AutoCodes – Toyota – P0138 2007 Toyota Prius

P0138 2007 Toyota Prius Code - Oxygen Sensor Circuit High Voltage Bank 1 Sensor 2

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 2007 Toyota Prius indicates Oxygen Sensor Circuit High Voltage Bank 1 Sensor 2.
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 11,733

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 Jul 04, 2020

Description
Step-by-Step Diagnostic Guide
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P0138 2007 Toyota Prius 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 2007 Toyota Prius - Oxygen Sensor Circuit High Voltage Bank 1 Sensor 2 - AutoCodes.com — P0138 2007 Toyota Prius Code - Oxygen Sensor Circuit High Voltage Bank 1 Sensor 2

What does this mean?

What are the Possible Causes of the DTC P0138 2007 Toyota Prius?

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 2007 Toyota Prius?

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 is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0138 2007 Toyota Prius 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.

Need more information about the P0138 2007 Toyota Prius code?

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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 2007 Toyota Prius Code

1. What does the OBDII code P0138 for a 2007 Toyota Prius indicate?

This code indicates a high voltage condition in the oxygen sensor circuit of Bank 1 Sensor 2 in the exhaust system.

2. What are the common symptoms of a P0138 code in a 2007 Toyota Prius?

Common symptoms include poor fuel economy, rough idling, hesitation during acceleration, and the illumination of the check engine light.

3. What are the potential causes of a P0138 code in a 2007 Toyota Prius?

Possible causes include a faulty oxygen sensor, wiring issues in the sensor circuit, an exhaust leak, or a problem with the engine's fuel mixture.

4. How can I diagnose the source of a P0138 code in my 2007 Toyota Prius?

Diagnosis typically involves using a scan tool to monitor the oxygen sensor's voltage readings, checking for any visible damage to the sensor or its wiring, and inspecting the exhaust system for leaks.

5. Can a P0138 code in a 2007 Toyota Prius be repaired at home?

Depending on your level of automotive knowledge and skills, you may be able to replace the oxygen sensor yourself if that is the root cause. However, diagnosing and repairing wiring or exhaust leaks may require professional assistance.

6. How important is it to address a P0138 code in a 2007 Toyota Prius promptly?

Ignoring a P0138 code can lead to decreased fuel efficiency, increased emissions, and potential damage to the catalytic converter over time. It is advisable to address this issue promptly.

7. Is it safe to continue driving my 2007 Toyota Prius with a P0138 code?

While the vehicle may still be driveable with a P0138 code, it is recommended to have the issue diagnosed and repaired as soon as possible to prevent further damage and ensure optimal performance.

8. How much does it typically cost to repair a P0138 code in a 2007 Toyota Prius?

The cost of repair can vary depending on the root cause of the issue. Replacing the oxygen sensor itself may cost around $100 to $200, while addressing wiring or exhaust leaks could increase the total repair cost.

9. Can a P0138 code in a 2007 Toyota Prius cause the vehicle to fail an emissions test?

Yes, a P0138 code indicates an issue with the oxygen sensor circuit, which can lead to increased emissions. If not addressed, this could cause the vehicle to fail an emissions test.

10. How long does it typically take to repair a P0138 code in a 2007 Toyota Prius?

The repair time for a P0138 code can vary based on the specific issue and the expertise of the technician. Replacing the oxygen sensor usually takes around 1-2 hours, but additional diagnosis and repairs may extend the duration.