Rick's Free Auto Repair Advice

P0131

Fix code P0131

Oxygen Sensor Circuit Low Voltage (Bank 1 Sensor 1). This sensor is located on the engine bank that houses #1 cylinder and is located BEFORE the catalytic converter

The PCM sends a reference voltage (usually 5-volts) to the variable resistor in the oxygen sensor and looks for a return voltage. Once the sensor is heated up, the PCM expects to see a varying voltage. If the PCM sees a constant low voltage, it will set a trouble code P0131.

Most common causes are: vacuum leak that’s allowing too much unmetered air into the combustion chamber and causing lean misfires, bad oxygen sensor, poor connection either at PCM or O2 sensor.

oxygen sensor, P0130

oxygen sensor wire colors

TEST: Very difficult to test without either scope or scan tool. The most effective way to determine if you have a vacuum leak is to examine the fuel trim reading on a scan tool. If you have a vacuum leak and the sensor detects a continuous lean exhaust condition, the PCM will add fuel to compensate. Fuel trim should be as low as possible, but never approaching 25%. That would indicate a vacuum leak.

To learn how to replace an oxygen sensor, click here

 

© 2012 Rick Muscoplat

Posted on by Rick Muscoplat


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