Contour Enthusiasts Group Archives Forums General Troubleshooting Code P1131

Does anyone know what this code means and how to fix it? I just got back from Autozone and thats the code they pulled. Thanks.

yes i had this code pop up so many times. It an oxygen sensor, that kept on making my CEL pop on. I have a computer diagnostic tool though, so it's easier and free for me . I believe that it's sensor 1 in bank 1. I just gave mine some time, because this is a common error, and my CEL went away by itself after a week or two, and it hasn't come back on in over a month.

Mine must really be going bad then. It will come on for a day or so then go back off for a day. Oddly enough I have an O2 sensor for the car sitting right in front of me. Are you sure its sensor 1 bank 1? Which one is that?

I am now sure that it is. I went to diagnosticdialog.com and entered it, and this is what came up.

Diagnostic Trouble Code Description
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Trouble Code: P1131
Vehicle Qualification: Ford Contour
Description: Lack of HO2S Bank 1 Sensor 1 Switches - Sensor at Lean Limit

I don't have a clue though, as to where it is or how to replace it, i never did.

So it isn't even necessarily that the O2 sensor is bad...

Nope not necessarily. How long has your been on, or coming on and off?

I had the [censored] C&L MAF on for a while, but took it off because I only had it there while I couldn't find the stock one. Then I switched back and now it comes on and off pretty regularly. It's usually on more than it's off, but I find when I get lower on gas it usually comes on then when I fill up it'll go away.

So I found this online:


P1131 Lack Of HO2S1 Switches, Lean (Bank 1, Sensor 1)
P1137 Lack Of HO2S1 Switches, Lean (Bank 1, Sensor 2)
These codes usually do not indicate a problem with the O2 sensor. Rather, the O2 sensor is correcting rich due to an overly lean air/fuel ratio. Check Base Engine Idle, EGR, Fuel System and Air Induction System.
Bank 1 refers to the bank of cylinders containing Cylinder #1.
Sensor 1 refers to the O2 sensor closest to the exhaust manifold.
Sensor 2 refers the O2 sensor downstream of the catalytic converter.


So what should I do if thats saying it doesn't mean the O2 sensor has gone bad? I have a filter, but the MAF is stock. I do have a different tube connecting the MAF to the TB though. Could that be it? Or just the filter? Should I just get a chip or Apexi SAFC? haha

If the oxygen sensors have been in the vehicle for over 60K (up to 100K, which is the recommended replacement interval for OBD-II cars), they should probably be changed anyway.

Especially given how "fragile" the pre-cats are. Not that I'm suggesting that a worn out, sluggish oxygen sensor could cause a pre-cat to fail....I'll leave that to Bosch[1], but it is rather interesting, isn't it, that I got a code P1151 (bank 2 oxygen sensor not switching/lean limit), drove around with it for about 300 miles, replaced the sensor, and shortly after I replaced the bank 1 oxygen sensor, I got a P0430 (bank 2 catalyst efficiency below threshold).[2]

Then again, it's also rather suspicious that I made the P0430 code "go away" by cleaning the throttle body with the engine running[3], and then passed the emissions check with the lowest readings the car has ever gotten. I also replaced the bank 1 oxygen sensor, figuring that if the bank 2 sensor had crapped out, bank 1 can't be far behind.

[1] Bosch states that a faulty oxygen sensor can cause catalyst failure. Maybe they're overstating the case to sell a few more, but my bank 1 sensor was really wacked. Clear the P1151 code and it'd come back within two drive cycles.

[2] The catalyst monitor does not run if there are any pending or active oxygen sensor codes.

[3] See my post about this here

By the way it's been my experience, at least with the V6 Contour, that oxygen sensor "lack of switch/lean" codes are caused by a bad oxygen sensor.

I've gotten the code 4 times among two different V6 Contours, and each time, yes, it was the oxygen sensor.

Now if BOTH oxygen sensors were reading lean I might suspect some other problem like an intake manifold leak.