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 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 the engine vacuum to draw a small vacuum on the entire evaporative emission system. After the desired vacuum level has been achieved, the EVAP purge solenoid turns OFF, sealing the system. A leak is detected by monitoring for a decrease in the vacuum level over a given time period. A small leak in the system will cause DTC P0442 to be set.
Conditions for Running the DTC
| • | No MAP sensor DTCs are active. |
| • | No TP sensor DTCs are active. |
| • | No VS sensor DTCs are active. |
| • | No O2 sensor DTCs are active. |
| • | No ECT sensor DTCs are active. |
| • | No IAT sensor DTCs are active. |
| • | DTC P0125 is not active. |
| • | The fuel level is between 12.5-87 percent. |
| • | The ECT is between 4°C and 30°C (39°F to 86°F). |
| • | The IAT is between 4°C and 30°C (39°F to 86°F) |
| • | The cold start temperature difference, or the ECT minus the IAT, is less than: |
| 1.5°C when the IAT is more than the ECT |
| 8°C when the ECT is more than the IAT |
| • | The BARO is more than 72 kPa. |
| • | The change in fuel tank vacuum is less than 0.6 inch of H2O, or the change in fuel level is less than 8 percent. |
| • | The throttle position is less than 75 percent. |
| • | The vehicle speed is less than 65 MPH. |
| • | The fuel tank vacuum level remains above a calibrated value for a specified number of seconds. |
Conditions for Setting the DTC
The EVAP system is unable to hold a specified vacuum level for a calibrated number of seconds.
Action Taken When the DTC Sets
| • | This is a type A DTC that behaves like a B type, in which the VCM illuminates the MIL after the second key cycle. |
| • | The VCM stores the conditions that were present when the DTC sets as the Freeze Frame and Failure Records data. |
Conditions for Clearing the MIL or DTC
| • | The control module turns OFF the MIL after 3 consecutive drive trips when the test has run and passed. |
| • | A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles. A warm-up cycle occurs when the coolant temperature has risen 22°C (40°F) from the startup coolant temperature and the engine coolant reaches a temperature that is more than 70°C (158°F) during the same ignition cycle. |
| • | Use a scan tool in order to clear the DTCs. |
Diagnostic Aids
Important: An accurate indication of the fuel level is required for the VCM to properly pass or fail this DTC. Always diagnose the fuel level sensor DTCs before performing this DTCs diagnostic table. Always check for fuel level sensor DTCs stored in History.
Check for the following:
| • | A loose, missing, damaged, incorrect, or improperly installed fuel cap |
| • | Missing or damaged O-rings at the 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 faulty connection at the VCM-Inspect the harness connectors for: |
| - | Backed-out terminals |
| - | Improper mating |
| - | Broken locks |
| - | Improperly-formed or damaged terminals |
| - | Faulty terminal-to-wire connections |
| • | A damaged harness-Inspect the wiring harness to the EVAP vent solenoid, the EVAP purge solenoid, and the fuel tank pressure sensor for an intermittent, an open, or a 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.
Reviewing the Failure l 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.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
Inspect the service port. Make sure that the valve core is not damaged. If you 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 and adaptor over the unthreaded end portion of the service port.
Apply vacuum to 5 inches Hg. If the vacuum does not hold, replace the entire purge line which contains the service port.
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If the vehicle passes the Service Bay Test then an intermittent leak has occurred. Check the fuel tank cap for a possible loose or leaking 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 and purge diagnostic cart for proper setup and adjustment procedures.
-
An EVAP pressure sensor that does not correctly respond to pressure or vacuum will cause this DTC to set.
The EVAP pressure sensor monitors a range from 7.5 inches Hg of pressure to -17.5 inches Hg of vacuum.
Step | Action | Values | Yes | No | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||||||||||
2 | Check for DTCs P0440, P0446, P0452, P0453, P0461, P0462, P0463, and P1441. Are any other EVAP system DTCs stored in HISTORY? | -- | Go to applicable DTC | |||||||||
Did you make a repair to the EVAP system? | -- | |||||||||||
|
Important: Before proceeding with the Service Bay Test the vehicle must meet the
following operating criteria:
If any of these 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? | -- | Go to Test Description | ||||||||||
5 |
Can you obtain and hold the specified value of vacuum? | 12 in Hg | ||||||||||
6 |
Can you obtain and hold the specified value of vacuum? | 5 in Hg | ||||||||||
7 |
Can you obtain and hold the specified value of vacuum? | 5 in Hg | ||||||||||
8 |
Did you replace the EVAP vent line? | -- | ||||||||||
|
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 Hg) gauges on the EVAP pressure/purge diagnostic station before proceeding with diagnosis.
Important: Do Not apply more than 15 in Hg of pressure to the EVAP system. Did you find and repair a leak? | -- | |||||||||||
10 |
Important: Inspect the EVAP purge solenoid valve and the purge line for carbon contamination. Refer to diagnostic aids. Replace the EVAP purge solenoid valve. Refer to Evaporative Emission Canister Purge Solenoid Valve Replacement . Is the replacement complete? | -- | -- | |||||||||
11 | Replace the EVAP vent valve. Refer to Evaporative Emission Vent Valve Replacement . Is the replacement complete? | -- | -- | |||||||||
12 | Replace the EVAP vapor canister. Refer to Evaporative Emission Canister Replacement . Is the replacement complete? | -- | -- | |||||||||
Do both values indicate the same amount of vacuum in the EVAP system to within the range specified? | + or - 2 in Hg | |||||||||||
14 | Replace the EVAP fuel tank pressure sensor. Refer to Fuel Tank Pressure Sensor Replacement . Is the replacement complete? | -- | -- | |||||||||
15 |
Does the scan tool indicate the diagnostic Passed? | -- | -- | |||||||||
16 | Does the scan tool display any additional undiagnosed DTCs? | -- | Go to applicable DTC | System OK |
