GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2001 🢒 Yukon XL - 4WD 🢒 Engine 🢒 Engine Controls - 8.1L 🢒 DTC P0440

Description

The EVAP LARGE LEAK TEST is based on applying vacuum to the evaporative emission (EVAP) system and monitoring the rate of vacuum decay. The powertrain control module (PCM) uses the input from the fuel tank pressure (FTP) sensor in order to determine the rate of vacuum decay. At an appropriate time, the PCM turns the EVAP canister purge valve ON (open) and the EVAP canister vent valve ON (closed). This allows the engine to draw a vacuum on the system. At a calibrated time or vacuum level, the PCM turns the purge valve OFF (closed), and tests the system vacuum. If the system is unable to achieve the calibrated vacuum level, the PCM will set DTC P0440.

Conditions for Running the DTC
    • DTCs P0107, P0108, P0112, P0113, P0117, P0118, P0443, P0449, P0452, P0453, P1111, P1112, P1114, P1115, P1120, P1220 or P1221 are not set.
    • The system voltage is between 10-18 volts.
    • The startup (ECT) engine coolant temperature is between than 4-30°C (39-86°F), but the start up ECT is not more than 8°C (14°F) more than the startup intake air temperature (IAT) temperature.
    • The startup (IAT) intake air temperature is between than 4-30°C (39-86°F), but the start up IAT is not more than 3°C (7°F) more than the startup ECT temperature.
    • The fuel tank level is between 15-85 percent.
    • The barometric pressure (BARO) is more than 75 kPa.
    • The vehicle speed sensor (VSS) is less than 120.7 km/h (75 mph).

Conditions For Setting the DTC

The EVAP system is not able to achieve or maintain vacuum 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
    •  Use the J 41413 EVAP Pressure/Purge Diagnostic Station in order to pressurize the EVAP system to aid in locating intermittent leaks.
    •  Move all EVAP components while testing with the J 41416 Ultrasonic Leak Detector.
    • A temporary blockage in the EVAP canister purge valve, purge pipe or EVAP canister could cause an intermittent condition. To repair a blockage in the EVAP system, refer to Evaporative Emission System Cleaning .

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 is used in order to verify if a leak is present.

    3.

  3. This step verifies proper operation of the fuel tank pressure (FTP) sensor.

    4.

  4. This step tests the EVAP canister purge valve for a restriction or blockage.

    5.

  5. 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

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 19

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: The following steps require the J 41413 EVAP Pressure/Purge Diagnostic Station and theJ 41415 Fuel Fill Cap Adaptor .

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

  1. Install the J 41415 .
  2. Connect the J 41413 Gas Cap Filler Neck Kit.
  3. Turn ON the ignition, with the engine OFF.
  4. With the scan tool, seal the EVAP system.
  5. With the EVAP pressure/purge diagnostic station, pressurize the system to the specified value.
  6. Rotate the EVAP pressure/purge diagnostic station rotary switch to the OFF/HOLD position.

Did you obtain the specified value?

5 in. H2O

Go to Step 6

Go to Step 8

6

Compare the EVAP pressure/purge diagnostic station value to the scan tool fuel tank pressure (FTP) sensor value.

Does EVAP pressure/purge diagnostic station value measure near the scan tool value?

--

Go to Step 7

Go to Step 14

7
  1. With the pressure/purge diagnostic station, maintain EVAP system pressure at the specified value.
  2. Monitor the pressure gauge on EVAP pressure/purge diagnostic station.
  3. With a scan tool, command the EVAP canister purge valve to 50 percent.

Does the EVAP system pressure decrease?

5 in. H2O

Go to Step 10

Go to Step 11

8
  1. With the pressure/purge diagnostic station, continuously 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 Fuel or EVAP Systems.

Did you locate a leak?

--

Go to Step 9

Go to Diagnostic Aids

9

Repair the system as necessary.

Did you complete the repair?

--

Go to Step 19

--

10

  1. Disconnect the EVAP purge pipe from the EVAP canister purge valve.
  2. Install the EVAP pressure/purge diagnostic station vacuum hose on the EVAP canister purge valve port.
  3. Start the engine.
  4. Run the engine between 1,200-1,500 RPM.
  5. With a scan tool command the EVAP canister purge valve to 50 percent.

Does the EVAP pressure/purge diagnostic station vacuum gauge measure above the specified value?

12  in. Hg

Go to Diagnostic Aids

Go to Step 16

11
  1. Monitor the pressure gauge on EVAP pressure/purge diagnostic station.
  2. Disconnect the EVAP purge pipe from the EVAP canister purge valve.

Does the EVAP system pressure decrease?

--

Go to Step 17

Go to Step 12

12
  1. Monitor the pressure gauge on EVAP pressure/purge diagnostic station.
  2. Disconnect the purge pipe at the EVAP canister.

Does the EVAP system pressure decrease?

--

Go to Evaporative Emission System Cleaning

Go to Step 13

13
  1. Monitor the pressure gauge on EVAP pressure/purge diagnostic station.
  2. Disconnect the EVAP vapor line from the EVAP canister.

Does the EVAP system pressure decrease?

--

Go to Step 18

Go to Step 15

14

Replace the (FTP) fuel tank pressure sensor. Refer to Fuel Tank Pressure Sensor Replacement .

Did you complete the replacement?

--

Go to Step 19

--

15

Repair the pinched or obstructed EVAP vapor pipe between the front and rear tanks.

Did you complete the repair?

--

Go to Step 19

--

16

Repair the plugged vacuum supply.

Did you find and correct the condition?

--

Go to Step 19

Go to Step 17

17

Replace the EVAP canister purge valve. Refer to Evaporative Emission Canister Purge Solenoid Valve Replacement .

Did you complete the replacement?

--

Go to Step 19

--

18

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

Did you complete the replacement?

--

Go to Step 19

--

19

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

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

--

Go to Step 20

Go to Step 2

20

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