coming back. I will try cleaning the sensor and connections but if that doesn't work I'll probably just replace it. One other thing, I know you say it doesn't cause any drivability concerns but does it make a difference in fuel mileage?

 

No, only B1S1 & B2S1 have an impact on IPW (injector pulse width) as far as O2 sensors go. B1S2 & B1S3 (if so equiped) are for OBD2 catalyst monitoring purposes only.

 

good to know thanks. One other thing could any of this mean that catalytic converter is clogged? My truck sounds kind of loud when I start it up but its not loud after it gets going at about 30mph, also it feels kind of sluggish pulling away.

 

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!

 

When something is this old, it should remain dead and a new thread started. You can link back to an older thread such as this... I will repost your problem in a new thread.