Help with P1311 code.

98gtr · Dec 11, 2006

My CEL came on a few weeks ago and is giving out this code. I don't understand what this means. I looked it up on the web and I'm getting opinions ranging from bad front 02 sensor to faulty MAF sensor, bad fuel pump, dirty injectors, etc. Can anybody help me out with this? My car idles normal except for slight seconds everynow and then. It seems like it wants to hesitate when its wet or raining sometimes nothing too bad though and doesnt quite have the take off speed at low rpms.

jstreet0204 · Dec 11, 2006

You sure that is the code? I'm not finding a DTC in my references using 1311.

98gtr · Dec 11, 2006

jstreet0204 said:
You sure that is the code? I'm not finding a DTC in my references using 1311.

Sorry about that, I meant P1131.

jstreet0204 · Dec 11, 2006

If it is driving bad when it rains like that, it is more than likely the o2 sensor. It would be the front passenger side o2. You can test it to make sure by swapping the two front o2 sensors. If the code follows the o2 then the o2 is bad. If it doesn't follow the o2 I'd start checking injectors. I personally just go ahead and replace it if it is fairly old.

JimC · Dec 11, 2006

P1131 - Lack of HO2S - 11 Switch, Sensor Indicates Lean

A HEGO sensor indicating lean at the end of a test is trying to correct for an over rich condition. The test fails when the fuel control system no longer detects switching for a calibrated amount of time.

Causes:
http://www.bullittarchive.com/WebHelp/help/mustangspecs/2001_Mustang_Specifications.htm

Mike97gt · Dec 11, 2006

P1131 - Lack of HO2S-11 Switch, Sensor Indicates Lean

first thing you need to do is read the long term + short term fuel trims for both banks and get the total fuel trims.

If you see something like

Longterm1.. 20 % + shortterm 1.. 10 percent then bank one has a total fuel trim of + 30 percent

then what you want to do is compare the total fuel trim on bank one to the total fuel trim on bank 2..

If bank 2 is normal ( total fuel trim under 12 percent either positive or negitive) then your concern could be a misfire, exhaust leak before the sensor or a bad sensor itself.

If bank 2 has a high total trim but has not set a code then I would lean more towards a bad MAF or vacumm leak.

98gtr · Dec 11, 2006

jstreet0204 said:
If it is driving bad when it rains like that, it is more than likely the o2 sensor. It would be the front passenger side o2. You can test it to make sure by swapping the two front o2 sensors. If the code follows the o2 then the o2 is bad. If it doesn't follow the o2 I'd start checking injectors. I personally just go ahead and replace it if it is fairly old.

Can you get to it from under the hood or do you have to jack the car up?

jstreet0204 · Dec 11, 2006

98gtr said:
Can you get to it from under the hood or do you have to jack the car up?

I have to get under the car to get them.

Mike97gt · Dec 11, 2006

it's most likely the sensor itself.. as Jstreet said I would just replace that sensor.

02s11 is the top 02 sensor on the passenger side right near where the mid pipe connects to the exhaust manifold.

If you have access to a real scan tool then you can look at live data and look at the stuff I pointed out.

Help with P1311 code.

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