GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2001 🢒 Firebird 🢒 Body and Accessories 🢒 Body Control System 🢒 DTC P0442

System Description

This DTC tests the evaporative emission (EVAP) system for a small leak. 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 and the EVAP vent valve ON. This allows the engine to draw a vacuum on the EVAP system. At a calibrated time, or vacuum level, the control module turns the EVAP canister purge valve OFF, sealing the system, and monitors the FTP sensor input in order to determine the EVAP system vacuum decay. If the control module detects a leak larger than a calibrated amount, this DTC sets.

The following table illustrates the relationship between the ON and OFF states, and the Open or Closed states of the EVAP canister purge and vent valves.

Control Module Command

EVAP Canister Purge Valve

EVAP Canister Vent Valve

ON

Open

Closed

OFF

Closed

Open

Conditions for Running the DTC
    • DTCs P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0125, P0440, P0443, P0449, P0452, P0453, P1106, P1107, P1112, P1114, P1120, P1220, or P1221 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 can achieve vacuum, but a vacuum decay is detected during the diagnostic test.

Action Taken When the DTC Sets
    • The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
    • The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.

Conditions for Clearing the MIL/DTC
    • 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.

Diagnostic Aids

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

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. This step verifies that a leak is present.

    2.

  2. This step verifies that repairs are complete and that there are no other leaks in the system.

Step

Action

Values

Yes

No

Schematic Reference: Evaporative Emissions Hose Routing Diagram

1

Did you perform the Diagnostic System Check-Engine Controls?

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Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

Does the scan tool indicate that DTCs P0443, P0446, P0449, P0452, P0453, P0461, P0462, P0463, or P1441 are also set?

--

Go to Diagnostic Trouble Code (DTC) List

Go to Step 3

3
  1. Inspect the evaporative emission (EVAP) system for the following conditions:
    2. • Loose, missing, or damaged service port dust cap and/or schrader valve
    • Loose, incorrect, missing, or damaged fuel fill cap
    • A damaged EVAP canister purge valve
  2. Raise the vehicle on a hoist. Refer to Lifting and Jacking the Vehicle in General Information.
  3. Inspect the EVAP system for the following conditions:
    4. • Disconnected, improperly routed, kinked, or damaged EVAP pipes and hoses
    • A damaged EVAP canister vent valve or EVAP canister

Did you find and correct the condition?

--

Go to Step 5

Go to Step 4

4

Important: Always zero the EVAP pressure and vacuum -- in H2O, gages on the EVAP pressure/purge diagnostic station before proceeding with diagnosis.

  1. Install the J 41415 Fuel Tank Cap Adaptor.
  2. Connect the J 41413 EVAP Pressure/Purge Diagnostic Station and the fuel tank cap to the J 41415 .
  3. Turn ON the ignition, with the engine OFF.
  4. With the scan tool, seal the EVAP system.
  5. With the J 41413 , continuously pressurize the EVAP system to the specified value.

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

  6. With the J 41416 Ultrasonic Leak Detector, inspect for leaks in the following locations:
    7. • 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 Filler Tube 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 Tank Pressure Sensor Replacement .
    • The fuel tank pressure (FTP) sensor seal--Refer to Fuel Tank Pressure Sensor Replacement .
    • The fill limiter vent valve, pressure relief valve, rollover valve, or fuel tank--Refer to Fuel Tank Replacement .

Did you find and correct the condition?

15 in H2O

Go to Step 5

Go to Diagnostic Aids

5

  1. Remove and then reinstall the fuel fill cap to relieve the fuel tank pressure.
  2. Turn ON the ignition, with the engine OFF.
  3. Command the EVAP canister vent valve ON with a scan tool.
  4. Pressurize the EVAP system to the specified value with the J 41413 .
  5. Place the control knob on the J 41413 to the OFF/HOLD position.
  6. Monitor the EVAP system pressure on the J 41413 for 5 minutes.

Does the EVAP system pressure remain constant?

5 in H2O

Go to Step 6

Go to Step 4

6

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

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

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Go to Diagnostic Trouble Code (DTC) List

System OK