GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2000 🢒 Corvette 🢒 DTC 🢒 DTC P0442 Evaporative Emission (EVAP) System Small Leak Detected
Table 1: DTC P0440 and P0442

Object Number: 604997 Size: MF
Engine Controls Component Views
Evaporative Emissions Vent Valve Solenoid
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

Circuit Description

The PCM tests the EVAP system for the following conditions:

    • Large and small leaks
    • Excess vacuum
    • Purge flow during non-commanded conditions
    • Fuel Level and Fuel Pressure sensor faults
    • EVAP Purge and Vent Valve faults

The PCM monitors the fuel tank pressure sensor in order to determine the level of vacuum/pressure in the EVAP system. The PCM commands both the EVAP Purge Solenoid and the EVAP Vent Valve ON when the Conditions for Running the DTC are met in order to apply an engine vacuum to the EVAP system. The PCM commands the EVAP Purge Solenoid OFF once the system has reached a predetermined level of vacuum. The EVAP system should HOLD the vacuum in the sealed system. The PCM sets this DTC in order to indicate a small leak if the EVAP system fails to hold a predetermined level of vacuum for a predetermined length of time. This DTC sets after failing the above test twice.

Conditions for Running the DTC

    •  DTCs P0107, P0108, P0112, P0113, P0117, P0118, P0125, P0420, P0430, P0500, P0502, P0503, P0562, P0563, P1120, P1220, P1221, and HO2S DTCs are not set.
    • The barometric (BARO) pressure is greater than 72.5 kPa (10.5 psi)
    • The fuel level is between 12.5 percent and 87.5 percent of full capacity.
    • The engine coolant temperature (ECT) is between 4°C (39°F) and 30°C (86°F).
    • The intake air temperature (IAT) is between 4°C (39°F) and 30°C (86°F).
    • The start up ECT and IAT are within 9°C (16°F) of each other.
    • The throttle position (TP) angle is less than 75 percent during the weak vacuum test.
    • The vehicle speed is less than 113 km/h (70 mph) during the weak vacuum test.

Conditions for Setting the DTC

The vacuum in the EVAP system decays (leaks) at too fast a rate.

Important: This DTC does NOT report a first failed test. A first fail of this DTC will have a scan tool status as Not Run. Use the scan tool data display parameter of EVAP Test Result to determine if this DTC has failed or passed for this ignition cycle.

Action Taken When the DTC Sets
    • The PCM illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
    • The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the PCM stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the PCM records the operating conditions at the time of the failure. The PCM writes the conditions to the Freeze Frame and updates the Failure Records.

Conditions for Clearing the MIL/DTC
    • The PCM turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
    • A last test failed, or current DTC, clears when the diagnostic runs and does not fail.
    • A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
    • Use a scan tool in order to clear the MIL and the DTC.

Diagnostic Aids

Important: 

   • Remove any debris from the PCM/TAC module connector surfaces before servicing the PCM/TAC module. Inspect the PCM/TAC module connector gaskets when diagnosing/replacing the modules. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion into the PCM/TAC modules.
   • For any test that requires probing the PCM or a component harness connector, use the Connector Test Adapter Kit J 35616 . Using this kit prevents damage to the harness/component terminals. Refer to Using Connector Test Adapters in Wiring Systems.

    • An accurate indication of fuel level is required for the PCM to properly Pass or Fail this DTC. Always diagnose fuel level sensor DTC's before performing this diagnostic table. Always monitor for fuel level sensor DTCs stored as History.
    • The Service Bay Test may have to be performed in cold ambient air temperatures when the vehicle is running a winter grade fuel. The scan tool displays a message when the service bay test does not run.
    • Perform a physical inspection of the EVAP system. Inspect for the following conditions:
       - A loose, missing, defective, or incorrect fuel tank cap
       - Incorrectly routed or defective EVAP system vacuum and vapor lines
       - A malfunctioning or damaged vapor canister
    • Inspect for charcoal release from the vapor canister. Refer to the Evaporative Emission System Cleaning procedure.
    • The vacuum and pressure in the EVAP system is measured in inches of H2O (water). Most gauges measure vacuum in inches of Hg (mercury) and pressure in psi (pounds per square inch). The following table illustrates how the values compare:

in. H2O

in. Hg.

psi

1 in. H2O

0.07 in. Hg

0.0361 psi.

5 in. H2O

0.36 in. Hg

0.180 psi.

10 in. H2O

0.73 in. Hg

0.361 psi.

