The EVAP small leak test applies vacuum to the evaporative emission (EVAP) system and monitors vacuum decay. The control module monitors the fuel tank pressure (FTP) sensor signal to determine the vacuum decay rate. At an appropriate time, the control module turns the EVAP canister purge valve ON (open) and the EVAP vent valve ON (closed). This allows the engine to draw a vacuum on the EVAP system. At a calibrated time, or vacuum level, the control module turns the purge valve OFF (closed), sealing the system, and monitors the FTP sensor input in order to determine EVAP system vacuum decay. If the system detects a leak larger than a calibrated amount DTC P0442 will set.
• | DTCs P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0122, P0123, P0452, or P0453 are not set. |
• | The ignition voltage is between 10-18 volts. |
• | The barometric pressure (BARO) is more than 75 kPa. |
• | The fuel level is between 15-85 percent. |
• | The engine coolant temperature (ECT) is between 4-30°C (39-86°F). |
• | The intake air temperature (IAT) is between 4-30°C (39-86°F). |
• | The start up ECT and IAT are within 9°C (16°F) of each other. |
• | The vehicle speed sensor (VSS) is less than 121 km/h (75 mph). |
The EVAP system can achieve vacuum but a vacuum decay is detected during the diagnostic test.
• | The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails. |
• | The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records. |
• | The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
• | A current DTC, Last Test Failed, clears when the diagnostic runs and passes. |
• | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
• | Clear the MIL and the DTC with a scan tool. |
To aid in locating intermittent leaks, use the J 41413 EVAP Pressure and Purge Station to pressurize the EVAP system. Move all EVAP components while testing with the J 41416 Ultrasonic Leak Detector.
The numbers below refer to the step numbers on the diagnostic table.
This step verifies that a failure condition is active.
This step verifies that repairs are complete.
This step verifies that no other condition is present.
Step | Action | Values | Yes | No | ||||||||||||||||||||
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Schematic Reference: Evaporative Emissions Hose Routing Diagram | ||||||||||||||||||||||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |||||||||||||||||||||
2 | Does the scan tool indicate that DTC P0446, P0452, P0453, P0461, P0462, P0463, or P1441 also set? | -- | Go to Step 3 | |||||||||||||||||||||
3 |
Did you find and correct the condition? | -- | Go to Step 6 | Go to Step 4 | ||||||||||||||||||||
Important: Always zero the EVAP pressure and vacuum (in H2O) gages on the EVAP pressure/purge diagnostic station before proceeding with diagnosis.
Does the EVAP system pressure remain constant? | 15 in H2O | Go to Diagnostic Aids | Go to Step 5 | |||||||||||||||||||||
5 |
Important: It may be necessary to partially lower the fuel tank to inspect components located in the upper portion of the tank.
Did you find and repair the condition? | 15 in H2O | Go to Step 6 | Go to Diagnostic Aids | ||||||||||||||||||||
Does the EVAP system pressure remain constant? | 15 in H2O | Go to Step 7 | Go to Step 2 | |||||||||||||||||||||
With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to Fuel Tank Replacement | System OK |