P0157 - 02 LOW VOLTAGE CIRCUIT SENSOR (BANK 2 SENSOR 2)

DTC code P0157 refers to a failure in the O2 sensor (Oxygen sensor) located in bank 2 just behind the catalytic converter (TWC).

The Three-Way Catalyst (TWC) is used to help control exhaust emissions, i.e. you can clean the exhaust if you wish. The PCM (Powertrain Control Module) uses the signal from the number 2 oxygen sensor to monitor the effectiveness of the catalyst. If the Powertrain Control Module detects no difference in exhaust quality between the oxygen sensors, it indicates that the catalyst is not working properly.

It should be noted that this diagnostic code does not mean that the catalytic converter is defective because this tool cannot be broken frequently.

Basically, this code indicates the voltage of the signal produced by the oxygen sensor in bank two is below, which is considered normal for this sensor.

The O2 has four wires; one of them provides a 5-volt reference signal, one for the ground, one for the power circuit, and one ground circuit for the oxygen sensor heating element. When the oxygen content changes, the resistance in the sensor signal circuit also changes. This varying resistance affects the 5 volts in the reference signal circuit. The power train control module (PCM) monitors this signal. Thus, it determines whether the catalyst is operating correctly. If the PCM concludes that the signal voltage of the oxygen sensor two does not operate to the set degree, the fault code P0157 OBD2 is set.

• The Check Engine Light on the dashboard lights up.
• Engine performance problems.

The diagnostic code P0157 OBD II means that one or more of the following problems have occurred:

• Air leak in the exhaust pipe just in front of the oxygen sensor.
• The connector of the oxygen (O2) sensor may be defective.
• The signal circuit of the oxygen sensor may be shorted to the ground.
• The oxygen sensor may be contaminated with fuel or even coolant
• The oxygen sensor may be defective.

With code P0157 you can do the following:

• The first thing you should do is check for air leaks in the manifold and the exhaust. In case you find some faults, repair them.
• With the engine off, unplug the oxygen sensor connector, inspect it for corruption or wear, and repair it if you find any inconsistencies. Check all circuit wires corresponding to the oxygen sensor. Repair or replace if any of these are defective.
• Verify that battery voltage and ground are present for the oxygen sensor heating element. Remember that the oxygen sensor depends on the heating element to start working faster. If the heating element is defective, the voltage that will be fixed can set this code, if the heating element is bad, you must replace the sensor.