Cause of BOTH P1131 and P1132???
 

Hi,

I am trying to determine the most likely cause of getting both the P1131 and P1132 (HO2S not switching - LEAN and HO2S not switching -- RICH) error codes on my '97 Expedition. Seems strange that the problem could be both causing lean AND rich conditions. It also seems unlikely that the cause is a dirty MAF, even though I'm running a K&N air filter, since the problem is occuring only on one side. Is it as simple as the upper HO2S sensor gone bad?

Thanks!

If the code is "H02S11 not switching, indicates rich and lean" or something of that sort then, I would guess that you have a bad 02 sensor. If it is the one on the passanger side, check for the evaporator drain tube leaking onto the 02 sensor. I know there was a TSB for this, but I am not sure what engine(4.6, 5,4) and what DTC's codes you will recieve.

Change the O2 sensor, I just went through this for two months. I tracked down everything that could cause these codes. In the end it was just a bad O2. I currently have 84,000 miles on a 1998 F-150. If you are getting up there in milage like 60,000 or more miles then the O2 sensors will start failing.

Good Luck