I have a 1999 F150 XLT with a 4.6 litre engine. The service engine light came on and a garage said the code was P1131. They think it might be a oxygen sensor, but I had one replaced a year or so ago. It has about 90,000 miles. The light comes on for a few days and then went off, but just came back on. Any opinions from the experts here? Anything else I should do than replace the oxygen sensor. Is it easy to do? How?

Thanks!

 

It is either bad or has a bad connection at the connector. You have 4 O2 sensors, are you sure that that is the one that you had replaced?

 

Not sure which one was replaced. Other research I have done so far indcates it might be the one on the passenger side close to the exhaust manifold. Other research said to clean the MAS(?) on the air filter unit to see if it causes the light to go out. I hope to resolve it this weekend.
Thanks!

 

P1131 Ford, Lack of HO2S bank 1 sensor 1, Sensor Indicates Lean
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Bad sensor, sucking air or bad connection ?

 

Any ides of where and how to start to try and figure it out?

 

Passenger side nearest the manifold is correct.
Check the plug for corrosion. Is sounds like it may be failing. usually a vacuum leak will cause P0171 and P0174.