P0158 Code – What Does It Mean & How To Fix It

This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.

Causes

Common causes for this code include:

• Failed rear oxygen sensor or connected heater circuit
• Wiring is touching the exhaust or its relative parts
• The engine is running rich (will present with other codes) 
• Exhaust leaks in the PCM are causing it to be excessively rich, resulting in a Bank 2, sensor 2 reading that is outside of the normal range.
• Shorts, breaks, or exposed wiring or bad PCM (rare)

Symptoms

The symptoms of a P0158 code are: 

• The Check Engine Light will turn on
• Rough idle (Rich condition) 
• Lack of power 
• Poor fuel consumption 
• Abnormal engine noises or vibrations 

Diagnosis

To diagnose a P0158 DTC code, a technician would:

1. A mechanic will use an OBD-II scanner to pull all present trouble codes that have been stored by the power control module (PCM). 
2. He will then review the freeze frame data for these codes and write down relevant information that can be used to further diagnose issues. 
3. He would then clear the codes and drive the vehicle to see if the P0158 returns. 
4. If no other trouble codes are pulled, he would inspect for proper wiring to the rear oxygen sensor. 
5. He will check for both shorted and open circuits or breaks in wiring as well as look closely at components like sensors, hoses, gaskets, etc., that could potentially cause an exhaust leak. 
6. Upon further inspection, determine if the harness around the #2 oxygen sensor is touching part of the cat converter causing too high voltage readings which causes this code.
7. Once he has determined if there is a problem with the sensor itself (by testing its output), begins by checking for shortened connections and breaks in the harnesses of the sensor. If all lines are intact and free from shorts or breaks, then it is likely that there is a problem with the power control module.

Common mistakes

The following are common mistakes when diagnosing the trouble code P0158:

A technician will mistakenly replace the oxygen sensors in bank 2 when he should be inspecting for exhaust leaks and touching wires.

A technician might clear the codes prematurely, when in fact the real issue was not properly diagnosed.

How serious is this?

A P0158 code is not typically serious. It simply means that there is a problem in the bank 2, sensor 2 circuit and the power control module (PCM) has stored a code for future reference. There are little to no adverse effects on vehicle performance when this trouble code is present. 

In some cases, it can be indicative of an ongoing or soon-to-be more severe problem. For instance, if the rear oxygen sensor was not receiving proper voltage earlier when it was healthy, then chances are that its harness touched something hot like exhaust piping resulting in an open circuit. More severe damage could have been done to other parts of the engine before this code manifested itself as a result of less than optimal running conditions. This often results in secondary failures once the defect is discovered.

What repairs can fix the code?

The following are solutions that may fix this problem:

• Make any required repairs to correct the excessive fuel pressure.
• Repair an open circuit in the wiring around the #2 oxygen sensors. 
• Investigate for exhaust leaks by inspecting closely all gaskets, hoses, and pipes that lead to or from Bank 2, sensor 2. If any are found to be leaking, replace them.
• If it's necessary, replace the temperature sensor in the engine coolant.

Related codes

A P0158 is related to and may be accompanied by the following codes:

• P0155 – Heated Oxygen Sensor (H2O) Circuit High Voltage Bank 1 Sensor 2
• P0156 – Heated Oxygen Sensor (H2O) Circuit Shorted to Ground Bank 1 Sensor 2 
• P0230 – Fuel Pump Secondary Circuit Malfunction 
• P0236 – Fuel Pump Cutoff System Performance

How much does it cost to fix the P0158 code?

The repair cost of a P0158 code depends on the type of component that needs to be replaced. For an oxygen sensor, it will cost $200–$600. On average, however, this code would require less than $100 in repairs.

Conclusion

In conclusion, the P0158 code is a generic trouble code that occurs when there is a problem within the oxygen sensor circuit in bank 2, sensor 2. There are cases where this can be repaired by performing simple repairs to components around it or replacing #2 oxygen sensors themselves. In other cases, however, it may require more expensive repairs such as repairing an open wire harness or faulty power control module.