: Help? Went to Auto Zone to run a code on my 99 F-150 4.6 because check engine light came on. Been running rough for several weeks. Was told that this code is a secret code put in by Ford. Can anyone tell me where to cross reference this code?

P1131 : insufficient switching control valve Semsor/Lean

Thanks

beenthere

 

I found this site pretty useful
www.obd-codes.com

 

Look at the site. Nice, I will try cleaning MAF before looking else where!

 

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.

Which basically means the upstream O2 sensor on bank one isn't switching

 

Does this meem I should replace the o2 sensor on the manifold or both of them before replacing the MAF.

 

I had the same code. I replaced the pasenger side upstream oxygen sensor and it has seemed to fix the problems

 

There is no secret in there. That's the language used by the computer to talk to us or whoever may be interested.

I had a similar problem with the upstream sensor in bank one but changed both of them because of high mileage (111K miles). As soon as I can I will be changing the downstream's, but not in a hurry since there is no trouble code now.