GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2002 🢒 Yukon XL - 2WD 🢒 Engine 🢒 Engine Controls - 4.8L, 5.3L, and 6.0L 🢒 DTC P0440

System Description

The control module tests the evaporative emission (EVAP) system for a large leak. The control module monitors the fuel tank pressure (FTP) sensor signal to determine the EVAP system vacuum level. When the conditions for running are met, the control module commands the EVAP canister purge valve OPEN and the EVAP vent valve CLOSED . This allows engine vacuum to enter the EVAP system. At a calibrated time, or vacuum level, the control module commands the EVAP canister purge valve closed, sealing the system, and monitors the FTP sensor input in order to determine the EVAP system vacuum level. If the system is unable to achieve the calibrated vacuum level, or the vacuum level decreases too rapidly, 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, P0115, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0443, P0449, P0452, P0453, P1106, P1107, P1112, P1114, P1115, P1121 or P1122 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.
    • The vehicle speed sensor (VSS) is less than 121 km/h (72.8 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) on the second consecutive ignition cycle that the diagnostic runs and fails.
    • The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

Conditions for Clearing the MIL/DTC
    • The control module will turn the malfunction indicator lamp (MIL) OFF during the first consecutive trip in which the diagnostic has been run and passed.
    • A current DTC, Last Test Failed, clears when the control module turns OFF the MIL.
    • The history DTC will clear after the control module runs and passes 40 consecutive warm up cycles with no failure.
    • Use the scan tool in order to clear the DTC.

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 to verify if a leak is present.

    3.

  3. This step verifies proper operation of the FTP sensor.

    4.

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

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

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 17

Go to Step 4

4

  1. With a scan tool, capture and record the Failure 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 the J 41415 Fuel Fill Cap Adaptor

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 .
  2. Connect the pressure/purge diagnostic station to the J 41413 .
  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 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 Diagnostic Aids

Go to Step 9

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 following locations:
    3. • The EVAP system purge pipe--Refer to Evaporative Emission System Hoses/Pipes Replacement .
    • The EVAP vapor pipe--Refer to Evaporative Emission System Hoses/Pipes Replacement .
    • The EVAP vent hose/pipe--Refer to Evaporative Emission System Hoses/Pipes Replacement .
    • The fuel fill pipe/hose and fuel fill cap.
    • 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, permanent EVAP pipes and/or fuel tank--Refer to Fuel Tank Replacement .
    • If equipped with a rear tank, the rear fuel sender assembly and/or seal--Refer to Fuel Sender Assembly Replacement .
    • If equipped with a rear tank, the rollover valves, EVAP pipes and/or rear fuel tank--Refer to Fuel Tank Replacement .
    • If equipped with a rear tank, the fuel transfer pipe.

Did you locate and repair a leak?

--

Go to Step 18

Go to Diagnostic Aids

9

  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 14

Go to Step 10

10
  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 Step 15

Go to Step 11

11
  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 16

Go to Step 13

12

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

Did you complete the replacement?

--

Go to Step 17

--

13

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

Did you complete the repair?

--

Go to Step 17

--

14

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

Did you complete the replacement?

--

Go to Step 17

--

15

Repair the restriction in the EVAP purge pipe. Refer to Evaporative Emission System Cleaning .

Did you complete the repair?

--

Go to Step 17

--

16

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

Did you complete the replacement.

--

Go to Step 17

--

17

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

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

--

Go to Step 18

Go to Step 5

18

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