There are several reasons your car's computer has thrown a heated oxygen sensor (HO2S) P1131 code, indicating too much fuel going into the combustion chambers. In most cases, you can use a common check to correct the problem by cleaning or replacing one or more items. HO2 sensors take a lot of use over the years and you might have to replace it. Still, in a few minutes, you can often restore your engine performance right in your own driveway and save on repair costs.
Inspect the vacuum hoses in your vehicle by tracing each hose with your hand, looking for holes, tears, loose or disconnected ends. A leaking vacuum hose can introduce too much oxygen and cause a P1131 code. Replace any damaged vacuum hose.2
Check the valve and hose on the positive crankcase ventilation (PCV) system. This is the small cylinder or small L-shaped valve, about the size of a spark plug or smaller, connected to the intake manifold and the valve cover on top of your engine through a rubber hose. You can manually disconnect the valve and shake it. If you can hear it rattling, the valve is in good shape. Otherwise, clean it or replace it. If the PCV hose is blocked with gunk or torn, clean it or replace it.3
Locate the primary oxygen sensor between the exhaust manifold and the catalytic converter, a box like component in the exhaust (header) pipe connected to the exhaust manifold. The sensor is about the size of a spark plug and threads on the exhaust manifold or header pipe connected to the manifold, depending on your vehicle. You will recognize it by the three electrical wires coming out of the sensor's tail.4
Raise the front of the vehicle using a floor jack and support it on jack stands, if you need access to the sensor from under the vehicle. Block both rear wheels with two pieces of 2-inch by 4-inch wood blocks. Apply the parking brakes.5
Unplug the sensor's electrical connector and unthread the sensor from the exhaust manifold or header pipe using an oxygen sensor socket and ratchet.6
Apply anti-seize compound to the threads of the new sensor, if the new unit does not have the compound on the threads already.7
Start the sensor on its mounting boss by hand to prevent thread damage. Tighten the sensor with the oxygen sensor and ratchet.8
Plug in the sensor's electrical connector.9
Lower your vehicle off the jack stands using the floor jack, if you had to raise it, and remove the wood blocks.