GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2002 🢒 Envoy - 4WD 🢒 Engine 🢒 Engine Controls - 4.2L 🢒 DTC P0442

System Description

The evaporative emission (EVAP) small leak test applies vacuum to the EVAP system and monitors vacuum decay. The powertrain control module (PCM) monitors the fuel tank pressure (FTP) sensor signal to determine the vacuum decay rate. At an appropriate time, the PCM 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 PCM 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.

Conditions for Running the DTC
    • DTCs P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0125, P0440, 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.

Conditions For Setting the DTC

The EVAP system is not able to maintain vacuum during the diagnostic test.

Action Taken When the DTC Sets
    • The PCM will illuminate the malfunction indicator lamp (MIL) during the second consecutive trip in which the diagnostic test ran and failed.
    • The PCM will store conditions which were present when the DTC set as Freeze Frame/Failure Records data.

Conditions for Clearing the MIL/DTC
    • The PCM will turn the MIL OFF during the first consecutive trip in which the diagnostic has been run and passed.
    • A last test failed (current DTC) clears when the PCM turns OFF the MIL.
    • The history DTC will clear after the PCM runs and passes 40 consecutive warm up cycles with no failure.
    • The DTC can be cleared by using a scan tool.

Diagnostic Aids

Important: If carbon release is detected, refer to Evaporative Emission System Cleaning .

Reviewing the Failure 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.

To aid in locating an intermittent leak, use the J 41413 EVAP Pressure/Purge Diagnostic Station to pressurize the EVAP system. Move all EVAP system components while testing with the J 41416 Ultrasonic Leak Detector.

Test Description

The number below refers to the step number on the diagnostic table.

  1. This step verifies the repairs that have been made.

Step

Action

Values

Yes

No

Schematic Reference: Evaporative Emissions Hose Routing Diagram

1

Did you perform the Diagnostic System Check-Engine Controls?

--

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

Are DTCs P0440, P0446, P0452, P0453, or P1442 also set?

--

Go to Diagnostic Trouble Code (DTC) List

Go to Step 3

3

Inspect the EVAP system for the following conditions:

    • A loose, incorrect, faulty, or missing fuel tank fill cap
    • Damaged or disconnected EVAP system purge lines
    • A damaged EVAP system component
    • A loose, missing, or damaged service port schrader valve

Did you find and correct the condition?

--

Go to Step 6

Go to Step 4

4

Important: The following steps require the J 41413 EVAP Pressure/Purge Diagnostic Station and the J 41415-40 Fuel Tank Cap Adaptor.

Always zero the EVAP pressure and vacuum (in H2O) gages on the EVAP pressure/purge diagnostic station before proceeding with diagnosis.

  1. Install the fuel tank cap adaptor.
  2. Connect the EVAP pressure/purge diagnostic station and the fuel tank cap to the fuel tank cap adaptor.
  3. Turn ON the ignition, with the engine OFF.
  4. Use a scan tool to clear the DTCs from the PCM.
  5. Command the EVAP vent valve ON with a scan tool.
  6. Pressurize the EVAP system to the specified value with the EVAP pressure/purge diagnostic station.
  7. Place the control knob on the EVAP pressure/purge diagnostic station to the OFF/HOLD position.
  8. Monitor the EVAP system pressure on the EVAP pressure/purge diagnostic station for 5 minutes.

Does the EVAP system pressure remain constant?

5 in H2O

Go to Diagnostic Aids

Go to Step 5

5
  1. With the pressure/purge diagnostic station, continuously attempt to pressurize the EVAP system.

    2. Important: It may be necessary to partially lower the fuel tank to inspect components located in the upper portion of the tank.

  2. With the J 41416 ultrasonic leak detector inspect for leaks in the following locations:
    3. • The EVAP system purge pipe--Refer to Evaporative Emission Hoses/Pipes Replacement - Engine/Chassis .
    • The fuel fill pipe/hose and fuel fill cap--Refer to Fuel Tank Filler Hose Replacement .
    • The EVAP canister--Refer to Evaporative Emission Canister Replacement .
    • The EVAP canister vent valve--Refer to Evaporative Emission Canister Vent Solenoid Valve Replacement .
    • The EVAP canister purge valve--Refer to Evaporative Emission Canister Purge Solenoid Valve Replacement .
    • The fuel sender assembly and/or seal--Refer to Fuel Sender Assembly Replacement .
    • The FTP sensor seal--Refer to Fuel Tank Pressure Sensor Replacement .
    • The fill limiter vent valve, pressure relief valve, rollover valves, and fuel tank--Refer to Fuel Tank Replacement .

Did you find and repair the condition?

--

Go to Step 6

Go to Diagnostic Aids

6

  1. Turn ON the ignition, with the engine OFF.
  2. With a scan tool, clear the DTCs.
  3. Command the EVAP vent valve ON with a scan tool.
  4. Pressurize the EVAP system to the specified value with the EVAP pressure/purge diagnostic station.
  5. Place the control knob on the EVAP pressure/purge diagnostic station to the OFF/HOLD position.
  6. Monitor the EVAP system pressure on the EVAP pressure/purge diagnostic station for 5 minutes.

Does the EVAP system pressure remain constant?

--

Go to Step 7

Go to Step 2

7

With a scan tool, observe the stored information, Capture Info.

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

--

Go to Diagnostic Trouble Code (DTC) List

System OK