What is the P0138 fault codes? What does Oxygen Sensor circuit High Voltage (Bank 1 Sensor 2) malfunction mean? What is the best way to fix P0138 fault code What are the causes for the P0138 fault ?….
What is the P0138 Fault code? What does it signify?
When the voltage signal from your rear O2 sensor becomes too high, the code P0138 will trigger.
Modern cars come with at least two oxygen sensors. Both sensors detect oxygen levels in the exhaust stream. The data from both sensors is used by PCM to perform different functions. The upstream oxygen sensor (Sensor 1), is the first sensor. This sensor acts as the primary feedback input to the “closed loop fuel system” and aids the PCM in regulating the vehicle’s ratio of air to fuel.
Sensor 2, also known downstream (after the catalyst), monitors the catalytic converter’s oxygen storage capacity.
Many mechanics don’t know this. If the PCM is constantly receiving incorrect parameters from an upstream sensor it sets that downstream sensor as primary and adjusts fuel based on what it has received from that sensor.
When the downstream sensor transmits a very high voltage signal (greater that 1.1 volts) for longer than 10 seconds, a P0138 code will be set. Bank 1 is the indication that the fault lies on the first cylinder of the engine. It applies to either “V” or boxer engines. Row 1 is where the spark plug #1 is. Sensor 2 is the downstream oxygen sensor that follows the catalyst.
What causes the P0138 Faultcode?
The most common reason for P0138 is a defective oxygen sensor. However, this error can be caused by many other reasons. The most common cause is:
- – Connectors or cables that are damaged
- – Defective oxygen sensor
- – The engine is running at a high level of performance due to fuel system problems (such as high fuel pressure).
What are the symptoms for P0138 Fault Codes?
- – Illumination for the check engine light
- Engine misfire
- – High fuel consumption
- – Idle irregularity
- – The engine is not able to accelerate due to lack of power
- – Engine stalling
If you notice any of these symptoms in your vehicle, your mechanic should check it.
How to Fix the P0138 Fault Code
- – Tests of O2 sensor voltages. During the test, both sensors’ data should be compared.
- – Check O2 sensor connectors and cables for corrosion. If necessary, repair.
- – Make sure the O2 sensor is free from contamination and any damage. The sensor must be replaced if it is defective.
- Engine oil and coolant leaks which could pollute the O2 sensor should be checked.
- – Before installing the sensor, exhaust leaks should be checked.
- – Make sure to check if the catalyst has become damaged or blocked.
- It is necessary to replace a faulty injector or leaking one.
- For further diagnosis, specific tests may be performed.
What’s the significance of the P0138 fault code?
The PCM is unable to control the engine’s fuel/air ratio. This could lead to blockage of the catalyst, fouling the spark plugs, and excessive carbon buildup in the engine. This fault should be fixed immediately as it can affect engine performance as well as driving comfort.
