P0158 - 02 HIGH VOLTAGE CIRCUIT SENSOR (BANK 2, SENSOR 2)

The diagnostic code P0158 OBDII means that there is a failure in the Oxygen (O2) Sensor that is located in bank number 2. The fault shows that the signal voltage is above the expected level.

The Oxygen Sensor (O2) has four wires. Two of these are connected to the sensor heating element and the other two are connected to the sensor. One of the heating element wires provides a voltage that must be high or equal to the battery voltage, while the other wire is grounded.

The Powertrain Control Module (PCM) gives a 0.5 volts reference signal to the Oxygen (O2) Sensor, although this voltage may vary depending on the oxygen content of the exhaust. The PCM also provides a ground to the O2 sensor. It should be noted that changes in oxygen content cause resistance to vary. As the resistance changes, the voltage supplied by the PCM is affected, so it can also change between 0.1 and 0.9 volts.

When reading of 0.1 volts is obtained, it means that the mixture is poor, and when this value is around 0.9 volts, it means that the mixture is rich. This voltage variation is monitored by the PCM and when the voltage is higher than normal, the code P0158 OBD2 is set.

• The Check Engine light turns on.
• You may notice a lack of power in the engine.
• The fuel may not be as efficient.

A diagnostic code P0158 OBD2 means that one or more of the following problems have occurred:

• Some Oxygen (O2) Sensor cable may be in contact with a component in the exhaust.
• Holes in the exhaust causing an excessively high sensor reading.
• Perhaps, there is a short in the signal circuit.
• The Oxygen Sensor (O2) may be defective.

If you have a fault code P0158 OBDII, you can do the following to solve it:

• You can check all the components of the exhaust system, some of them may be rubbing against one of the circuit wires. Repair if you find a problem like the one mentioned above.
• Verify that the wiring of the rear Oxygen Sensor is not short-circuited or the wires are worn. In case you find inconsistency in one of these, you can repair or even replace it if necessary.
• With the engine running, watch the oxygen sensor voltage 2. If you notice that the sensor voltage drops or falls when idling, you can change it since it is showing slowness.
• Check that the sensor has good ground.
• If a DTC code is present indicating problems with the ECT sensor (Coolant Temperature Sensor), you should check for proper engine temperature.
• Change Oxygen (O2) Sensor number 2.