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 vapor lines |
| • | The fuel cap |
| • | The evaporative emission canister |
| • | The purge lines |
| • | The EVAP purge solenoid |
The evaporative leak detection diagnostic strategy is based on applying a vacuum to the EVAP system and monitoring the vacuum decay rate. The VCM monitors the vacuum level via the fuel tank pressure sensor input. At an appropriate time, the EVAP purge solenoid and the EVAP vent solenoid turn ON, allowing the 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 malfunctioning EVAP purge solenoid is indicated. The following conditions can cause this problem:
| • | A disconnected or malfunctioning fuel tank pressure sensor |
| • | A missing, malfunctioning, improperly installed, or loose fuel cap |
| • | A disconnected, damaged, pinched, or blocked EVAP purge line |
| • | A disconnected or damaged EVAP vent hose |
| • | A disconnected, damaged, pinched, or blocked fuel tank vapor line |
| • | A disconnected or malfunctioning EVAP purge solenoid |
| • | A disconnected or malfunctioning EVAP vent solenoid |
| • | An open ignition feed circuit to the EVAP vent or purge solenoid |
| • | A damaged EVAP canister |
| • | A leaking fuel sender assembly O-ring |
| • | A leaking fuel tank or fuel filler neck |
Any of the above conditions can set a DTC P0440.
Diagnostic Aids
Important: An accurate indication of fuel level is required for the VCM to pass or fail the EVAP system. Always diagnose fuel level sensor DTC's before performing this diagnostic. Always check for fuel level sensor DTC's stored in history.
Check for the following conditions:
| • | A loose, missing, damaged, incorrect or improperly installed fuel cap |
| • | Missing or damaged O-rings at EVAP canister fuel vapor and purge line fittings |
| • | A cracked or punctured EVAP canister |
| • | A damaged or disconnected EVAP purge line, vent hose or fuel tank vapor line |
| • | Incorrectly routed or damaged EVAP system purge and vapor lines |
| • | A poor connection at the VCM: Inspect the harness connectors for the following conditions: |
| - | Backed out terminals |
| - | Improper mating |
| - | Broken locks |
| - | Improperly formed or damaged terminals |
| - | poor terminal to wire connection |
| • | A damaged harness: Inspect the wiring harness to the EVAP vent solenoid, EVAP purge solenoid and the fuel tank pressure sensor for an intermittent, open or short circuit |
| • | A kinked, pinched or plugged EVAP purge or fuel tank vapor line. Verify that the lines are not restricted |
Refer to Evaporative Emission System Cleaning before starting repairs.
Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
-
Inspect the service port. Make sure that the dust cap and 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 solenoid valve.
Connect a hand vacuum pump to the service port by placing the hose/adaptor over the unthreaded end portion of the service port.
Apply vacuum to 5 in. Hg. If the vacuum does not hold replace the service port (may require line replacement).
-
If the vehicle passes the Service Bay Test then an intermittent leak or restriction had occurred. Check the fuel tank cap for a possible loose or off condition 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.
-
Refer to the information supplied with the EVAP pressure/purge diagnostic cart on proper setup and adjustment procedures.
-
If a leak was not found in Step 9 and the vehicle is equipped with On Board Refueling Vapor Recovery connect the EVAP pressure/purge Diagnostic station with the fuel cap adaptor (J 41415-40) to the fuel tank filler neck and repeat Step 9. 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 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.
The EVAP Pressure Sensor monitors a range from 7.5 in. H2O of pressure to -17.5 in. H2O of pressure (vacuum).
Step | Action | Value(s) | Yes | No | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 |
Important: Before clearing the DTCs, use the scan tool to record the Freeze Frame and the Failure Records for reference. This data will be lost when the Clear Info function is used. Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||||||||||
2 | Check for DTCs P0440, P0442, P0446, P0452, P0453, P0461, P0462, P0463 and P1441. Are any of the above EVAP system DTC's stored in HISTORY? | -- | Go to DTCs that are set. | |||||||||
Inspect the EVAP system for the following conditions:
Repair the EVAP system if needed. Was a repair made to the EVAP system? | -- | |||||||||||
|
Important: Before proceeding with the Service Bay Test the vehicle must meet the
following operating criteria:
If any of the above conditions are not met the scan tool will display Test Aborted upon activating the Service Bay Test.
Does the vehicle pass the Service Bay Test? | -- | Condition not present. Go to Test Descriptions and Diagnostic Aids | ||||||||||
5 |
Is the vacuum at or above the specified value? | 12 in. Hg. | ||||||||||
6 |
Can the specified value be obtained and held? | 5 in. Hg. | ||||||||||
7 |
Can the specified value be obtained and held? | 5 in. Hg. | ||||||||||
8 |
Was a problem found and repaired? | -- | ||||||||||
|
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 in. H2O of pressure to the EVAP system. Was a leak found and repaired? | -- | |||||||||||
Was a problem found and repaired? | -- | |||||||||||
11 |
Is the test light ON? | -- | ||||||||||
12 |
Is the test light ON? | -- | ||||||||||
13 |
Is the repair complete? | -- | -- | |||||||||
14 |
Was a problem found and repaired? | -- | ||||||||||
15 |
Is the test light ON? | -- | ||||||||||
16 |
Is the test light ON? | -- | ||||||||||
17 |
Is the repair complete? | -- | -- | |||||||||
18 |
Was problem found and repaired? | -- | ||||||||||
19 |
Important: Inspect the EVAP Purge Solenoid Valve and the purge line for carbon contamination. Refer to Diagnostic Aids . Replace the EVAP Purge Solenoid Valve. Is the replacement complete? | -- | -- | |||||||||
20 | Replace the EVAP Vent Valve. Is the replacement complete? | -- | -- | |||||||||
21 | Replace the EVAP Vapor Canister. Is the replacement complete? | -- | -- | |||||||||
Do the values indicate the same amount of vacuum in the EVAP system to within the range specified? | 2 in. H2O | Go to Step 3 | ||||||||||
23 | Replace the Fuel Tank Pressure Sensor. Refer to Fuel Tank Pressure Sensor Replacement . Is the replacement complete? | -- | -- | |||||||||
24 |
Is the action complete? | -- | -- | |||||||||
25 |
Is the action complete? | -- | -- | |||||||||
26 | Operate the vehicle under the conditions necessary in order to run the DTC. Does the scan tool display any DTCs in the Freeze Frame and Failure Records? | -- | Go to applicable DTC table | System OK |
