Jeep Patriot P0440: Meaning, Causes, How to Fix

The P0440 code is a common trouble code that many Jeep Patriot owners may encounter. It indicates that there is an issue with the vehicle’s Evaporative Emission Control (EVAP) system. Specifically, the EVAP system is malfunctioning.

A variety of causes can trigger the P0440 code, with the most common one being a loose or damaged fuel tank filler cap.

P0440 is normally not an immediate threat to the driveability of your Patriot. Certainly, anytime the service engine soon light is on; it’s good to deal with it as soon as possible though.

Jeep Patriot P0440

Table of Contents

P0440 Code Definition

Evaporative Emission Control System – Malfunction

P0440 is a generic code, which means it has the same definition for the Jeep Patriot as it would any other vehicle made after the 1996 model year.

EVAP System

A loose or bad gas cap is the first thing you should check if your Patriot has P0440

The EVAP system is designed to capture, store, and recycle fuel vapors from the fuel tank and delivery system, preventing them from being released into the atmosphere.

Essential components of the system include fuel vapor hoses, a charcoal canister for fuel vapor storage, and computer-controlled purge and vent valves.

The EVAP system should not affect the way your Patriot’s engine runs whatsoever.

Control Malfunction

When the Patriot’s onboard diagnostics system (OBD-II) detects a fault in the EVAP system via a vacuum test, it generates the P0440 code.

This code is a general indication of a malfunction in the EVAP system and does not pinpoint the specific problem. It is common for another code from the P044X series to accompany the P0440 code, which can help provide further information on the issue.

If that’s the case for your Patriot, you may want to start your diagnosis with one of the other codes. Here are some of the common ones:

P0440 Symptoms

Jeep Patriot P0440 Symptoms

The P0440 code will typically not be accompanied by any noticeable symptoms other than the smell of gas and the service engine soon light. Fuel economy may suffer.

The area around the fuel tank may smell of gas. There could also be a fuel leak. Often, this code is easily remedied by a new gas cap.

The EVAP system deals directly with fuel vapors. If these vapors are leaking from the system, you’ll often smell them faintly while operating the vehicle. It may be more noticeable right after you fill up.

P0440 Causes: Jeep Patriot

Leaking Gas Cap

A common cause of the P0440 code in a Jeep Patriot is a leaking or loose gas cap.

Check the gas cap and ensure it is properly sealing the fuel tank, as this can lead to a malfunction with the Evaporative Emission Control System (EVAP).

Valves and Hoses

Another cause for the P0440 code could be leaking or damaged valves and hoses in the EVAP system. These components are responsible for capturing, storing, and recycling fuel vapors from the fuel tank and fuel delivery system.

Damaged or leaking hoses may lead to a small leak or even large leaks, resulting in a malfunction and triggering the P0440 code.

Evap Canister Issues

The EVAP canister itself may be the source of the problem if there is a leak or damage. The canister is designed to store fuel vapors and release them into the engine’s intake manifold to be burned during the combustion process.

Purge Solenoid Problems

P0440 fix Jeep Patriot
Purge valves come in many shapes and sizes

The P0440 code can also be attributed to purge solenoid issues within the EVAP system. The purge solenoid is responsible for controlling the flow of fuel vapors from the canister to the engine.

Malfunctioning solenoids can cause problems with the proper functioning of the EVAP system, leading to small or large leaks, a decrease in fuel efficiency, and less than optimal engine performance.

Other Causes

  • Damaged fuel tank: Physical damage or corrosion of the fuel tank can lead to leaks or other issues with the EVAP system, generating the P0440 code. A damaged fuel tank will need to be repaired or replaced.
  • Damaged fuel tank: Physical damage or corrosion of the fuel tank can lead to leaks or other issues with the EVAP system, generating the P0440 code. A damaged fuel tank will need to be repaired or replaced.
  • Fuel filler neck: There is often a gasket where the fuel filler neck connects with the gas tank. This gasket can dry out, especially with vehicles that spend their time in dry climates. When it dries out, the fuel tank can’t hold pressure anymore.

Diagnosing P0440 Code

Jeep Patriot P0440 Diagnosis

Using Smoke Test

A professional approach to diagnosing the P0440 code in a Jeep Patriot is by performing a smoke test.

This test involves filling the evaporative emission control system with smoke to identify possible leaks. The technician will visually inspect the system for areas where smoke is escaping, indicating the location of the leak.

To conduct a smoke test, the technician will typically begin by securing the gas cap and removing the EVAP Purge Control Valve.

After connecting a smoke machine to the system, the technician will monitor the smoke flow to pinpoint any leaks. In some cases, there may be multiple leaks or issues that require further attention.

Using an OBDII Scanner

An OBDII scanner is another valuable tool for diagnosing the P0440 code in a Jeep Patriot. By connecting the scanner to the vehicle’s diagnostic port, technicians can access related information about the evaporative emission control system and real-time sensor data.

As mentioned above, P0440 is often accompanied by other codes, which may provide more info as to what part of your Patriot’s EVAP system is malfunctioning.

Frequently Asked Questions

Can driving with a P0440 code damage my Jeep Patriot?

In most cases, driving with a P0440 code will not cause damage to your Jeep Patriot. The code indicates a problem with the evaporative emissions system, which can lead to decreased fuel efficiency and increased emissions output. However, it does not directly impact the engine’s performance or cause serious damage.

How much does it cost to fix P0440 code in Jeep Patriot?

The cost to fix a P0440 code in a Jeep Patriot can vary, depending on the specific issue and the required repairs. I

t could be as simple as replacing a loose or faulty gas cap, which would be relatively inexpensive. In other cases, the issue could be related to a more significant component, such as the EVAP system’s charcoal canister, purge valve, or vent solenoid.

These repairs may cost significantly more. To get an accurate estimate, consult a professional mechanic.

Yes, P0440, P0441, and P0446 codes are all related to the evaporative emission control system in a Jeep Patriot.

The P0440 code indicates a general issue with the system, while the P0441 code signals a problem with the EVAP system’s purge flow, and the P0446 code is related to vent control issues. While these codes are distinct, they all point to potential problems within the same emissions system.

If you encounter these codes, it is essential to have a professional mechanic diagnose and address the specific issue with your Jeep Patriot’s evaporative emissions system.