System Description
The EVAP Small Leak Test is based on applying vacuum to the evaporative emissions (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 are turned on allowing engine vacuum to draw a vacuum on the entire evaporative emission system. After the desired vacuum level has been achieved, the EVAP purge valve is turned off, sealing the system. A leak is detected by monitoring for a decrease in vacuum level over a given time period, all other variables remaining constant. A small leak in the system will cause DTC P0442 to be set.
The EVAP System includes the following components:
| • | The fuel tank |
| • | The EVAP vent valve |
| • | The EVAP canister purge valve |
| • | The EVAP canister |
| • | The fuel pipes and hoses |
| • | The EVAP vapor and purge pipes |
| • | The EVAP fresh air vent hose |
| • | The fuel fill cap |
Conditions for Running the DTC
| • | TP, IAT, FTP, ECT or MAP sensor DTCs are not set. |
| • | System voltage is between 10-18 volts. |
| • | The DTC P0440 diagnostic test has Passed. |
| • | Startup ECT is not more than 4-30°C (39-86°F). |
| • | Startup ECT is not more than 8°C (14°F) more than IAT startup temperature. |
| • | Startup IAT not more than 4-30°C (39-86°F). |
| • | Fuel tank level is between 15-85 percent. |
| • | BARO is more than 75kPa. |
| • | IAT is less than 30°C (86°F). |
| • | TPS between 7-35 percent. |
| • | VSS below 129 km/h (80 mph). |
Conditions for Setting the DTC
A vacuum decay condition indicating a small leak is detected during the diagnostic test.
Action Taken When the DTC Sets
| • | The PCM will illuminate the malfunction indicator lamp (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 will turn the MIL OFF during the first trip in which the diagnostic has been run and Passed. |
| • | The history DTC will clear when the PCM turns off the MIL. |
| • | The DTC can be cleared by using a scan tool. |
Diagnostic Aids
The following conditions will set DTC P0442:
| • | Loose or malfunctioning fuel fill cap |
| • | Damaged EVAP purge or vapor pipes |
| • | Damaged EVAP fresh air vent hose |
| • | Malfunctioning EVAP vent valve |
| • | Damaged EVAP canister |
| • | Leaking fuel tank, fuel sender assembly O-ring or pressure relief valve |
| • | Leaking fuel filler neck or seal |
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.
If the condition is intermittent refer to Intermittent Conditions .
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This test verifies that the EVAP purge valve can be commanded ON and OFF.
-
This test verifies that the EVAP vent valve can be commanded ON and OFF.
-
Refer to the information supplied with the EVAP pressure/purge diagnostic cart on proper setup and adjustment procedures.
-
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 9 test pressure) from forming in the fuel tank.
-
An EVAP pressure sensor that does not correctly respond to vacuum (or pressure) will cause this DTC to set.
Step | Action | Values | Yes | No | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Powertrain On-board Diagnostic (OBD) System check? | -- | ||||||||||
2 | Are DTCs P0446, P0452, P0453, P0461, P0462, P0463, P1441 set? | -- | Go to applicable DTC | |||||||||
3 | Inspect the EVAP system for the following conditions:
Repair the EVAP system if needed. Did you find and correct the condition? | -- | ||||||||||
Command the EVAP
purge valve ON and OFF with the scan tool. Refer to
Do you hear an audible click as the EVAP purge valve is commanded ON and OFF? | -- | |||||||||||
Command the EVAP purge vent
valve ON and OFF with the scan tool. Refer to
Do you hear an audible click as the EVAP vent valve is commanded ON and OFF? | -- | |||||||||||
6 |
Is the vacuum at or above the specified value? | 12 in Hg | ||||||||||
7 |
Can the specified value be obtained and held? | 5 in Hg | ||||||||||
8 |
Can the specified value be obtained and held? | 5 in Hg | ||||||||||
9 |
Did you find and correct the condition? | -- | ||||||||||
|
Important: The following steps require the EVAP pressure/purge diagnostic station J 41413 and the ultrasonic leak detector J 41416 . Always zero the EVAP pressure and vacuum (in. H2O) gauges on the EVAP pressure/purge diagnostic station before proceeding with diagnosis.
Important: Do Not apply more than 15 inches H2O of pressure to the EVAP system. Did you find and correct the condition? | -- | |||||||||||
Inspect the EVAP system for restrictions. Refer to test description. Did you find and correct the condition? | -- | |||||||||||
12 |
Does the test lamp illuminate? | -- | ||||||||||
13 |
Does the test lamp illuminate when the EVAP purge valve is commanded ON? | -- | ||||||||||
14 | Test the EVAP purge valve control circuit for an open or short to B+. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | ||||||||||
15 |
Is the test lamp illuminated? | -- | ||||||||||
16 |
Does the test lamp illuminate when the EVAP vent valve is commanded ON? | -- | ||||||||||
17 | Test the EVAP vent valve control circuit for an open or short to B+. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | ||||||||||
18 | Repair the EVAP purge valve ignition voltage circuit for an open or short to ground. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | -- | |||||||||
19 | Repair the EVAP vent valve ignition voltage circuit for an open or short to ground. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | -- | |||||||||
20 | Inspect the vacuum source to the EVAP purge valve for damage or a disconnect. Did you find and correct the condition? | -- | ||||||||||
21 |
Important: :
Replace the EVAP purge valve. Refer to Evaporative Emission Canister Purge Solenoid Valve Replacement . Is the replacement complete? | -- | -- | |||||||||
22 |
Important: Inspect for poor connections at the harness connector of the EVAP vent valve. Replace the EVAP vent valve. Refer to Evaporative Emission Vent Valve Replacement . Is the replacement complete? | -- | -- | |||||||||
23 | Replace the EVAP vapor canister. Refer to Evaporative Emission Canister Replacement . Is the replacement complete? | -- | -- | |||||||||
Does the EVAP pressure/purge diagnostic station vacuum gauge reading correspond to the fuel tank pressure sensor value displayed on the scan tool ? | -- | Go to | ||||||||||
25 | Replace the fuel tank pressure sensor. Refer to Fuel Tank Pressure Sensor Replacement . Did you complete the replacement? | -- | -- | |||||||||
26 |
Important: Inspect for poor connections at the harness connector of the PCM. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Did you complete the replacement? | -- | -- | |||||||||
27 |
Does the EVAP system pressure stay constant? | 10 in Hg | ||||||||||
28 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to applicable DTC | System OK |
