AutoCodes – KIA – P0138 KIA

P0138 KIA Code - HO2S12 Circuit High Voltage

Quick Answer

The Heated Oxygen Sensor 2 (HO2S) (Rear O2 Sensor), after three way catalyst (manifold), monitors the oxygen level in the exhaust gas on each bank. Common causes include Faulty Rear Heated Oxygen Sensor Bank 1, Rear Heated Oxygen Sensor Bank 1 harness is open or shorted, Rear Heated Oxygen Sensor Bank 1 circuit poor electrical connection. Severity is Moderate - service should be scheduled soon. The vehicle may still be drivable for short trips if it runs normally, but avoid hard driving and repair it soon.

What it means: P0138 KIA indicates HO2S12 Circuit High Voltage.
Common causes: Common causes include Faulty Rear Heated Oxygen Sensor Bank 1, Rear Heated Oxygen Sensor Bank 1 harness is open or shorted, Rear Heated Oxygen Sensor Bank 1 circuit poor electrical connection.
Severity: Moderate - service should be scheduled soon.
Can I drive?: The vehicle may still be drivable for short trips if it runs normally, but avoid hard driving and repair it soon.

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Code Popularity 25,568

How popular is this code, among other codes? Low

Repair Importance Level

Moderate (Service soon) (2 / 3)

Repair Difficulty Level

Intermediate (2 / 3)

What is this?

Table of contents Created and updated by William Orellana on Jun 14, 2020

Description
Step-by-Step Diagnostic Guide
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
FAQs
Comments
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Code P0138 KIA Description

The Heated Oxygen Sensor 2 (HO2S) (Rear O2 Sensor), after three way catalyst (manifold), monitors the oxygen level in the exhaust gas on each bank. For optimum catalyst operation, the air fuel mixture (air-fuel ratio) must be maintained near the ideal stoichiometric ratio. The HO2S output voltage changes suddenly in the vicinity of the stoichiometric ratio. The Engine Control Module (ECM) adjusts the fuel injection time so that the air-fuel ratio is nearly stoichiometric. The HO2S generates a voltage between 0.1 and 0.9 V in response to oxygen in the exhaust gas. If the oxygen in the exhaust gas increases, the air-fuel ratio becomes Lean. The ECM interprets Lean when the HO2S voltage is below 0.45 V. If the oxygen in the exhaust gas decreases, the air-fuel ratio becomes Rich. The ECM interprets Rich when the HO2S voltage is above 0.45 V.

OBDII Code P0138 KIA - HO2S12 Circuit High Voltage - AutoCodes.com — P0138 KIA Code - HO2S12 Circuit High Voltage

What does this mean?

What are the Possible Causes of the DTC P0138 KIA?

Faulty Rear Heated Oxygen Sensor Bank 1
Rear Heated Oxygen Sensor Bank 1 harness is open or shorted
Rear Heated Oxygen Sensor Bank 1 circuit poor electrical connection
Intake air leaks
Exhaust gas leaks
Inappropriate fuel pressure
Faulty fuel injectors

How to Fix the DTC P0138 KIA?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What does this mean?

Code Tech Notes

Replacing the Rear Heated Oxygen Sensor Bank 1 usually takes care of the problem.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0138 KIA code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

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About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

Frequently Asked Questions about P0138 KIA Code

1. What are the common symptoms of OBDII code P0138 in a KIA, which indicates HO2S12 Circuit High Voltage?

Symptoms may include poor fuel efficiency, rough idling, engine hesitation, or even the illumination of the Check Engine Light.

2. What are the possible causes of OBDII code P0138 in a KIA related to HO2S12 Circuit High Voltage?

Common causes include a faulty oxygen sensor, issues with the wiring or connectors in the oxygen sensor circuit, or a problem with the engine's fuel system.

3. How can I diagnose the HO2S12 Circuit High Voltage issue in my KIA triggering OBDII code P0138?

A thorough diagnosis typically involves checking the oxygen sensor's voltage output, inspecting the sensor's wiring and connectors for damage, and verifying the fuel system's operation.

4. Can a dirty or contaminated oxygen sensor cause OBDII code P0138 in a KIA?

Yes, a dirty or contaminated oxygen sensor may provide inaccurate readings, leading to the triggering of code P0138 related to HO2S12 Circuit High Voltage.

5. What are some repair tips for addressing OBDII code P0138 in a KIA due to HO2S12 Circuit High Voltage?

Repair options may include cleaning or replacing the oxygen sensor, repairing damaged wiring or connectors, and ensuring proper fuel system operation.

6. Is it safe to continue driving my KIA with OBDII code P0138 indicating HO2S12 Circuit High Voltage?

It is generally not recommended to drive with this issue unresolved, as it can lead to decreased fuel efficiency and potential engine performance problems.

7. Can resetting the Check Engine Light make OBDII code P0138 related to HO2S12 Circuit High Voltage disappear permanently?

Simply resetting the Check Engine Light will not fix the underlying problem causing code P0138. The issue should be diagnosed and repaired to prevent the code from reoccurring.

8. Are there any DIY methods to troubleshoot OBDII code P0138 in a KIA connected to HO2S12 Circuit High Voltage?

While basic checks like inspecting the oxygen sensor wiring and connectors can be done DIY, a comprehensive diagnosis and repair may require professional tools and expertise.

9. How can a mechanic reset OBDII code P0138 after resolving the HO2S12 Circuit High Voltage issue in a KIA?

After fixing the underlying problem, a mechanic can use an OBDII scanner to clear the trouble code and reset the Check Engine Light in the KIA.

10. What is the typical cost to repair OBDII code P0138 related to HO2S12 Circuit High Voltage in a KIA?

The cost of repair can vary depending on the exact cause of the issue, but it may involve expenses for parts like a new oxygen sensor and labor for diagnosis and installation, ranging from $100 to $300 or more.