GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2001 🢒 Express 🢒 Engine 🢒 Engine Controls - 4.3L 🢒 DTC P0442

Description

The EVAP small leak test is based on applying vacuum to the evaporative emission (EVAP) system and monitoring vacuum decay. This diagnosis will detect a leak as small as 0 .040 inch in the EVAP system. The powertrain control module (PCM) monitors vacuum level via the fuel tank pressure (FTP) sensor input. At an appropriate time, the EVAP canister purge valve and the EVAP vent valve are turned ON. This allows the engine to draw a small vacuum on the entire evaporative emission system. After the desired vacuum level has been achieved, the EVAP purge valve is turned OFF, sealing the system. A leak is detected by monitoring for a decrease in the vacuum level during a given time period. A small leak in the system will cause DTC P0442 to be set.

Conditions for Running the DTC
    • DTCs P0107, P0108, P0110, P0112, P0113, P0115, P0117, P0118, P0121, P0122, P0123, P0125, P0440, P0443, P0449, P0452, P0453, P1106, P1107, P1111, P1112, P1114, P1115, P1121, or P1122 are not active.
    • The system voltage is between 10-18 volts.
    • The startup engine coolant temperature (ECT) is between 4-30°C (39-86°F), but the startup ECT is not more than 8°C (46°F) more than the startup IAT temperature.
    • The startup intake air temperature (IAT) is between 4-30°C (39-86°F), but the startup IAT not more than 3°C (37°F) more than the startup ECT temperature.
    • The fuel tank level is between 20-85 percent.
    • The barometric pressure (BARO) is more than 75 kPa.
    • The vehicle speed sensor (VSS) is less than 121 km/h (75 mph).

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

The EVAP system tests run when the engine is first started and meets the Conditions for Running the DTC. To aid in locating intermittent leaks, use the 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 failure condition is active.

    2.

  2. This step verifies that repairs are complete and that no other condition is present.

Step

Action

Values

Yes

No

Schematic Reference: Emission Hose Routing Diagram and Engine Controls Schematics

1

Did you perform the Diagnostic System Check-Engine Controls?

--

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

Does the scan tool indicate DTC P0443 or DTC P0449 are also set?

--

Go to Diagnostic Trouble Code (DTC) List

Go to Step 3

3
  1. Inspect the 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 6

Go to Step 4

4

  1. With a scan tool, capture and record the fail record data and clear the DTCs.
  2. Perform the Service Bay Test. Refer to Service Bay Test .

Does the scan tool indicate that the service bay test passed?

--

Go to Diagnostic Aids

Go to Step 5

5

Important: Always zero the EVAP Pressure and vacuum (in. H2O) gauges on the EVAP Pressure Diagnostic Station before proceeding with diagnosis.

  1. Install the J 41415 Fuel Fill Cap Adaptor.
  2. Connect the J 41413 Pressure/Purge Diagnostic Station to the fuel fill cap adaptor.
  3. Turn ON the ignition, with the engine OFF.
  4. With the scan tool, seal the EVAP system.
  5. With the pressure/purge diagnostic station, 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 .
    • The EVAP vapor pipe--Refer to Fuel Tank Replacement .
    • The EVAP vent hose.
    • 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 sea--Refer to Fuel Sender Assembly Replacement .
    • The fuel tank pressure (FTP) sensor seal--Refer to Fuel Tank Pressure Sensor Replacement .
    • The fill limiter vent valve, pressure relief valve, rollover valves, permanent EVAP pipes and/or fuel tank--Refer to Fuel Tank Replacement .

Did you find and correct the condition?

15 in H2O

Go to Step 6

Go To Diagnostic Aids

6

Perform the Service Bay Test. Refer to Service Bay Test .

Does the scan tool indicate that the service bay test passed?

--

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