P0440

Engine Controls Schematics: MAF Sensor, EVAP System, EGR Valve:

SYSTEM DESCRIPTION
The EVAP LARGE LEAK TEST Is based on applying vacuum to the EVAP system and monitoring vacuum decay. The PCM monitors vacuum level via the fuel tank pressure sensor input. At an appropriate time, the EVAP canister purge valve and the EVAP vent valve/solenoid are turned on, allowing engine vacuum to draw a small vacuum on the entire evaporative emission system. If a sufficient vacuum level cannot be achieved, a large leak or a faulty EVAP canister purge valve is indicated. This can be caused by the following conditions:
^ Disconnected or faulty fuel tank pressure sensor
^ Missing, not completely installed or faulty fuel fill cap
^ Disconnected, damaged, pinched, or blocked EVAP purge line
^ Disconnected or damaged EVAP vent hose
^ Disconnected, damaged, pinched, or blocked fuel tank vapor line
^ Disconnected or faulty EVAP canister purge valve
^ Disconnected or faulty EVAP vent valve
^ Open ignition feed circuit to the EVAP vent or purge valve
^ Damaged EVAP canister
^ Leaking fuel sender assembly O-ring
^ Leaking fuel tank or fuel filler neck

Any of the above conditions can set DTC P0440.

CONDITIONS FOR RUNNING THE DTC
^ No TP sensor, ODM, IAT sensor, or MAP sensor DTCs set.
^ System voltage is between 9 and 16 volts.
^ Startup engine coolant temperature is between 4°C and 30°C (40°F and 86°F).
^ Startup engine coolant temperature is not more than 8°C (14°F) greater than startup intake air temperature.
^ Startup Intake air temperature is between 4°C and 30°C (40°F and 86°F).
^ Startup intake air temperature not more than 2°C (4°F) greater than start-up engine coolant temperature.
^ Fuel tank level is between 15 percent and 85 percent.
^ BARO is more than 75 kPa.

CONDITIONS FOR SETTING THE DTC
The EVAP system is not able to achieve or maintain vacuum during the diagnostic test.

ACTION TAKEN WHEN THE DTC SETS
^ The PCM will illuminate the MIL during the first trip in which the diagnostic runs and fails.
^ If equipped with traction control, the PCM will command the EBTCM via the serial data circuit to turn OFF traction control and illuminate the TRACTION OFF lamp.
^ The PCM will store conditions which were present when the DTC set as Freeze Frame/Failure Records data.

IMPORTANT: Although this diagnostic is considered type A, it acts like a type B diagnostic. Whenever the EVAP diagnostics report that a system has passed, or if the battery has been disconnected, the diagnostic must fail during 2 consecutive cold start trips 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.

CONDITIONS FOR CLEARING THE MIL/DTC
^ The PCM will turn the MIL OFF during the third consecutive trip in which the diagnostic has been run and passed.
^ The History DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.
^ The DTC can be cleared by using a scan tool.

DIAGNOSTIC AIDS
Inspect for the following:
^ Cracked or punctured EVAP canister.
^ Damaged or disconnected source vacuum line, EVAP purge line, vent hose or fuel tank vapor line.
^ Poor connection at the PCM.
^ Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection.
^ Damaged harness. Inspect the wiring harness to the EVAP vent valve, the EVAP 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.
^ Use the following procedure to test for a carbon release condition that could plug the system.
1. Turn off the ignition switch.
2. Remove the EVAP canister purge valve.
3. Lightly tap the canister purge valve on a clean work area looking for carbon particles exiting either of the vacuum ports.
4. If no carbon release is evident, reinstall the components and continue with the DTC P0440 diagnostic table. If carbon is being released from either component, continue with this service procedure.
5. Remove the charcoal canister from the vehicle.
6. Ensure that the main cylinder valve is turned off on the J41413 EVAP purge/pressure diagnostic station.
7. Disconnect the black hose that connects the nitrogen cylinder to the EVAP purge/pressure diagnostic station at the pressure regulator by unscrewing the knurled nut on the regulator. No tools are required to remove the black hose from the regulator.
8. Using a section of vacuum line, connect one end over the open threaded fitting of the EVAP purge/pressure diagnostic station pressure regulator.
9. Connect the remaining end to the purge valve end of the EVAP purge line at the vehicle and turn on the main nitrogen cylinder valve. Continue to blow any debris from the purge line for 15 seconds.
10. Return the EVAP pressure/purge diagnostic station to its original condition by reinstalling the black hose that was disconnected in step 7.
11. Replace the following components:
^ The EVAP canister purge valve.
^ The EVAP canister.
12. Proceed with the DTC P0440 diagnostic table. Reviewing the Fail Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition.

TEST DESCRIPTION

Steps 1 - 5:

Steps 6 - 12:

Steps 13 - 21:

The numbers below refer to the step numbers on the diagnostic table:
1. The Powertrain On-Board Diagnostic (OBD) System Check prompts you to complete some of the basic checks and store the Freeze Frame and Failure records data on the scan tool if applicable.
2. If a vent valve or EVAP purge valve electrical malfunction is present, the purge system will not operate correctly. Repairing the electrical malfunction that caused the additional DTC to set will very likely correct the condition that set this DTC.
3. Inspects for a fuel tank pressure sensor stuck high condition. The fuel tank pressure must be relieved by removing the canister line from the fuel tank or EVAP canister. The fuel fill cap will not relieve the fuel tank pressure due to a check valve in the filler neck. The check valve seals when pressure is applied to prevent vapors from escaping through the filler neck. The scan tool should read within 1.0 inch H2O of the specified value.
4. Inspects for a large leak in the EVAP system.
5. Verifies that the fuel tank pressure sensor accurately reacts to EVAP system pressure changes. The EVAP station is pressurizing a sensor that normally reads vacuum. The scan tool reads high pressure at 0 volts and high vacuum at 5 volts. The scan tool can only read a max pressure of 6.0 inches of H2O (0 volts), however the EVAP service station can pressurize the system to much higher pressures. The scan tool value should be within 0.5 inch H2O of the specified value.
6. Inspects for a leaking EVAP canister line, or vent valve.
8. Inspects for a stuck closed or plugged EVAP canister purge valve.
9. Inspects for a leaking or stuck open EVAP canister purge valve, the scan tool should read within 1.0 inch HG of the specified value.
12. Inspects for a leaking or stuck open EVAP canister purge valve. The valve should be within 1.0 in HG of the specified value.
14. Inspects for a plugged EVAP system.
18. Ensures that sufficient source vacuum is present at the EVAP canister purge valve.
21. The EVAP station is pressurizing a sensor that normally reads vacuum. The scan tool reads high pressure at 0 volts and high vacuum at 5 volts. The scan tool can only read a max pressure of 6.0 inches of H2O (0 volts), however the EVAP service station can pressurize the system to much higher pressures. The scan tool value should be within 0.5 inch H2O of the specified value.