AutoCodes – Toyota – P0138 2002 Toyota Highlander

P0138 2002 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 2002 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 3,627

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 2002 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 2002 Toyota Highlander - Oxygen Sensor Circuit High Voltage Bank 1 Sensor 2 - AutoCodes.com — P0138 2002 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 2002 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 2002 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 2002 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 2002 Toyota Highlander code?

Need more information on how to fix the P0138 2002 Toyota Highlander code? Get Access to Factory Service Manuals

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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 2002 Toyota Highlander Code

1. What are the common symptoms of OBDII code P0138 on a 2002 Toyota Highlander?

- Common symptoms include poor fuel efficiency, rough idling, and the illumination of the check engine light.

2. What does the OBDII code P0138 for a 2002 Toyota Highlander indicate?

- The code P0138 indicates that there is a high voltage condition in the oxygen sensor circuit of Bank 1 Sensor 2.

3. What are the possible causes of OBDII code P0138 on a 2002 Toyota Highlander?

- Potential causes include a faulty oxygen sensor, damaged wiring or connectors, exhaust leaks, or issues with the engine's computer.

4. How can I diagnose the OBDII code P0138 on my 2002 Toyota Highlander?

- Diagnosis involves using an OBDII scanner to read the code, inspecting the wiring and connectors, and testing the oxygen sensor's voltage output.

5. Is it safe to drive my 2002 Toyota Highlander with OBDII code P0138?

- It is generally safe to drive the vehicle with this code, but it is recommended to address the issue promptly to prevent potential damage to the catalytic converter.

6. Can I repair OBDII code P0138 on my 2002 Toyota Highlander myself?

- Depending on your mechanical skills, you may be able to replace the oxygen sensor, check and repair wiring, or address other possible causes with the help of repair guides.

7. How much does it typically cost to repair OBDII code P0138 on a 2002 Toyota Highlander?

- The cost can vary depending on the exact cause of the issue, but it may range from $100 to $300 for parts and labor.

8. Are there any tips to prevent OBDII code P0138 from occurring again on my 2002 Toyota Highlander?

- Regularly inspecting and maintaining the oxygen sensors, ensuring proper engine performance, and addressing any issues promptly can help prevent the code from reoccurring.

9. Will resetting the check engine light resolve OBDII code P0138 on my 2002 Toyota Highlander?

- Resetting the check engine light may temporarily clear the code, but it is important to diagnose and fix the underlying issue to prevent the code from coming back.

10. How long does it take to repair OBDII code P0138 on a 2002 Toyota Highlander?

- Repair times can vary based on the specific cause of the code, but it typically takes a few hours to a half-day for a professional mechanic to diagnose and repair the issue.