AutoCodes – GMC – P257F 2018 GMC Sierra

P257F 2018 GMC Sierra Code - Engine Hood Switch Circuit High Voltage

Quick Answer

The Engine Control Module (ECM) applies 5 V to the hood ajar signal circuit and monitors the voltage to determine the position of the hood. Common causes include Faulty Hood Ajar Switch, Hood Ajar Switch harness is open or shorted, Hood Ajar 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: P257F 2018 GMC Sierra indicates Engine Hood Switch Circuit High Voltage.
Common causes: Common causes include Faulty Hood Ajar Switch, Hood Ajar Switch harness is open or shorted, Hood Ajar 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 451

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on Sep 21, 2022

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P257F 2018 GMC Sierra Description

The Engine Control Module (ECM) applies 5 V to the hood ajar signal circuit and monitors the voltage to determine the position of the hood. The hood ajar switch contains a multiplexed resistor. This resistor will vary the voltage seen by the Engine Control Module by pulling down the applied voltage based on the position of the switch. The Diagnostic Trouble Code (DTC) will be set when the Engine Control Module detects a short to voltage or an open/high resistance in the hood ajar signal input to the Engine Control Module.

OBDII Code P257F 2018 GMC Sierra - Engine Hood Switch Circuit High Voltage - AutoCodes.com — P257F 2018 GMC Sierra Code - Engine Hood Switch Circuit High Voltage

What does this mean?

What are the Possible Causes of the DTC P257F 2018 GMC Sierra?

Faulty Hood Ajar Switch
Hood Ajar Switch harness is open or shorted
Hood Ajar Switch circuit poor electrical connection
Faulty Engine Control Module (ECM)

How to Fix the DTC P257F 2018 GMC Sierra?

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 P257F 2018 GMC Sierra 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 P257F 2018 GMC Sierra 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 P257F 2018 GMC Sierra Code

1. What are the common symptoms of OBDII code P257F in a 2018 GMC Sierra?

- Common symptoms include illuminated Check Engine Light, issues with the hood latch operation, and possible intermittent starting problems.

2. What could cause the Engine Hood Switch Circuit High Voltage code (P257F) in a 2018 GMC Sierra?

- Possible causes include a faulty hood switch, damaged wiring in the hood switch circuit, or a malfunctioning body control module.

3. How can I diagnose the Engine Hood Switch Circuit High Voltage code P257F in my 2018 GMC Sierra?

- Diagnosis involves checking the hood switch for proper operation, inspecting the wiring for any damage or corrosion, and using a scan tool to retrieve trouble codes.

4. Can I drive my 2018 GMC Sierra with the P257F trouble code?

- It is generally safe to drive the vehicle with this code, but it is recommended to address the issue promptly to prevent any potential starting or electrical problems.

5. How do I repair the Engine Hood Switch Circuit High Voltage code P257F in my 2018 GMC Sierra?

- Repair may involve replacing the hood switch if faulty, repairing damaged wiring, or reprogramming the body control module. Consult a professional if needed.

6. Are there any DIY tips for fixing the P257F OBDII code in a 2018 GMC Sierra?

- DIY enthusiasts can start by checking the hood switch and its wiring for any visible issues or loose connections before seeking professional assistance.

7. Will resetting the trouble codes make the P257F code go away in my 2018 GMC Sierra?

- Resetting the codes may temporarily turn off the Check Engine Light, but if the underlying issue causing the P257F code is not fixed, the code will likely return.

8. Is the Engine Hood Switch Circuit High Voltage code P257F a common problem in 2018 GMC Sierras?

- While not extremely common, issues with the hood switch circuit causing the P257F code can occur in some 2018 GMC Sierra vehicles.

9. Can extreme weather conditions affect the likelihood of triggering the P257F trouble code in a 2018 GMC Sierra?

- Extreme weather conditions, particularly excessive heat or moisture, can potentially impact the hood switch operation and contribute to the P257F trouble code.

10. How long does it typically take to repair the P257F OBDII code in a 2018 GMC Sierra?

- The repair time can vary depending on the exact cause of the code and the complexity of the repair needed, but it may take a few hours to a day in most cases.