AutoCodes – GMC – P0442 2017 GMC Sierra

P0442 2017 GMC Sierra Code - Evaporative Emission System Small Leak Detected

Quick Answer

The engine off natural vacuum test is the small leak detection diagnostic for the evaporative emission system. Common causes include Missing or loose fuel cap, Incorrect fuel filler cap used, Fuel filler cap remains open or fails to close. 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: P0442 2017 GMC Sierra indicates Evaporative Emission System Small Leak Detected.
Common causes: Common causes include Missing or loose fuel cap, Incorrect fuel filler cap used, Fuel filler cap remains open or fails to close.
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 444

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 Jun 27, 2022

Description
Step-by-Step Diagnostic Guide
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
Comments
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Code P0442 2017 GMC Sierra Description

The engine off natural vacuum test is the small leak detection diagnostic for the evaporative emission system. This diagnostic tests the Evaporative Emission (EVAP) system for a small leak when the key is turned OFF and the correct conditions are met. The heat from the exhaust system is transferred into the fuel tank while the vehicle is operating. Prior to running this test fuel volatility is analyzed and then factored into this test. When the vehicle is turned OFF and the EVAP system has sealed a change in the fuel tank vapor temperature occurs which results in a corresponding pressure change in the fuel tank vapor space. This change is monitored by the Engine Control Module (ECM) using the Fuel Tank Pressure (FTP) sensor input. With a leak in the system, the amount of pressure change will be less than that of a sealed system. The Diagnostic Trouble Code (DTC) will be set when the ECM detects a leak in the EVAP system that is greater than a calibrated amount.

OBDII Code P0442 2017 GMC Sierra - Evaporative Emission System Small Leak Detected - AutoCodes.com — P0442 2017 GMC Sierra Code - Evaporative Emission System Small Leak Detected

What does this mean?

What are the Possible Causes of the DTC P0442 2017 GMC Sierra?

Missing or loose fuel cap
Incorrect fuel filler cap used
Fuel filler cap remains open or fails to close
Foreign matter caught in fuel filler cap
Leaking EVAP Canister
Leaking EVAP System Hose
Leaking Fuel Tank
Faulty Fuel Tank Pressure Sensor

How to Fix the DTC P0442 2017 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

The P0442 code means that the control module has detected a small leak in the Evaporative Emission (EVAP). A loose fuel tank filler cap is the most common cause that will trigger the P0442 code.

There is a factory service bulletin for all the models from 2000 through 2021. The factory states that there are seven critical connections that could likely lead to this DTC being set:
1. Purge tube to purge valve (at intake manifold)
2. Purge tube to chassis EVAP line (at the rear of the engine, near transmission)
3. Chassis EVAP line to canister (at canister)
4. Fuel tank load line to canister (at canister)
5. Vent valve line to vent valve (at vent valve)
6. Fuel tank load line jumper connection (near fuel tank)
7. Fuel tank cap is closed properly (at refuel compartment)

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0442 2017 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 P0442 2017 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.