P0440
Circuit Description
The PCM tests the EVAP system for the following conditions:
^ Large and small leaks (P0440 and P0442)
^ Excess vacuum (P0446)
^ Purge flow during non-commanded conditions (P1441)
^ Fuel Pressure sensor and Fuel Level sensor faults (P0452, P0453, P0462 and P0463)
^ EVAP Purge and Vent Valve faults (P0443 and P0449)
The PCM monitors the amount of vacuum in the EVAP system by monitoring the Fuel Tank Pressure sensor. For this DTC the PCM turns ON both the EVAP Purge Valve and the EVAP Vent Valve when the Conditions for Running the DTC are met. This applies an engine vacuum to a closed EVAP system. This test checks whether a vacuum can develop in the EVAP system. Failure to develop a vacuum may result from a large leak or from a restriction. This DTC will set after two consecutive failures of the above test.
Conditions for Running the DTC
^ No misfire, fuel trim, injector control circuit, AIR, EGR, VSS, HO2S, TP, MAP, MAF, ECT or AT DTCs set.
^ Battery voltage is between 5 and 18 volts.
^ Barometric pressure is more than 75 kPa.
^ Fuel level is between 15% and 85% of full capacity for at least 10 seconds continuously. The time limit is required because fuel sloshing within the tank may cause the fuel level indication to vary outside the fuel level limits.
^ ECT at start up was between 4°C and 30°C (40°F and 86°F).
^ IAT at start up was between 4°C arid 30°C (40°F and 86°F).
^ ECT not more than 8°C above or 2°C below IAT at start up.
Conditions for Setting the DTC
The EVAP system cannot develop vacuum.
Action Taken When the DTC Sets
Important: Although these diagnostics are considered type A, they act like type B diagnostics under certain conditions. Whenever the EVAP diagnostics report that the system has passed, or if the battery has been disconnected, the diagnostic must fail during two 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.
^ The PCM will illuminate the MIL during the first trip in which the diagnostic test has been run and failed.
^ The PCM will store conditions which were present when the DTC set as Freeze Frame and Failure Records data.
Conditions for Clearing the MIL/DTC
^ The PCM turns the MIL Off as soon as proper tank vacuum is detected.
^ A last test failed (current DTC) clears when the diagnostic runs and does not fail.
^ A History DTC clears after forty consecutive warm-up cycles, if this or any Other emission related diagnostic does not report any failures.
^ Use a scan tool in order to clear the MIL/DTC.
^ Interrupting the PCM battery voltage may or may not clear DTCs. This practice is not recommended.
Diagnostic Aids
Notice: Use the Connector Test Adapter Kit J 35616-A for any test that requires probing the following items:
^ The PCM harness connectors
^ The electrical center fuse/relay cavities
^ The component terminals
^ The component harness connector
Using this kit will prevent damage caused by the improper probing of connector terminals.
Important: An accurate indication of fuel level is required for the PCM to properly Pass or Fail this DTC. Always diagnose fuel level sensor DTC's before performing this DTC's diagnostic table. Always check for fuel level sensor DTC's stored as History.
Perform a physical inspection of the EVAP system. Check for the following conditions:
^ A loose, missing, defective, or incorrect fuel tank cap
^ Incorrectly routed or defective EVAP system vacuum and vapor lines
^ A malfunctioning or damaged EVAP vapor canister
^ A vacuum leak between the Purge Solenoid Valve and the intake manifold.
Check for charcoal release from the EVAP vapor canister.
The vacuum and pressure in the EVAP system is measured in inches of H2O (water). Most gauges measure vacuum in inches of Hg (mercury) and pressure in psi (pounds per square inch). The following shows how the values compare:
Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
3. Inspect the service port. Make sure that the valve core is not loose or damaged (the valve core may have left hand threads). If service port leakage is suspected, use the following procedure:
Disconnect the purge line from the EVAP Purge valve.
Connect a hand vacuum pump to the service port. Connect the hose/adaptor over the unthreaded end portion of the service port only.
Apply vacuum to about 5 in. Hg. If the vacuum does not hold, replace the service port/pipe assy.
4. If the vehicle passes the Service Bay Test then an intermittent leak or restriction had occurred. Check for a loose or missing fuel tank cap that may have caused this DTC to set.
If the Service Bay Test can not be run, proceed to Step 5. If a fault is not currently present the diagnostic table steps will return you to Step 3.
10. Refer to the information supplied with the EVAP pressure/purge diagnostic cart on proper setup and adjustment procedures.
11. If a leak was not found in Step 10 and the vehicle is equipped with On Board Refueling Vapor Recovery, connect the EVAP pressure/purge Diagnostic station with the fuel cap adapter (J 41415-40) to the fuel tank filler neck and repeat Step 10. These ORVR vehicles are equipped with a check valve at the base of the filler tube which may not allow pressure from the EVAP service port to be applied to the filler tube and the fuel cap.
With pressure applied it may be necessary to disconnect the EVAP lines at the components to verify that a line or component is not restricted. A restriction would prevent a vacuum (or the Step 10 test pressure) from forming in the fuel tank.
16. An EVAP Pressure sensor that does not correctly respond to vacuum (or pressure) will cause this DTC to set.
The EVAP Pressure Sensor monitors a range from 7.5 in. H2O of pressure to -17.5 in. H2O of pressure (vacuum).