15 in. H2O

1.10 in. Hg

0.541 psi.

Conditions for Running the Service Bay Test

    • The battery voltage is between 10.5 and 18.0 volts.
    • The fuel level is between 15 percent and 85 percent of the full capacity.
    • The engine temperature is between 3.5°C (38°F) and 35°C (95°F).
    • A fuel tank pressure sensor that is stuck in range will not cause DTC P0452/P0453 to set, but will cause DTC P0440/P0442 to set.
    • An open fuel tank pressure sensor ground circuit could cause this DTC to set.
    • For an intermittent, refer to Symptoms .

Test Description

The numbers below refer to the step numbers on the Diagnostic Table.

  1. The components in this system are difficult to access . Thoroughly inspect all areas of the EVAP system. A fuel tank cap that is loose or off can cause this DTC to set.

    2.

  2. The Service Bay Test will not run if the fuel level sensor voltage is out of range. The fuel level sensor voltage should be between 0.7-2.5 volts for both sensors. An intermittent leak or restriction is indicated if the vehicle passes the Service Bay Test.

    If the Service Bay Test can not be run, proceed to Step 5.

    3.

  3. This step is testing for a Fuel Tank Pressure sensor that is stuck in range. A sensor that is stuck in range will not cause DTC P0452/P0453 to set, but will cause DTC P0440/P0442 to set.

    4.

  4. A Fuel Tank Pressure sensor that does not correctly respond to pressure (or vacuum) causes this DTC to set.

    The Fuel Tank Pressure sensor range is from 7.5 in. H2O of pressure to -17.5 in. H2O of pressure (vacuum).

    In order to test the Fuel Tank Pressure sensor for vacuum response, command the EVAP Purge Solenoid Valve ON with the engine running and quickly SEAL the system. Leaving the EVAP Purge Solenoid Valve ON for a longer period of time allows a greater level of vacuum to develop.

    5.

  5. This step verifies if the Fuel Tank Pressure sensor responds when a vacuum is applied to the sensor.

    6.

  6. This step tests the EVAP Purge Solenoid Valve for a leak.

    7.

  7. Remove necessary components to access EVAP components. Refer to the information supplied with the EVAP pressure/purge diagnostic cart on proper setup and adjustment procedures.

    8.

  8. This step is testing for a leak in the EVAP chassis pipe that comes from the EVAP Purge Solenoid Valve.

    9.

  9. This step is testing the EVAP Canister and EVAP vent valve for a leak.

    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 10 test pressure) from forming in the fuel tank.

    10.

  10. This step is testing the complete fuel tank assembly for a leak. Thoroughly inspect the top of the fuel tanks for a leak.

    11.

  11. 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 pressure from forming in the fuel tank.

DTC P0440 and P0442

Step

Action

Values

Yes

No

1

Did you perform the Powertrain On-Board Diagnostic (OBD) System Check?

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

2

Are any other EVAP system DTC's set?

--

Go to Applicable DTC

Go to Step 3

3

  1. Inspect the EVAP system for the following conditions:
    2. • A loose, incorrect, defective or missing fuel tank cap.
    • Disconnected, improperly routed, kinked or damaged EVAP system purge lines.
    • A damaged EVAP system component.
    • A damaged Fuel Pressure Connection Valve or a loose, missing, or damaged dust cap. Refer to the test description for additional information.
  2. Repair the EVAP system as necessary.

Did you find and repair the condition?

--

Go to Step 24

Go to Step 4

4

Important: Ensure that The Conditions for Running the Service Bay test are met before proceeding with this diagnostic. Refer to Diagnostic Aids.

Perform the EVAP system Service Bay Test using a scan tool.

Does the EVAP diagnostic pass the Service Bay Test?

--

Go to Diagnostic Aids

Go to Step 5

5

  1. Turn ON the ignition leaving the engine OFF.
  2. Remove the fuel tank cap.
  3. Monitor the fuel tank pressure using a scan tool.

Is the Fuel Tank Pressure near the specified value?

0 in. Hg.

Go to Step 6

Go to Step 7

6

Important: The DTCs must be cleared from the PCM in order to use the output control function on the scan tool.

  1. Clear the DTCs using a scan tool.
  2. Install the fuel tank cap.
  3. Start and idle the engine.
  4. Command the EVAP Purge Solenoid Valve to 50% using a scan tool.
  5. Monitor the fuel tank pressure using a scan tool.

