P0156 - 02 SENSOR CIRCUIT MALFUNCTION (BANK 2 SENSOR 2)

The oxygen sensors measure the oxygen content in the exhaust, then, they send that data to the PCM (Powertrain Control Module). The PCM uses the information provided by the sensors and regulates the fuel injector pulse.

The diagnostic code P0156 OBD2 refers to the Oxygen Sensor number 2 which is located in bank number 2. This sensor has four wires. The PCM provides a ground circuit plus a voltage circuit with a 0.5-volt reference. The other two wires are for the oxygen sensor heating element, one for the battery voltage, and the other for the ground circuit. The heating element helps the oxygen sensor heat up faster, and thus a closed loop can be made in less time than is usually required by the exhaust to heat the sensor to operating temperature.

The reference voltage of the Oxygen Sensor (O2) varies according to the oxygen content. This variation can range from 0.1 to 0.9 volts, when there are 0.1 volts, it indicates a poor leakage, and when there are 0.9 volts, it indicates a rich leakage.

When the DTC code is set, it means that the O2 is stuck for a certain time, it may even be inactive

• The Check Engine light turns on.
• Fuel economy is affected.
• Exhaust emissions are increasing.

The reasons to set the code P0156 OBDII can be

• It may be that one of the cables is in contact with exhaust components.
• There may be holes in the exhaust that are very close to the oxygen sensor.
• The voltage signal from the oxygen sensor may be short-circuited.
• The Oxygen (O2) sensor may be defective.

To solve the fault code P0156 OBD2, you can do this:

• First, use a scan tool to check the signal voltage of the oxygen sensor in bank number 2 with the engine temperature in normal operation. Watch if it is stuck at a low level. Now, increase the RPM for a few seconds and see if the reading is affected. If you start working with increased RPM, the failure may be due to possible holes in the exhaust near the Oxygen (O2) Sensor and thus cause a false tilt. If the exhaust is not defective, you can replace the Oxygen Sensor (O2).
• If the RPM reading remains low, unplug the O2 Sensor and watch the reading increase to approximately 0.5 volts. If so, you can check for the presence of water or other elements in the Oxygen Sensor If you don't find anything, you can change the Oxygen Sensor (O2) as it may be shorted.
• If the voltage reading after the O2 Sensor is disconnected is still low, you may want to check the wiring system. Using a voltmeter and the unplugged Oxygen (O2) Sensor, check the voltage in the signal circuit at the O2 Sensor connector on the PCM Note that the result may vary by model, but it should be around 0.5 volts. If it exceeds this voltage, you can repair a short circuit to voltage in the signal circuit.
• Changes the Oxygen Sensor (O2).