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. 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 with all other variables remaining constant. A small leak in the system will cause DTC P0442 to be set.
Conditions for Running the DTC
- No active MAP sensor DTCs
- No active TP sensor DTCs
- No active VS sensor DTCs
- No active HO2S DTCs
- No active ECT sensor DTCs
- No active IAT sensor DTCs
- DTC P0125 not active
- The fuel level is greater that 12.5 percent but less than 87.5 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 (ECT minus IAT) is less than - 1.5°C when the IAT is greater than the ECT
- The cold start temperature difference (ECT minus IAT) is less than - 8°C when the ECT is greater than the IAT
- The BARO is greater than 72.5 kPa
- The change in fuel tank vacuum is less than 0.6 in. 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 EVAP system vacuum reaches a calibrated value for a specified number of seconds
Conditions for Setting the DTC
The VCM detects a drop in the EVAP system vacuum level within 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 during the second key cycle. |
| • | The VCM stores the conditions that were present when the DTC sets as a Freeze Frame and Fail 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
Check for the following conditions:
| • | Damaged O-rings at the EVAP canister fuel vapor and purge line fittings |
| • | A cracked or punctured EVAP canister |
| • | A damaged source vacuum line, an EVAP purge line, a vent hose or fuel tank vapor line |
| • | 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 |
| - | A 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 missing or damaged weather-pack on the EVAP Purge Solenoid connector. |
Refer to EVAP System Cleaning before starting the repairs.
Reviewing the Fail Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to set occurs. This may assist in diagnosing the condition.
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 are 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).
-
If the vehicle passes the Service Bay Test then an intermittent leak had 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/purge diagnostic cart on 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 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 DTCs P0440, P0446, P0452, P0453, P0461, P0462, P0463, and P1441. Are any other 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? | -- | Fault not present. Go to Test Descriptions | ||||||||||
5 |
Can the specified value of vacuum be obtained and held? | 12 in. Hg. | ||||||||||
6 |
Can the specified value of vacuum be obtained and held? | 5 in. Hg. | ||||||||||
7 |
Can the specified value of vacuum be obtained and held? | 5 in. Hg. | ||||||||||
8 |
Was the EVAP Vent line replaced? | -- | ||||||||||
|
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? | -- | |||||||||||
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. Is the replacement complete? | -- | -- | |||||||||
11 | Replace the EVAP Vent Valve. Is the replacement complete? | -- | -- | |||||||||
12 | Replace the EVAP Vapor Canister. 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. H2O | |||||||||||
14 | Replace the EVAP Fuel Tank Pressure Sensor. 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 table | System OK |