Does the Fuel Tank Pressure change when the EVAP Purge Solenoid Valve is enabled?

--

Go to Step 8

Go to Step 7

7

  1. Turn ON the ignition leaving the engine OFF.

    2. Caution: Refer to Vehicle Lifting Caution in the Preface section.

  2. Raise the vehicle. Refer to Lifting and Jacking the Vehicle in General Information.
  3. Remove the right side wheelhouse panel. Refer to Wheelhouse Panel Replacement in Body Rear End. Removing the wheelhouse panel allows access to the EVAP canister access panel.
  4. Remove the EVAP canister access panel. Removing the EVAP canister access panel allows access to the EVAP canister, hoses, pipes, and the Fuel Tank Pressure Sensor.
  5. Remove the Fuel Tank Pressure sensor from the top of the right tank. Refer to Fuel Tank Pressure Sensor Replacement .
  6. Connect the hand held vacuum pump J 23738-A to the vacuum port of the Fuel Tank Pressure sensor.
  7. Attempt to apply a vacuum up to the specified value using the hand vacuum pump J 23738-A .
  8. Monitor the Fuel Tank Pressure sensor using a scan tool.

Does the Fuel Tank Pressure sensor parameter change as vacuum is applied?

10 in Hg

Go to Step 8

Go to Step 23

8

  1. Turn OFF the ignition.
  2. Remove the EVAP Purge line from the EVAP Purge Solenoid Valve.
  3. Connect the hand held vacuum pump J 23738-A to the vacuum port of the EVAP Purge Solenoid Valve.
  4. Attempt to apply a vacuum up to the specified value using the hand vacuum pump.

Can the value specified be obtained and held?

10 in Hg

Go to Step 9

Go to Step 19

9

Important: If an audible click cannot be heard while commanding the solenoid ON and DTC P0443 is not set, inspect the EVAP Purge Solenoid Valve and circuits for high resistance.

  1. Connect a vacuum gauge to the EVAP Purge Solenoid Valve .
  2. Start the engine.
  3. Command the EVAP Purge Solenoid Valve to 50% using a scan tool.

Is the vacuum measured on the gauge the same or more than the specified value?

12 in Hg

Go to Step 11

Go to Step 10

10
  1. Turn OFF the ignition.
  2. Remove the vacuum source line from the EVAP Purge Solenoid Valve.
  3. Connect a vacuum gauge to the vacuum source.
  4. Start the engine.

Is the vacuum measured on the gauge the same or more than the specified value?

12 in Hg

Go to Step 19

Go to Step 18

11

Important: This step is to limit component removal. Access to EVAP components is difficult. Attempt to locate the leak using the Ultrasonic Leak Detector J 41416 . Place the Ultrasonic Leak Detector J 41416 as close to components as possible.

  1. Reconnect all the EVAP components.
  2. Connect the EVAP Pressure/Purge Diagnostic Station J 41413 to the EVAP system service port.
  3. Remove the right side wheelhouse panel. Refer to Wheelhouse Panel Replacement in Body Rear End. Removing the wheelhouse panel allows access to the EVAP canister access panel.
  4. Remove the EVAP canister access panel. Removing the EVAP canister access panel allows access to the EVAP canister, hoses, pipes, and the Fuel Tank Pressure Sensor.
  5. Command the EVAP Vent Valve ON (closed) using a scan tool.
  6. Continuously attempt to pressurize the EVAP system by leaving the EVAP pressure/purge diagnostic station control knob in the pressurize position.
  7. Using the Ultrasonic Leak Detector J 41416 attempt to locate a leak.
  8. If you find a condition repair as necessary.

Did you find and repair the condition?

--

Go to Step 24

Go to Step 12

12

  1. Turn OFF the ignition.
  2. Disconnect the EVAP station.

    3. Caution: Refer to Vehicle Lifting Caution in the Preface section.

  3. Raise the vehicle. Refer to Lifting and Jacking the Vehicle in General Information.
  4. Remove right side muffler assembly (automatic transmission only). Refer to Muffler Replacement in Engine Exhaust.
  5. Remove the EVAP Vent valve (near the right fuel tank) from the mounting bracket and reposition to gain access to the chassis EVAP pipe (aluminum with plastic coating). This pipe is from the EVAP Purge Solenoid Valve and goes to the EVAP canister. Refer to Evaporative Emission Vent Valve Replacement .
  6. Disconnect the chassis EVAP purge pipe (aluminum with plastic coating) at the EVAP canister nylon purge pipe. Refer to Plastic Collar Quick Connect Fitting Service .
  7. Connect the Vacuum Pump J 23738-A to the chassis EVAP Purge pipe (from the EVAP Purge Solenoid Valve ).
  8. Using the Vacuum Pump J 23738-A attempt to apply a vacuum up to the specified value.

