AutoCodes – Toyota – P0138 2006 Toyota Highlander

P0138 2006 Toyota Highlander 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 2006 Toyota Highlander 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 6,008

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 2006 Toyota Highlander 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 2006 Toyota Highlander - Oxygen Sensor Circuit High Voltage Bank 1 Sensor 2 - AutoCodes.com — P0138 2006 Toyota Highlander Code - Oxygen Sensor Circuit High Voltage Bank 1 Sensor 2

What does this mean?

What are the Possible Causes of the DTC P0138 2006 Toyota Highlander?

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 2006 Toyota Highlander?

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 2006 Toyota Highlander 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 2006 Toyota Highlander 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 2006 Toyota Highlander Code

1. What does OBDII code P0138 mean for a 2006 Toyota Highlander?

- OBDII code P0138 in a 2006 Toyota Highlander indicates a high voltage condition in the oxygen sensor circuit of Bank 1 Sensor 2.

2. What are the common symptoms of OBDII code P0138 in a 2006 Toyota Highlander?

- Common symptoms of P0138 may include decreased fuel efficiency, rough idling, engine misfires, and the illumination of the check engine light.

3. What are the possible causes of OBDII code P0138 in a 2006 Toyota Highlander?

- The main causes of P0138 include a faulty oxygen sensor, damaged wiring or connectors in the sensor circuit, exhaust leaks, or issues with the engine's air-fuel ratio.

4. How can I diagnose OBDII code P0138 in my 2006 Toyota Highlander?

- Diagnosing P0138 involves using an OBDII scanner to retrieve the code, inspecting the oxygen sensor and related wiring, checking for exhaust leaks, and verifying the air-fuel ratio.

5. Can I drive my 2006 Toyota Highlander with OBDII code P0138?

- It is not recommended to drive your Highlander with P0138 for an extended period as it can lead to further damage and decreased engine performance. It's best to address the issue promptly.

6. How do I repair OBDII code P0138 in a 2006 Toyota Highlander?

- Repairing P0138 may involve replacing the Bank 1 Sensor 2 oxygen sensor, repairing damaged wiring or connectors, fixing any exhaust leaks, and ensuring the proper air-fuel ratio.

7. Is it possible to reset OBDII code P0138 in a 2006 Toyota Highlander without fixing the issue?

- While you can clear the code with an OBDII scanner, it is not recommended to reset P0138 without addressing the underlying problem, as it will likely return and potentially cause more issues.

8. Are there any DIY tips for fixing OBDII code P0138 in a 2006 Toyota Highlander?

- DIY tips include checking the sensor's connections, inspecting for visible damage, ensuring proper installation, and following a step-by-step guide if replacing the oxygen sensor yourself.

9. How much does it cost to fix OBDII code P0138 in a 2006 Toyota Highlander at a repair shop?

- The cost to fix P0138 can vary depending on the root cause, but it may range from $100 to $300 for parts and labor if replacing the oxygen sensor, addressing wiring issues, or fixing exhaust leaks.

10. Will OBDII code P0138 in a 2006 Toyota Highlander affect emissions testing?

- Yes, having an unresolved P0138 code can cause your Highlander to fail emissions testing, as it indicates a problem with the oxygen sensor circuit, which plays a crucial role in monitoring emissions.