Circuit Description
Applying a vacuum to the EVAP system and monitoring for a vacuum decay checks the evaporative emission system. The Control Module monitors the vacuum level through the fuel tank vacuum sensor signal. At an appropriate time, the EVAP canister purge valve and the EVAP vent solenoid turn ON, allowing the engine to draw a small vacuum on the entire evaporative emission system. After the desired vacuum level has been achieved, the EVAP canister purge valve turns OFF, sealing the system. A leak is detected by monitoring for a decrease in the vacuum level over a given time period, when all other variables remain constant. A leak, a blockage or a malfunctioning component in the system causes a DTC to set.
Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
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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 the service port is suspect of leakage 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).
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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.
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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.
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 Capture Info to save the Freeze Frame and Failure Records for reference. The control module's data is deleted once the Clear Info function is used. Did you perform the Powertrain On-board Diagnostic (OBD) System check? | -- | ||||||||||
2 | Check for DTC's P0442, P0446, P0452, P0453, P0461, P0462, P0463 and P1441. Are any of the above EVAP system DTC's stored in HISTORY? | -- | Go to the 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 |
Does the Scan Tool indicate the diagnostic Passed? | -- | -- | |||||||||
26 | Does the Scan Tool display any additional undiagnosed DTCs? | -- | Go to applicable DTC table | System OK |
