Is P0138 the front or rear oxygen sensor?
4 Answers
P0138 is the rear oxygen sensor. Below is an introduction about the engine assembly: 1. Introduction: The engine assembly, also known as the engine, is a machine capable of converting one form of energy into another more useful form of energy. 2. Principle: It usually converts chemical energy into mechanical energy (the conversion of electrical energy into mechanical energy is referred to as an electric motor). Sometimes, it applies to both power generation devices and the entire machine including the power unit, such as gasoline engines and aircraft engines. 3. Development: Looking back at the history of engine creation and development, it has gone through two stages: external combustion engines and internal combustion engines.
When I encountered the engine malfunction light, the scan showed a P0138 trouble code, which from experience clearly points to a high voltage issue with the rear oxygen sensor. The rear oxygen sensor is typically located behind the catalytic converter, monitoring emission data to help the engine adjust the fuel mixture. If the voltage abnormally rises, common causes include a faulty sensor itself or a wiring short circuit, affecting fuel consumption and emissions. My car once experienced a spike in fuel consumption due to this, and it returned to normal only after replacing the new sensor. Remember, front oxygen sensor codes like P0130 or P0136 are different—they are positioned before the catalytic converter and serve different functions. If you encounter P0138, don’t delay too long to avoid damaging the catalytic converter. I recommend sending it for repair promptly to prevent major safety hazards. Regularly checking for aging sensor connectors can also help prevent such issues.
After studying cars for so long, I finally figured out that P0138 is the trouble code for the rear oxygen sensor. It indicates that the voltage output exceeds the upper limit in the system, located downstream of the catalytic converter, ensuring proper exhaust purification. Compared to the front oxygen sensor, P0138 specifically targets the rear component, and abnormal voltage suggests possible internal short circuits or wiring harness breaks. My friend's car had this issue with the engine light constantly on, and diagnosis only took half an hour to replace the part. The fault can also reduce fuel efficiency, and I found in my research that emission control relies on this sensor, so timely action is crucial. Regular self-checks with a diagnostic tool can help detect problems early.
During vehicle maintenance, it was found that the P0138 trouble code specifically indicates a high voltage in the rear oxygen sensor circuit. The rear oxygen sensor is located downstream of the catalytic converter and monitors exhaust gases to optimize engine combustion. Excessive voltage may be caused by component aging or wiring corrosion. My troubleshooting process always starts by checking the rear oxygen sensor connections, and replacing the faulty sensor results in noticeable performance recovery. This is not an issue with the front oxygen sensor, as the codes clearly differentiate between them. Simple maintenance can extend the sensor's lifespan.