Can the specified value of vacuum be obtained and held?

5 in Hg

Go to Step 13

Go to Step 22

13

  1. Remove the right side wheelhouse panel. Refer to Wheelhouse Panel Replacement in Body Rear End. Removing the wheelhouse panel allows access to the EVAP canister access panel.
  2. Remove the EVAP canister access panel. Removing the EVAP canister access panel allows access to the EVAP canister, hoses, pipes, and the Fuel Tank Pressure Sensor.
  3. Disconnect the fuel tank vapor line from the EVAP Canister.
  4. Plug the EVAP canister port for the fuel tank vapor line.
  5. Disconnect the EVAP purge line from the EVAP canister.
  6. Connect the Vacuum Pump J 23738-A to the EVAP Purge port on the EVAP canister.
  7. Turn ON the ignition.
  8. Command the EVAP Vent Valve ON (closed) with a scan tool.
  9. Using the Vacuum Pump J 23738-A attempt to apply a vacuum up to the specified value.

Can the specified value of vacuum be obtained and held?

5 in Hg

Go to Step 16

Go to Step 14

14
  1. Leave the system connected as in Step 13.
  2. Disconnect the vent line at the EVAP Vent Valve.
  3. Plug the vent line.
  4. Attempt to apply a vacuum up to the specified value using the Vacuum Pump J 23738-A .

Can the specified value of vacuum be obtained and held?

5 in. Hg.

Go to Step 20

Go to Step 15

15
  1. Inspect the following components for damage or leaks:
    2. • The EVAP Vent line from the canister to the EVAP Vent Valve.
    • The EVAP Canister Purge Nylon pipe (pipe from canister to chassis EVAP Purge pipe)
    • Missing/damaged O-ring seals.
  2. If you find a condition repair as necessary.

Did you find and correct the condition?

--

Go to Step 24

Go to Step 21

16

Important: Do not overlook any items which could cause a DTC to set. Inspect for the following conditions while removing the fuel tanks:

   • Loose clamps
   • Kinked lines
   • Disconnected hoses/pipes/components
   • Damaged hoses/pipes/components
   • Damaged or missing O ring seals

  1. Remove the left side fuel tank. Refer to Fuel Tank Replacement .
  2. Remove the right side fuel tank. Refer to Fuel Tank Replacement .
  3. Perform the Fuel Tank Leak test. Refer to Fuel Tank Leak Check .

Did you find and correct the condition?

--

Go to Step 24

Go to Step 17

17

  1. Inspect all EVAP system components/pipes for restrictions. Refer to Evaporative Emission Control System Operation Description .
  2. Repair condition as necessary.

Did you find and correct the condition?

--

Go to Step 24

Go to Step 2

18

Repair the vacuum source to the EVAP Purge Solenoid Valve.

Is the action complete?

--

Go to Step 24

--

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. Refer to Evaporative Emission Canister Purge Solenoid Valve Replacement .

Is the action complete?

--

Go to Step 24

--

20

Replace the EVAP Vent Valve. Refer to Evaporative Emission Vent Valve Replacement .

Is the action complete?

--

Go to Step 24

--

21

Replace the EVAP Vapor Canister. Refer to Evaporative Emission Canister Replacement .

Is the action complete?

--

Go to Step 24

--

22

Replace the EVAP line from the EVAP Purge Solenoid Valve to the EVAP canister as necessary. Refer to Fuel Hose/Pipes Replacement - Chassis .

Is the action complete?

--

Go to Step 24

--

23

Replace the Fuel Tank Pressure sensor. Refer to Fuel Tank Pressure Sensor Replacement .

Is the action complete?

--

Go to Step 24

--

24

Important: Ensure that The Conditions for Running the Service Bay test are met before proceeding with this diagnostic. Refer to Diagnostic Aids.

Perform the EVAP system Service Bay Test using a scan tool.

Does the EVAP diagnostic pass the Service Bay Test?

--

Go to Step 25

Go to Step 5

25

Select the Capture Info option and the Review Info option using the scan tool.

Does the scan tool display any DTCs that you have not diagnosed?

--

Go to Applicable DTC

System OK