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Engine-Codes – GMC – P0442 2018 GMC Sierra

P0442 2018 GMC Sierra Code - Evaporative Emission System Small Leak Detected

Quick Answer

The P0442 code for a 2018 GMC Sierra indicates that there is a small leak detected in the evaporative emission system. Common causes include Loose or damaged gas cap, Cracked or damaged hoses in the evaporative emission system, Faulty purge 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
P0442 2018 GMC Sierra indicates Evaporative Emission System Small Leak Detected.
Common causes
Common causes include Loose or damaged gas cap, Cracked or damaged hoses in the evaporative emission system, Faulty purge 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.
What is this?
Table of contents Created and updated by William Orellana on Sep 10, 2024
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Code P0442 2018 GMC Sierra Description

The P0442 code for a 2018 GMC Sierra indicates that there is a small leak detected in the evaporative emission system. The evaporative emission system is responsible for capturing and storing fuel vapors from the fuel tank to prevent them from escaping into the atmosphere. A small leak in this system can lead to increased emissions, reduced fuel efficiency, and potential performance issues in the vehicle.

OBDII Code P0442 2018 GMC Sierra - Evaporative Emission System Small Leak Detected
P0442 2018 GMC Sierra Code - Evaporative Emission System Small Leak Detected

Common Causes of P0442 2018 GMC Sierra

  1. Loose or damaged gas cap
  2. Cracked or damaged hoses in the evaporative emission system
  3. Faulty purge valve
  4. Leaking fuel tank
  5. Malfunctioning charcoal canister

Symptoms of P0442 2018 GMC Sierra

  1. Check Engine Light is illuminated
  2. Strong fuel odor near the vehicle
  3. Decreased fuel efficiency
  4. Rough idle or stalling
  5. Difficulty starting the engine

How to Fix P0442 2018 GMC Sierra

  1. Inspect the gas cap for any signs of damage or wear. Replace if necessary.
  2. Check all hoses and connections in the evaporative emission system for leaks or cracks. Repair or replace as needed.
  3. Test the purge valve to ensure it is functioning properly. Replace if faulty.
  4. Inspect the fuel tank for any leaks or damage. Repair or replace as necessary.
  5. Check the charcoal canister for leaks or damage. Replace if needed.

Cost to Fix P0442 2018 GMC Sierra

The cost of repairing a P0442 code on a 2018 GMC Sierra can vary depending on the specific cause of the issue and the labor rates in your area. On average, the cost of parts for this repair can range from $50 to $200, with labor costs adding an additional $100 to $200. This means that the total cost for resolving a P0442 code could fall between $150 and $400. However, it's important to note that these are rough estimates, and the actual cost may differ based on various factors. It is advisable to consult with a certified mechanic or auto repair shop for a more accurate cost estimate based on your specific situation.

What does this mean?

Tech Notes for P0442 2018 GMC Sierra

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)

Need more information about the P0442 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.

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