AutoCodes – GMC – P0446 2018 GMC Sierra

P0446 2018 GMC Sierra Code - Evaporative Emission Vent System Performance

Quick Answer

This Diagnostic Trouble Code (DTC) tests the Evaporative Emission (EVAP) system for a restricted or blocked EVAP vent path that would cause excess amounts of vacuum to be developed in the EVAP system. Common causes include Plugged vapor canister, Pinched or blocked EVAP hose, Faulty Evaporative Emission Vent Solenoid Valve. Severity is Low - monitor the vehicle and repair when practical. The vehicle can usually be driven if no severe symptoms are present, but symptoms should be checked before extended driving.

What it means: P0446 2018 GMC Sierra indicates Evaporative Emission Vent System Performance.
Common causes: Common causes include Plugged vapor canister, Pinched or blocked EVAP hose, Faulty Evaporative Emission Vent Solenoid Valve.
Severity: Low - monitor the vehicle and repair when practical.
Can I drive?: The vehicle can usually be driven if no severe symptoms are present, but symptoms should be checked before extended driving.

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Code Popularity 575

How popular is this code, among other codes? Low

Repair Importance Level

Low (Monitor) (1 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

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

Description
Step-by-Step Diagnostic Guide
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
FAQs
Comments
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Code P0446 2018 GMC Sierra Description

This Diagnostic Trouble Code (DTC) tests the Evaporative Emission (EVAP) system for a restricted or blocked EVAP vent path that would cause excess amounts of vacuum to be developed in the EVAP system. The Engine Control Module (ECM) commands the EVAP purge solenoid valve Open and the EVAP vent solenoid valve Closed. This allows vacuum to be applied to the EVAP system. Once a calibrated vacuum level has been reached, the ECM commands the EVAP purge solenoid valve Closed and the EVAP vent solenoid valve Open. The ECM monitors the Fuel Tank Pressure (FTP) sensor for a decrease in vacuum. If the vacuum does not decrease to near 0 in H2O in a calibrated time, this DTC sets.

OBDII Code P0446 2018 GMC Sierra - Evaporative Emission Vent System Performance - AutoCodes.com — P0446 2018 GMC Sierra Code - Evaporative Emission Vent System Performance

What does this mean?

What are the Possible Causes of the DTC P0446 2018 GMC Sierra?

Plugged vapor canister
Pinched or blocked EVAP hose
Faulty Evaporative Emission Vent Solenoid Valve
Evaporative Emission Vent Solenoid Valve harness is open or shorted
Evaporative Emission Vent Solenoid Valve circuit poor electrical connection
Faulty Fuel Tank Pressure (FTP) sensor

How to Fix the DTC P0446 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 does this mean?

Code Tech Notes

Dirt and dust intrusion into the EVAP canister vent hose assembly, resulting in restricted air flow, may cause this condition.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0446 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 P0446 2018 GMC Sierra 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 P0446 2018 GMC Sierra Code

1. What does OBDII code P0446 on a 2018 GMC Sierra indicate?

The P0446 code specifically relates to the evaporative emission vent system performance.

2. What are common symptoms of a P0446 code in a 2018 GMC Sierra?

Common symptoms include the check engine light illuminating on the dashboard and potential issues with the vehicle's fuel economy.

3. What are the possible causes of a P0446 code in a 2018 GMC Sierra?

Potential causes include a faulty vent valve, a blocked vent valve, damaged vent hoses, or issues with the charcoal canister.

4. How can I diagnose the source of a P0446 code in my 2018 GMC Sierra?

Diagnosing the issue typically involves inspecting the vent valve, checking for blockages in the vent system, and testing the functionality of the charcoal canister.

5. Can a P0446 code in a 2018 GMC Sierra cause any other problems besides the check engine light?

While the code itself may not directly cause drivability issues, ignoring it can lead to increased emissions and potential long-term damage to the vehicle's emission control system.

6. How can I repair a P0446 code in my 2018 GMC Sierra?

Repairing a P0446 code may involve replacing the vent valve, clearing any blockages in the vent system, repairing or replacing damaged hoses, or addressing issues with the charcoal canister.

7. Is it safe to continue driving my 2018 GMC Sierra with a P0446 code?

While driving with a P0446 code may not immediately harm your vehicle, it's advisable to address the issue promptly to ensure optimal performance and emissions compliance.

8. Can I reset the check engine light after fixing a P0446 code on my 2018 GMC Sierra?

Once the underlying issue causing the P0446 code is resolved, you can typically reset the check engine light using an OBDII scanner or by disconnecting the vehicle's battery for a few minutes.

9. How long does it usually take to repair a P0446 code in a 2018 GMC Sierra?

The repair time for a P0446 code can vary depending on the specific cause of the issue, but it typically takes a few hours to diagnose and address the problem effectively.

10. Should I seek professional help to fix a P0446 code in my 2018 GMC Sierra?

If you are not experienced with automotive repairs or lack the necessary tools, it's recommended to consult a qualified mechanic or dealership to diagnose and repair a P0446 code for optimal results.