Shuts off at idle/stop, code P0131

Tiny
PANCHO529
  • MEMBER
  • 1996 PONTIAC GRAND PRIX
  • 3.1L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 300,000 MILES
Good morning,

I have the car listed above that shuts off at idle or low RPM (such
as coming to a stop, reversing, stop signs/stop lights, etc). It will try and
correct itself jumping between 500 and 1,000 RPM's before it loses power. It
will turn back on immediately. It runs at highway speeds just fine and I don't
notice any issues accelerating. It also seems to be worse in the summer time
when it's warmer. The service engine soon light comes on and I pulled a
code (P0131 oxygen sensor circuit low voltage bank 1 sensor 1). I feel like
it's not getting as good of mileage as it should be and I feel like the exhaust
smells more than it should.

I've done some research and it seems that it could be a bad oxygen sensor,
wiring harness, dirty throttle body, dirty mass airflow sensor, bad mass
airflow sensor, idle air control valve, or crankshaft position sensor among
other things. My father-in-law is set on it being the O2 sensor, but I don't
want to just throw money at parts, but it's also going to cost me $120 to have
it diagnosed. Any thoughts? I know it wouldn't be a bad idea to replace many
of the parts as this car has 300,000 miles on it and an engine that has 150,000
miles. My father-in-law said he has never replaced the O2 sensor.

Side note. I found a random cord unplugged that sits behind the spark
plugs and have no clue where it connects. I'm not sure if this is part of the
issue or not. Here is a picture of it.

Thanks!
Tim
Tuesday, December 31st, 2019 AT 7:01 AM

5 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,747 POSTS
Hi,

The sensor is before the catalytic converter shortly after the exhaust manifold. I attached a picture of its location.

Now, low voltage (which is what this code indicates) can often be the result of corrosion or wiring damage at the connector. So, I would suggest checking that first.

To remove the sensor requires a special type of socket that allows the wiring to be undamaged. Otherwise, you will be trying to remove and install it using an open end wrench. The sensors are usually really tight from corrosion, so tell him to take his time. . All that's involved is unscrewing it and installing the new one (of course you need to disconnect the wiring)

As far as the picture you sent, can you get a closer pic of it? I can't tell what I'm seeing.

Let me know if you have questions or need help. Also, if you know of any other codes that weren't mentioned let me know.

One last thing, I question if the sensor is causing the stall issue. However, there is a problem, so lets get that fixed first and see if it remedies the stalling.

Take care.
Joe
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Wednesday, January 1st, 2020 AT 12:11 AM
Tiny
PANCHO529
  • MEMBER
  • 3 POSTS
Thanks for the response Joe. I talked to my father-in-law about the cord and he said it doesn't go to anything and has never been plugged in. I didn't notice any corrosion or damage to the wires. I'm going to replace the O2 sensor today or tomorrow and will update (my father in law has the socket required).
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Friday, January 3rd, 2020 AT 6:28 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,747 POSTS
Happy to help. Listen, if the sensor doesn't take care of the problem, often times an idle issue can be related to a vacuum leak or idle air control valve, so let me know. If by any chance you have access to a live data scanner, have your father in law to tell you what the short term fuel trims are. I can tell a lot by that.

Take care and let me know how things work out for you. Also, feel free to let me know if you need help or have questions.

Take care,
JOe
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Friday, January 3rd, 2020 AT 10:06 PM
Tiny
PANCHO529
  • MEMBER
  • 3 POSTS
I got the O2 sensor replaced today and it seems to be running well. I didn't notice any stalling issues at a stop once warmed up and my MPG went from 20 on average to 30. I'll update if anything changes.
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Saturday, January 4th, 2020 AT 10:06 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,747 POSTS
Glad to hear it's fixed. Let me know if anything changes or if you have questions in the future.

Take care,
Joe
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Saturday, January 4th, 2020 AT 6:34 PM

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