P0138: O2 Oxygen Sensor Circuit High Voltage (Bank1, Sensor2)

What Does The P0138 Code Mean?

The Heated Oxygen Sensor (2) located rear of catalytic converter produces an output signal relative to oxygen storage capacity of catalytic converter. Bank 1 is the side of the engine that contains the #1 cylinder.

Ho2S 2 signal is less active than signal produced by front oxygen sensor. This code sets when HO2 Sensor voltage is greater than 999 mV for more than 2 minutes (time depends on model. Could be as high as 4 minutes)

What Are The Symptoms Of The P0138 Code?

There may be no noticeable symptoms except for MIL illumination. Possible high fuel pressure can over rich the system.

What Are The Potential Causes Of The P0138 Code?

A code P0138 may mean that one or more of the following has happened:

• Faulty O2 sensor
• Short to battery voltage in O2 sensor signal circuit
• High fuel pressure (not as likely)

How Can You Fix The P0138 Code?

Here are some potential solutions:

• Replace O2 sensor
• Repair short to battery voltage in o2 sensor signal circuit

Recommended Parts

Below are some recommended auto parts to help you address the trouble code affecting your vehicle and get it running smoothly again:

>>> O2 Sensor
>>> Twippo 372Pcs Waterproof Wire Connectors Kit

Note: During the purchasing process, please check carefully whether the part you want to buy fits your car!

Check This Video For Reference

P0138 Infographic - 1 Minute Summary

Reference Sources

• Technical Service Bulletin for P0138 – Ford
• Engine Control Service Manual for P0138 – Pages 44-45.