AutoCodes – Lexus – P2251 Lexus

P2251 Lexus Code - Rear Air/Fuel Ratio Sensor Bank 1 Sensor 1 VS Line High Voltage

Quick Answer

The rear air/fuel ratio (A/F) sensor (bank 1, sensor 1) is installed in the exhaust manifold and detects oxygen content in the exhaust gas. Common causes include Rear Air/Fuel Ratio Sensor Bank 1 Sensor 1 harness is open or shorted, Rear Air/Fuel Ratio Sensor Bank 1 Sensor 1 circuit poor electrical connection, Faulty Rear Air/Fuel Ratio Sensor Bank 1 Sensor 1. 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: P2251 Lexus indicates Rear Air/Fuel Ratio Sensor Bank 1 Sensor 1 VS Line High Voltage.
Common causes: Common causes include Rear Air/Fuel Ratio Sensor Bank 1 Sensor 1 harness is open or shorted, Rear Air/Fuel Ratio Sensor Bank 1 Sensor 1 circuit poor electrical connection, Faulty Rear Air/Fuel Ratio Sensor Bank 1 Sensor 1.
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 3,011

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
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P2251 Lexus Description

The rear air/fuel ratio (A/F) sensor (bank 1, sensor 1) is installed in the exhaust manifold and detects oxygen content in the exhaust gas. The rear A/F sensor transmits a signal to the Powertrain Control Module (PCM), and it enables overall feedback control. The PCM controls fuel injection duration by comparing the target air/fuel ratio with the rear A/F sensor signal. When the VSB1 terminal voltage is more than a specified value for a predetermined time, the PCM detects a malfunction and stores a DTC.

OBDII Code P2251 Lexus - Rear Air/Fuel Ratio Sensor Bank 1 Sensor 1 VS Line High Voltage - AutoCodes.com — P2251 Lexus Code - Rear Air/Fuel Ratio Sensor Bank 1 Sensor 1 VS Line High Voltage

What does this mean?

What are the Possible Causes of the DTC P2251 Lexus?

Rear Air/Fuel Ratio Sensor Bank 1 Sensor 1 harness is open or shorted
Rear Air/Fuel Ratio Sensor Bank 1 Sensor 1 circuit poor electrical connection
Faulty Rear Air/Fuel Ratio Sensor Bank 1 Sensor 1

How to Fix the DTC P2251 Lexus?

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 is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P2251 Lexus 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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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 P2251 Lexus Code

1. What does the OBDII code P2251 mean on a Lexus?

P2251 indicates an issue with the Rear Air/Fuel Ratio Sensor Bank 1 Sensor 1. Specifically, it means the Voltage Signal (VS) line is experiencing high voltage, which may disrupt proper sensor operation.

2. What are the common symptoms of code P2251 in a Lexus?

Symptoms may include poor fuel efficiency, rough idling, reduced engine performance, illuminated check engine light, and increased exhaust emissions.

3. What causes code P2251 to appear on a Lexus?

Common causes include a faulty air/fuel ratio sensor, damaged wiring or connectors, an exhaust leak, or issues with the engine control module (ECM).

4. How do you diagnose a P2251 code on a Lexus?

Technicians typically inspect the air/fuel sensor, wiring, and connectors for damage, check for exhaust leaks, and use a scan tool to monitor sensor voltage and ECM operation.

5. Can I drive my Lexus with a P2251 code?

While the car may still be drivable, driving with this code can lead to poor fuel economy, potential damage to the catalytic converter, and increased emissions. Itâ€™s best to address it promptly.

6. How can I fix the P2251 code on a Lexus?

Repairs may include replacing the faulty air/fuel ratio sensor, repairing or replacing damaged wiring or connectors, fixing exhaust leaks, or reprogramming or replacing the ECM if necessary.

7. How much does it cost to fix the P2251 code on a Lexus?

Repair costs vary depending on the issue but typically range from $200 to $400 for sensor replacement and labor. Extensive wiring or ECM repairs may cost more.

8. What tools are needed to troubleshoot the P2251 code?

Youâ€™ll need an OBDII scanner to read the code, a multimeter to test wiring and sensor voltage, and possibly tools to inspect and replace the air/fuel ratio sensor.

9. Is the P2251 code specific to Lexus vehicles?

No, P2251 is a generic OBDII code that can appear on other vehicles, but its exact meaning and repair process may vary depending on the make and model.

10. How can I prevent the P2251 code from occurring on my Lexus?

Regular maintenance, such as inspecting sensors, wiring, and exhaust components, and addressing issues like exhaust leaks promptly can help prevent this code.