AutoCodes – Toyota – P0138 2009 Toyota Prius

P0138 2009 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 2009 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 6,534

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 2009 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 2009 Toyota Prius - Oxygen Sensor Circuit High Voltage Bank 1 Sensor 2 - AutoCodes.com — P0138 2009 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 2009 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 2009 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 2009 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 2009 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 2009 Toyota Prius Code

1. What does the OBDII code P0138 for a 2009 Toyota Prius indicate?

The code P0138 in a 2009 Toyota Prius indicates an Oxygen Sensor Circuit High Voltage condition in Bank 1 Sensor 2.

2. What are the common symptoms of a P0138 code in a 2009 Toyota Prius?

Common symptoms of a P0138 code in a 2009 Toyota Prius include poor fuel efficiency, rough idling, and potential engine misfires.

3. What are the possible causes of the P0138 code in a 2009 Toyota Prius?

Possible causes of a P0138 code in a 2009 Toyota Prius include a faulty oxygen sensor, wiring issues, exhaust leaks, or a malfunctioning catalytic converter.

4. How can I diagnose the P0138 code in a 2009 Toyota Prius?

To diagnose a P0138 code in a 2009 Toyota Prius, you can use an OBDII scanner to read the code, visually inspect the oxygen sensor and its wiring, and check for any exhaust leaks.

5. How can I repair a P0138 code in a 2009 Toyota Prius?

Repairing a P0138 code in a 2009 Toyota Prius may involve replacing the Bank 1 Sensor 2 oxygen sensor, repairing any damaged wiring, fixing exhaust leaks, or replacing the catalytic converter if necessary.

6. Can I drive my 2009 Toyota Prius with a P0138 code?

It is not recommended to drive your 2009 Toyota Prius with a P0138 code for an extended period as it can lead to decreased fuel efficiency and potential damage to the engine and catalytic converter.

7. How much does it cost to fix a P0138 code in a 2009 Toyota Prius?

The cost to fix a P0138 code in a 2009 Toyota Prius can vary depending on the exact cause of the issue, but it may range from $100 to $500 or more for parts and labor.

8. How often does the oxygen sensor need to be replaced in a 2009 Toyota Prius?

The oxygen sensor in a 2009 Toyota Prius typically needs to be replaced every 60,000 to 90,000 miles, but it can vary based on driving conditions and maintenance practices.

9. Can a P0138 code in a 2009 Toyota Prius cause the Check Engine light to come on?

Yes, a P0138 code in a 2009 Toyota Prius can trigger the Check Engine light to illuminate on the dashboard as it indicates a problem with the oxygen sensor circuit.

10. Is it possible to reset the P0138 code in a 2009 Toyota Prius without fixing the underlying issue?

While you can clear the code temporarily, it is not recommended to reset the P0138 code in a 2009 Toyota Prius without addressing the root cause, as the issue may persist and lead to further problems.