P0138 2018 Toyota RAV4 Code - Oxygen Sensor Circuit High Voltage Bank 1 Sensor 2
Quick Answer
In order to obtain a high purification rate of the Carbon Monoxide (CO), Hydrocarbon (HC), and Nitrogen Oxide (NOx) components in the exhaust gas, a Three-Way Catalytic Converter (TWC) is used. Common causes include Faulty Oxygen Sensor Bank 1 Sensor 2, Oxygen Sensor Bank 1 Sensor 2 harness is open or shorted, Oxygen Sensor Bank 1 Sensor 2 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 2018 Toyota RAV4 indicates Oxygen Sensor Circuit High Voltage Bank 1 Sensor 2.
- Common causes
- Common causes include Faulty Oxygen Sensor Bank 1 Sensor 2, Oxygen Sensor Bank 1 Sensor 2 harness is open or shorted, Oxygen Sensor Bank 1 Sensor 2 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.
Code P0138 2018 Toyota RAV4 Description
The heated oxygen sensor is located behind the TWC and detects the oxygen concentration in the exhaust gas. Since the sensor is integrated with the heater that heats the sensing portion, it is possible to detect the oxygen concentration even when the intake air volume is low (the exhaust gas temperature is low).
When the air-fuel ratio becomes lean, the oxygen concentration in the exhaust gas is high. The heated oxygen sensor informs the ECM that the post-TWC air-fuel ratio is lean (low voltage, i.e. less than 0.45 V).
Conversely, when the air-fuel ratio is richer than the stoichiometric air-fuel level, the oxygen concentration in the exhaust gas is low. The heated oxygen sensor informs the ECM that the post-TWC air-fuel ratio is rich (high voltage, i.e. more than 0.45 V). The heated oxygen sensor has the property of changing its output voltage drastically when the air-fuel ratio is close to the stoichiometric level.
The ECM uses the supplementary information from the heated oxygen sensor to determine whether the air-fuel ratio after the TWC is rich or lean and adjusts the fuel injection duration accordingly. Thus, if the heated oxygen sensor is working improperly due to internal malfunctions, the ECM is unable to compensate for deviations in the primary air-fuel ratio control.
The ECM continuously monitors the heated oxygen sensor output voltage while the engine is running. The Diagnostic Trouble Code (DTC) P0138 is stored if the heated oxygen sensor voltage output is 1.2 V or higher for 10 seconds or more.
What are the Possible Causes of the DTC P0138 2018 Toyota RAV4?
- Faulty Oxygen Sensor Bank 1 Sensor 2
- Oxygen Sensor Bank 1 Sensor 2 harness is open or shorted
- Oxygen Sensor Bank 1 Sensor 2 circuit poor electrical connection
- Gas leak from exhaust system
How to Fix the DTC P0138 2018 Toyota RAV4?
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.
Code Tech Notes
What is the Cost to Diagnose the Code?
Labor: 1.0
To diagnose the P0138 2018 Toyota RAV4 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.
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Frequently Asked Questions about P0138 2018 Toyota RAV4 Code
1. What does the OBDII code P0138 mean on a 2018 Toyota RAV4?
P0138 indicates that the oxygen sensor on Bank 1 Sensor 2 is detecting a voltage higher than the expected range, suggesting a potential issue in the sensor circuit or related components.
2. What are the symptoms of code P0138 in a 2018 Toyota RAV4?
Common symptoms include the check engine light turning on, poor fuel economy, rough idling, or a noticeable drop in engine performance.
3. What causes the P0138 code on a 2018 Toyota RAV4?
Possible causes include a faulty oxygen sensor (Bank 1 Sensor 2), damaged wiring or connections in the sensor circuit, a short to voltage, or issues with the vehicle's catalytic converter.
4. Can a faulty oxygen sensor trigger the P0138 code on a Toyota RAV4?
Yes, a malfunctioning oxygen sensor is one of the most common reasons for code P0138 to appear.
5. How do I diagnose the P0138 code on my 2018 Toyota RAV4?
Start by inspecting the wiring and connectors for damage or corrosion, then test the oxygen sensor for proper voltage readings using a multimeter. A scan tool can also help monitor live data.
6. Can I drive my 2018 Toyota RAV4 with the P0138 code?
Driving with this code is not recommended, as it can lead to increased emissions, reduced fuel efficiency, and potential damage to the catalytic converter.
7. How much does it cost to fix the P0138 code on a Toyota RAV4?
The repair cost depends on the root cause. Replacing an oxygen sensor typically costs $150-$300, while wiring repairs or catalytic converter replacements can be more expensive.
8. Does a dirty air filter cause the P0138 code on a 2018 Toyota RAV4?
No, a dirty air filter is unlikely to cause this code. P0138 is specifically related to the oxygen sensor circuit and its voltage readings.
9. How do I reset the P0138 code on my 2018 Toyota RAV4?
After fixing the issue, you can reset the code using an OBDII scanner, or it may clear itself after several drive cycles if the problem is resolved.
10. Could a bad catalytic converter cause the P0138 code on a Toyota RAV4?
Yes, a failing catalytic converter can lead to abnormal oxygen sensor readings, which may trigger the P0138 code.
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