Codes P1131 - P1132 | Ford Explorer Forums - Serious Explorations

  • Register Today It's free!

Codes P1131 - P1132


Well-Known Member
September 19, 2015
Reaction score
Year, Model & Trim Level
1998 Explorer XLT
After an off road trip, and just after a hard muddy hill, with slipping wheels and some full gas throttle, I got the check engine light
Back in home, connect the scanner tool and read P1131 - P1132.

I know it means "Lack of Upstream Heated Oxygen Sensor Switch Sensor Indicates Rich Bank 1"
and "Lack of Upstream Heated Oxygen Sensor Switch Sensor Indicates Rich Bank 2"

The thing is, all my o2 sensors are new, and also the upper and lower intake orings

I performed again the fog machine test, and no leak in the intake, but have a leak in the mid of the EGR valve and a little bit in the black knob to the IAC valve

Is time for a new EGR? also IAC?

Join the Elite Explorers for $20 each year.
Elite Explorer members see no advertisements, no banner ads, no double underlined links,.
Add an avatar, upload photo attachments, and more!

Before you replace anything if you were muddin', I would pull apart the O2 sensor plug connections & clean them out you might not be getting a good connection.

Hi Mike

Thanks for your suggestion, but the mud really was no so bad and it didn't touch the o2 sensors or it connectors..

Today, I perform a new IAC clean, more intensive than the time before.

The take apart the IAC black knob, and I cleaned this area too... it is loose and do not seal the air pass... it is normal?

Now, the idle hesitate almost gone.

I bought a EGR from a junkyard, tomorrow i'll install it and will connect the truck to an scanner tool to check the fuel trims


Yes the knob/cover on the side should be loose so air can flow around it, but there should be two fiber filter pads inside that fit good to filter the air.

Some of your information doesn't make sense to me. You report P1131 as Rich Bank 1 and P1132 as Rich Bank 2, while I'm seeing P1131 as lean bank 1 and P1132 as Rich Bank 1.

I would suspect that the corresponding bank 1 O2 sensor connector was contaminated and making intermittent contact, that it was causing the system to run lean, ECU was compensating, then with momentary contact again the sensor feedback indicated rich. I just don't see a vac leak toggling back and forth between lean and rich, being as likely as the electrical connection.

Maybe the connector has dried out. I'd clear the codes and see if they come back.

Which connector color is the bank 1 sensor? green one?