P0440

DTC P0440 EVAP Control System Malfunction

Circuit Description
The evaporative system includes the following components:
- Fuel tank
- EVAP vent solenoid
- Fuel tank pressure sensor
- Fuel pipes and hoses
- Fuel vapor lines
- Fuel cap
- EVAP canister
- Purge lines
- EVAP canister purge valve EVAP service port

The evaporative emission system is checked by applying vacuum to the EVAP system and monitoring for a vacuum decay. The PCM monitors the vacuum level through the fuel tank pressure sensor signal.

At an appropriate time, the EVAP canister purge valve and the EVAP vent solenoid are turned ON, allowing the engine to draw a small vacuum on the entire evaporative emission system. After the desired vacuum level has been achieved, the EVAP canister purge valve is turned OFF, sealing the system. If a sufficient vacuum level cannot be achieved, a large leak is indicated. This can be caused by the following conditions:
- Missing or faulty fuel cap
- Disconnected or faulty fuel tank pressure sensor
- Disconnected, damaged, pinched, or blocked fuel tank vapor line
- Disconnected or faulty EVAP canister purge valve
- Disconnected or faulty EVAP vent solenoid
- Open ignition feed circuit to the EVAP vent or purge solenoid
- Damaged EVAP canister
- Leaking fuel sender assembly O-ring
- Leaking fuel tank or fuel filler neck

Any of the above conditions can set a Diagnostic Trouble Code P0440. DTC P0440 is a type A code.

Conditions for Setting the DTC
- Diagnostic Trouble Codes P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0125, P0131, P0132, P0133, P0134 and P1133 not set.
- The BARO is greater than 72.3 kPa.
- IAT and ECT are between 3.5 °C (38.5 °F) and 90.5 °F at engine start up.
- The difference between IAT and ECT at start up is less than 6.75 °C (12.2 °F).
- The Vehicle Speed is less than 98 kph (60 mph).
- The Fuel Tank Level Sensor reads between 10 % and 90 %.
- Fuel Level counts vary by less than 15 counts in a 0.125 second time frame.
- Maximum Engine Run time is at least 540 seconds.
- The difference between the actual Fuel Tank Pressure and the expected Fuel Tank Pressure is less than the PCM's expectations.

The above conditions are met, and the following condition is met once:
- The EVAP system is unable to achieve or maintain vacuum during the diagnostic test. The amount of decay will vary with the fuel level.

Action Taken When the DTC Sets
- The Malfunction Indicator Lamp (MIL) will illuminate.
- The PCM will disable the EVAP purge vale solenoid.
- The PCM will record operating conditions at the time the diagnostic fails. The Freeze Frame and Failure Records buffers will store this information.
- A history Diagnostic Trouble Code is stored.

Conditions for Clearing the MIL/DTC
- The MIL will turn OFF after one ignition cycle in which the diagnostic runs without a fault.
- Freeze Frame information and the history Diagnostic Trouble Code will clear after one ignition cycle in which the diagnostic runs without a fault.
- Diagnostic Trouble Codes can be cleared with the Scan Tool's "Clear Info" function.

Diagnostic Aids
Check for the following conditions:
- A missing, loose, or damaged fuel cap.
- Missing or damaged O-rings at the EVAP canister fuel vapor fittings and the purge line fittings.
- A cracked EVAP canister.
- Damaged or disconnected source vacuum line. EVAP purge line, vent hose or fuel tank vapor line.
- The Fuel Pressure Sensor shares a 5 Volt reference with the MAP sensor and TP sensor.

If these codes are also set, it could indicate a problem with the 5 Volt reference circuit or components itself.
- The Fuel Pressure Sensor share a ground with the MAP sensor and the TP sensor.
- A poor connection at the PCM: Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals.
- Damaged harness: Inspect the wiring harness to the EVAP vent solenoid, the EVAP purge solenoid, and the fuel tank pressure sensor for shorts to ground, shorts to battery positive and open circuits.
- A kinked, pinched or plugged vacuum source, EVAP purge, or fuel tank vapor line. Verify that the lines are not restricted.

Check for charcoal particles. Refer to EVAP System before starting repairs.

Reviewing the Fail Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the Diagnostic Trouble Code to set occurs. This may assist in diagnosing the condition.

Step 1:

Steps 2 - 7:

Steps 8 - 9:

Steps 10 - 12:

Steps 13 - 15:

Steps 16 - 19:

Step 20:

Test Description
Number(s) below refer to the step number(s) on the Diagnostic Chart:
1. The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame and failure records data on the Tech 2 if applicable. This creates an electronic copy of the data taken when the malfunction occurred. The information is then stored on the Tech 2 for later reference.
4. If a vent solenoid or EVAP canister purge valve electrical malfunction is present, the purge system will not operate correctly. Repairing the electrical malfunction will very likely correct the condition that set Diagnostic Trouble Code P0440.
5. Check the fuel tank pressure sensor at ambient pressure.
7. Forces the fuel tank pressure sensor to re-zero.
8. Determines whether or not the EVAP system is sealed sufficiently to be pressurized. If not, the large leak must be located and corrected before continuing with diagnosis.
9. Verifies that the fuel tank pressure sensor accurately reacts to EVAP system pressure changes.
12. Ensures that sufficient source vacuum is present at the EVAP canister purge valve.
13. Check for a stuck closed EVAP canister purge valve.
20. Insures proper system integrity.