P1131 - FAULT CODE - OBD2

P1131 Code failures by brands

P1131 FORD, LINCOLN, MAZDA, MERCURY: NO SWITCH HO2S - SENSOR INDICATES TILT.

P1131 HYUNDAI: ADJUSTING THE INJECTION QUANTITY

Description of DTC code P1131

The Oxygen Sensor (O2) gives the PCM (Powertrain Control Module) information to determine whether the engine is running rich or lean. The sensor referred to by code P1131 is located before the catalytic converter so that it knows how rich or lean the engine is running without the catalytic converter, affecting the composition of the exhaust gases.

To achieve its goal, O2 Sensors deliver a 0-1 signal to the PCM with 0.5 volts crossing point. When the sensor voltage is higher than 0.5, it is because the engine is running rich, and if it is below 0.5 volts, the engine is running poorly. This voltage should have variations between rich and poor so that the air/fuel mixture is as indicated.

When the diagnostic code P1131 OBDII is set, it is because the voltage sent back by the Oxygen Sensor is not changing within 0.5 volts.

Symptoms of fault code P1131

The Check Engine lamp lights up.
Decreased fuel efficiency.

Causes of OBD2 P1131

The reasons for the storage of fault code P1131 OBD2 are

The engine may have vacuum leaks.
One or more fuel injectors may be blocked or clogged.
Fuel pressure may be too low.
The Mass Airflow (MAF) sensor may be dirty or in poor condition.
Possibly the Oxygen Sensor is defective.

Possible solutions of the DTC code P1131

The steps to correct the DTC code P1131 OBDII are the following:

As a first step, it is necessary to consult the TSB (Technical Service Bulletins).
Verify that no other codes are stored, especially if they are related to the exhaust system. If these codes are present, you should perform the proper diagnosis before P1131.
After locating the Oxygen Sensor, check its connector and related wiring. If you discover common damage caused by high temperatures or friction, fix or replace as required.
Use a scanning tool to monitor the signal from the MAF sensor to the PCM. If you don't have access to a scanner, you can use a grounded voltmeter. Start the vehicle and monitor the MAF Sensor input, which as the engine speed increases, should be higher accordingly. Check the manufacturer's specifications for the voltage you should get, and if there is no match, replace the sensor.