Engine-CodesScion – P0138 Scion

P0138 Scion Code - Oxygen Sensor Circuit High Voltage Bank 1 Sensor 2

Quick Answer

The P0138 diagnostic trouble code (DTC) for Scion vehicles indicates an issue with the Oxygen Sensor Circuit High Voltage Bank 1 Sensor 2. Common causes include Faulty oxygen sensor, Wiring or connector issues in the oxygen sensor circuit, Exhaust leaks near the oxygen sensor. 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 Scion indicates Oxygen Sensor Circuit High Voltage Bank 1 Sensor 2.
Common causes
Common causes include Faulty oxygen sensor, Wiring or connector issues in the oxygen sensor circuit, Exhaust leaks near the oxygen sensor.
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.
Table of contents Created and updated by William Orellana on Sep 07, 2024
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Code P0138 Scion Description

The P0138 diagnostic trouble code (DTC) for Scion vehicles indicates an issue with the Oxygen Sensor Circuit High Voltage Bank 1 Sensor 2. This code specifically relates to the second oxygen sensor on the bank 1 side of the engine, which is typically found after the catalytic converter. The oxygen sensor plays a crucial role in monitoring the oxygen levels in the exhaust gases and providing feedback to the engine control module (ECM) to adjust the air-fuel mixture for optimal combustion.

OBDII Code P0138 Scion - Oxygen Sensor Circuit High Voltage Bank 1 Sensor 2
P0138 Scion Code - Oxygen Sensor Circuit High Voltage Bank 1 Sensor 2

Common Causes of P0138 Scion

  1. Faulty oxygen sensor
  2. Wiring or connector issues in the oxygen sensor circuit
  3. Exhaust leaks near the oxygen sensor
  4. Engine running rich due to a faulty fuel injector
  5. ECM software issues

Symptoms of P0138 Scion

  1. Check engine light illuminated on the dashboard
  2. Decreased fuel efficiency
  3. Rough idling or stalling
  4. Increased emissions output
  5. Engine running too lean or too rich

How to Fix P0138 Scion

  1. Begin by diagnosing the root cause of the high voltage reading, which may involve using a scan tool to monitor the oxygen sensor's output.
  2. Inspect the oxygen sensor wiring and connectors for any signs of damage or corrosion. Repair or replace as necessary.
  3. Check for exhaust leaks near the oxygen sensor and repair them to ensure proper sensor readings.
  4. Test the fuel injectors to ensure they are functioning correctly and replace any faulty injectors if needed.
  5. Clear the DTC with a scan tool and test drive the vehicle to ensure the issue has been resolved.

Cost to Fix P0138 Scion

The typical cost for repairing a P0138 code on a Scion vehicle can range from $150 to $400, depending on the specific cause of the issue and the labor rates at the auto repair shop. Parts such as an oxygen sensor or fuel injector may need to be replaced, along with the cost of diagnostic time and labor. It's important to consult with a trusted mechanic or dealership for a more accurate estimate based on the specific circumstances of the vehicle. Labor rates at auto repair shops can vary, so it's advisable to inquire about rates in your local area.

Tech Notes for P0138 Scion

Replacing the Oxygen Sensor Bank 1 Sensor 2 (Rear Oxygen Sensor Bank 1 or Downstream Oxygen Sensor Bank 1) usually takes care of the problem.

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Information for Specific Scion Models

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.

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