AutoCodes – Toyota – P2251 Toyota

P2251 Toyota 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 Toyota 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.

Save to My Repairs My Repairs

AI answers can be wrong. Verify repairs with testing. Open full chat

Code Popularity 4,131

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
Comments
Add Comment

💬 Need more help? Ask Coddy for instant answers — it's free!

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

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 Toyota?

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 Toyota 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 P2251 Toyota code?

Need more information on how to fix the P2251 Toyota code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P2251 Toyota code diagnosed by a professional: Find a repair shop in your area

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.