Circuit Description
The evaporative system includes the following components:
| • | The fuel tank. |
| • | The EVAP vent solenoid. |
| • | The fuel tank pressure sensor. |
| • | The fuel pipes and hoses. |
| • | The fuel cap. |
| • | The EVAP vapor lines. |
| • | The EVAP purge lines. |
| • | The evaporative emission canister. |
| • | The EVAP purge solenoid. |
The evaporative leak detection diagnostic strategy 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 purge solenoid and the EVAP vent 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 purge solenoid is indicated. This can be caused by the following conditions:
| • | Disconnected or faulty fuel tank pressure sensor. |
| • | Missing or faulty fuel 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 purge solenoid. |
| • | Disconnected or faulty EVAP vent solenoid. |
| • | Open ignition feed circuit to the EVAP vent or purge solenoid. |
| • | Damaged evaporative emissions 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 Setting the DTC
| • | No TP sensor, ODM, IAT sensor, or MAP sensor DTCs set. |
| • | Start-up engine coolant temperature is between 4°C and 30°C (40°F and 86°F). |
| • | Start-up engine coolant temperature is not more than 8°C (14°F) greater than start-up intake air temperature. |
| • | Start-up Intake air temperature is between 4°C and 30°C (40°F and 86°F). |
| • | Start-up intake air temperature not more than 2°C (4°F) greater than start-up engine coolant temperature. |
| • | Fuel tank level is between 15% and 85%. |
| • | BARO is greater than 75kPa. |
| • | The vehicle has been driven at least 11 miles. |
| • | The EVAP system is unable to achieve or maintain vacuum during the diagnostic test. |
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 a system has passed, or if the battery has been disconnected, the diagnostic must fail during 2 consecuitive 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 Fail Records data. |
Conditions for Clearing the MIL/DTC
| • | The PCM will turn the MIL OFF when the diagnostic has been run and the fault condition is no longer present. |
| • | A history DTC P0440 will clear after 40 consecutive warm-up cycles have occurred without a fault. |
| • | This DTC can be cleared by using the scan tool Clear Info function or by disconnecting the PCM battery feed. |
Diagnostic Aids
Check for the following conditions:
| • | 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 solenoid, the EVAP purge solenoid, 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. |
| • | Faulty or damaged canister. |
| A faulty canister may intermittently allow charcoal into the EVAP purge solenoid, vacuum switch, and associated lines causing a DTC to be set. Use the following procedure to check for a carbon release condition: |
| 1. | Turn off the ignition switch. |
| 2. | Remove the EVAP purge solenoid. Refer to EVAP Canister Purge Solenoid. |
| 3. | Lightly tap the purge solenoid and (if applicable) the vacuum switch 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
|
| 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 solenoid 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 purge solenoid. Refer to Evaporative Emission Canister Purge Solenoid . |
| • | The EVAP canister. Refer to Evaporative Emission Canister Replacement 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.
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:
| • | 1 in H2O = 0.07 in Hg = 0.0361 psi. |
| • | 5 in H2O = 0.36 in Hg = 0.180 psi. |
| • | 10 in H2O = 0.73 in Hg = 0.361 psi. |
| • | 15 in H2O = 1.10 in Hg = 0.541 psi. |
| • | 20 in H2O = 1.46 in Hg = 0.722 psi. |
Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
-
If a vent solenoid or EVAP purge solenoid electrical fault is present, the purge system will not operate correctly. Repairing the electrical fault will very likely correct the condition that set DTC P0440.
-
Checks the fuel tank pressure sensor at ambient pressure.
-
Determines whether or not the EVAP system can be sealed sufficiently to be pressurized. If not, the large leak must be located and corrected before continuing with diagnosis.
-
Verifies that the fuel tank pressure sensor accurately reacts to EVAP system pressure changes.
-
Checks for a blocked EVAP purge solenoid. The PCM commands the EVAP purge solenoid off (open) and the vent solenoid on (closed) with the scan tool System Perf. EVAP output control function activated. Any pressure in the system should be released through the EVAP purge solenoid within a few seconds when System Perf. is activated.
-
Ensures that sufficient source vacuum is present at the EVAP purge solenoid.
Step | Action | Value(s) | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
1 | Was the Powertrain On Board Diagnostic (OBD) System Check performed? | -- | ||||||||
Is DTC P1655 EVAP Purge Solenoid Control Circuit or DTC P1675 EVAP Vent Solenoid Control Circuit also set? | -- | Go to the other DTC first Refer to Powertrain Control Module Diagnosis | ||||||||
Is Fuel Tank Pressure at the specified value? | 0 in. H2O | |||||||||
|
Important: : Before continuing with diagnosis, zero the EVAP Pressure and Vacuum
(inches of H2O) gauges on the
Can specified value be achieved? | 5 in. H2O | |||||||||
Is Fuel Tank Pressure at the specified value? | 5 in. H2O | |||||||||
6 |
Can vacuum be maintained at the specified value? | 5 in. Hg | ||||||||
7 |
Was a problem found? | -- | ||||||||
Does the EVAP pressure decrease to the second specified value within 15 seconds while System Performance is Activated? | 5 in. H2O 0 in. H2O | |||||||||
Is the source vacuum level greater than the specified value? | -15 in. Hg | Refer to Diagnostic Aids | ||||||||
10 |
Was a problem found? | -- | ||||||||
11 |
Was a problem found? | -- | ||||||||
12 |
Is the action complete? | -- | -- | |||||||
13 | Replace the EVAP purge solenoid. Refer to Evaporative Emission Canister Purge Solenoid . Is the action complete? | -- | -- | |||||||
14 |
Important : Check for carbon release into the EVAP System. Refer to Diagnostic Aids. Is the action complete? | -- | -- | |||||||
15 | Replace the EVAP vent solenoid. Refer to Evaporative Emission Vent Valve Replacement . Is the action complete? | -- | -- | |||||||
16 |
Does the EVAP pressure decrease to less than the second specified value within 2 minutes? | 15 in. H2O 10 in. H2O | System OK |
