AutoCodes – Generic – P256B

P256B Code - Engine Idle Speed Selector Sensor/Switch Range/Performance

Quick Answer

The Engine Control Module (ECM) monitors the Engine Idle Speed Selector Sensor/Switch circuit signal. Common causes include Faulty Engine Idle Speed Selector Sensor/Switch, Engine Idle Speed Selector Sensor/Switch harness is open or shorted, Engine Idle Speed Selector Sensor/Switch circuit poor electrical connection. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means: P256B indicates Engine Idle Speed Selector Sensor/Switch Range/Performance.
Common causes: Common causes include Faulty Engine Idle Speed Selector Sensor/Switch, Engine Idle Speed Selector Sensor/Switch harness is open or shorted, Engine Idle Speed Selector Sensor/Switch circuit poor electrical connection.
Severity: High - diagnose this code as soon as possible.
Can I drive?: Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

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Code Popularity 4,578

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Intermediate (2 / 3)

What is this?

Table of contents Created and updated by William Orellana on Jan 19, 2019

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P256B Description

The Engine Control Module (ECM) monitors the Engine Idle Speed Selector Sensor/Switch circuit signal. The ECM set the OBDII code when the Engine Idle Speed Selector Sensor/Switch signal is out of factory specifications.

OBDII Code P256B - Engine Idle Speed Selector Sensor/Switch Range/Performance - AutoCodes.com — P256B Code - Engine Idle Speed Selector Sensor/Switch Range/Performance

What does this mean?

What are the Possible Causes of the DTC P256B?

Faulty Engine Idle Speed Selector Sensor/Switch
Engine Idle Speed Selector Sensor/Switch harness is open or shorted
Engine Idle Speed Selector Sensor/Switch circuit poor electrical connection

How to Fix the DTC P256B?

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 P256B 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 P256B code?

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Need Help with the 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 P256B Code

What does the OBDII code P256B mean?

P256B indicates an issue with the Engine Idle Speed Selector Sensor/Switch, specifically related to its performance or being out of its expected range.

What are the common symptoms of code P256B?

Symptoms may include an irregular or unstable idle speed, poor acceleration, increased fuel consumption, and an illuminated Check Engine Light.

What causes the P256B code to appear?

Common causes include a faulty idle speed selector sensor, damaged wiring or connectors, a malfunctioning engine control module (ECM), or sensor misalignment.

Can I drive my car with the P256B code?

Driving may be possible, but it is not recommended as it could lead to poor engine performance, increased emissions, or further damage to engine components.

How is code P256B diagnosed?

A technician will use a scan tool to verify the code, inspect the idle speed selector sensor and related wiring, and test for proper operation and voltage readings.

How do you fix the P256B code?

Repairs may include replacing the idle speed selector sensor, repairing damaged wiring or connectors, or updating or reprogramming the ECM if necessary.

How much does it typically cost to fix the P256B code?

Repair costs can range from $150 to $400, depending on whether the sensor, wiring, or ECM needs servicing or replacement.

Can a dirty throttle body cause the P256B code?

While not a direct cause, a dirty throttle body can contribute to idle issues, so it’s worth inspecting and cleaning if necessary.

Does resetting the Check Engine Light fix the P256B code?

Resetting the light may temporarily clear the code, but the underlying issue must be addressed to prevent the code from returning.

How can I prevent the P256B code from recurring?

Regular maintenance, inspecting sensors and wiring for damage, and addressing idle-related issues promptly can help prevent this code from appearing again.