P0440

DTC P0440 Evaporative Emission System Large Leak/Low Tank Vacuum

Circuit Description
The evaporative emission (EVAP) 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 EVAP system is checked by applying vacuum to the EVAP system and monitoring for a vacuum decay. The engine control module (ECM) monitors the vacuum level through the fuel tank pressure sensor signal. At the 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 EVAP 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 EVAP purge 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 beck.

Any of the above conditions can set Diagnostic Trouble Code (DTC) P0440.

The test is failed if the tank vacuum is less than 10 in H2O for 15 seconds and the manifold vacuum integral is greater than 49152 (proportional to purge mass from the tank).

Conditions for Setting the DTC
- DTC(s) P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0131, P0132, P0133, P0134, P0135, P0137, P0138, P0140, P0141, P0201, P0202, P0203, P0204, P0300, P0402, P0404, P0405, P0406, P0443, P0449, P0452, P0453, P0506, P0507, P1130, P1133, P1134, P1627, P1640 will not set.
- Engine Coolant Temperature (ECT) and Intake Air Temperature (IAT) are between 4 °C (40 °F) and 32 °C (90 °F) at engine start up.
- Intake Air Temperature (IAT) is not more than 6.25 °C (43.3 °F) greater than the ECT at engine start up.
- Engine Coolant Temperature (ECT) is net more than 6.25 °C (43.3 ° F) greater than Intake Air Temperature (IAT) at engine start up.
- Barometric Pressure (BARO) is greater than 72.3 kPa.
- Vehicle speed is less than or equal to 144.8 kph (90 mph).
- Fuel tank level is between 10% and 90%.
- The Throttle Position (TP) sensor is less than or equal to 100%.
- No fuel slosh, and the change in fuel level percent is 21 counts in 0.125 sec.
- Manifold vacuum is greater than or equal to 10 kPa.
- Fuel level is between 15% and 85%.
- System voltage is between 11 v and 16 v.
- The EVAP system is unable to achieve or maintain vacuum during the diagnostic test. The amount of decay will vary within the fuel level.

Action Taken When the DTC Sets
- The Malfunction Indicator Lamp (MIL) will illuminate.
- The ECM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records buffers.
- A history DTC is stored.
- Coolant fan turns on.

Conditions for Clearing the MIL/DTC
- The MIL will turn off after three consecutive ignition cycles in which the diagnostic runs without a fault.
- A history DTC will clear after 40 consecutive warm-up cycles without a fault.
- DTC(s) can be cleared with battery disconnect.

Diagnostic Aids
Although this DTC is considered a type A diagnostic, it acts like a type B diagnostic under certain conditions. Whenever this diagnostic reports the system has passed, or if the battery is disconnected, the diagnostic must fail twice before setting a DTC. The initial failure is not reported to the diagnostic executive or displayed on a scan tool. A passing system always reports to the diagnostic executive immediately.

Check for the following conditions:
- Missing or damaged fuel cap.
- Missing or damaged O-rings at fuel vapor and EVAP purge line canister fittings.
- Cracked or punctured EVAP canister.
- Damaged source vacuum line, EVAP purge line, EVAP vent hose or fuel lank vapor line.
- Poor connection at the ECM. Inspect the harness connectors for the following conditions:
- Backed-out terminals
- Improper mating
- Broken locks
- Improperly formed
- Damaged terminals
- Poor terminal-to-wire connection

- Damaged harness. Inspect the wiring harness to the EVAP vent solenoid, EVAP canister purge valve, and the fuel tank pressure sensor for an intermittent open or short circuit.
- Kinked, pinched or plugged vacuum source, EVAP purge, or fuel tank vapor line. Verify that the lines are not restricted.

Steps 1 - 6:

Steps 7 - 11:

Steps 12 - 19:

Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
1. The On-Board Diagnostic (OBD II) System Check prompts the technician to complete some basic checks and store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data taken when the malfunction occurred. The information is then stored on the scan tool for later reference.
3. If a vent solenoid or EVAP canister purge valve electrical malfunction is present, the purge system will not operate correctly.
4. Checks the fuel tank pressure sensor at ambient pressure.
6. Forces fuel tank pressure sensor to re-zero.
7. 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.
8. Verifies that the fuel tank pressure sensor accurately reacts to EVAP system pressure changes.
11. Ensures that sufficient source vacuum is present at the EVAP canister purge valve.
12. Checks for a stuck, closed EVAP canister purge valve
19. Insures proper system integrity.