AutoCodes – Toyota – P0138 2001 Toyota Highlander

P0138 2001 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 2001 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 4,082

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 2001 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 2001 Toyota Highlander - Oxygen Sensor Circuit High Voltage Bank 1 Sensor 2 - AutoCodes.com — P0138 2001 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 2001 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 2001 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 2001 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 2001 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 2001 Toyota Highlander Code

1. What is OBDII code P0138 for a 2001 Toyota Highlander?

- OBDII code P0138 indicates an issue with the Oxygen Sensor Circuit High Voltage Bank 1 Sensor 2 in a 2001 Toyota Highlander.

2. What are the common symptoms of OBDII code P0138 in a 2001 Toyota Highlander?

- Common symptoms of P0138 may include poor fuel economy, rough idling, engine misfires, and the illumination of the Check Engine Light.

3. What are the possible causes of OBDII code P0138 in a 2001 Toyota Highlander?

- The common 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 2001 Toyota Highlander?

- To diagnose P0138, you can use an OBDII scanner to retrieve the code, visually inspect the sensor and its wiring, check for exhaust leaks, and perform voltage tests on the sensor.

5. Can I drive my 2001 Toyota Highlander with OBDII code P0138?

- It is generally not recommended to drive your vehicle with an unresolved P0138 code, as it can lead to decreased fuel efficiency and potential damage to the catalytic converter.

6. How do I repair OBDII code P0138 in my 2001 Toyota Highlander?

- Repairing P0138 may involve replacing the oxygen sensor, repairing damaged wiring or connectors, fixing exhaust leaks, or addressing any underlying issues affecting the air-fuel ratio.

7. Can a DIY enthusiast fix OBDII code P0138 in a 2001 Toyota Highlander?

- Depending on your experience and tools, a DIY enthusiast may be able to repair P0138 by replacing the oxygen sensor or addressing simple wiring issues. However, more complex repairs may require professional assistance.

8. How much does it cost to repair OBDII code P0138 in a 2001 Toyota Highlander?

- The cost of repairing P0138 can vary based on the specific issue causing the code. Replacing an oxygen sensor may cost between $100 to $300, while addressing wiring or exhaust leaks could increase the overall repair cost.

9. How often should the oxygen sensor be replaced in a 2001 Toyota Highlander?

- The oxygen sensor typically needs replacement every 60,000 to 90,000 miles, but this can vary based on driving conditions and vehicle usage. Regular maintenance can help prevent issues like P0138.