DTC P0440 Evaporative Emission (EVAP) System. Buick Skylark 1998

For 1990-2009 cars only

Makes 🢒 Buick 🢒 1998 🢒 Skylark 🢒 Engine 🢒 Engine Controls - 3.1L 🢒 DTC P0440 Evaporative Emission (EVAP) System

Refer to

EVAP Control System Overview


(1)	EVAP Vent Valve/Solenoid
(2)	EVAP Vent Valve/Solenoid Ignition Feed Circuit Terminal
(3)	EVAP Vent Valve/Solenoid Control Circuit Terminal
(4)	EVAP Vent Valve/Solenoid Filter
(5)	EVAP Vapor Lines
(6)	Fuel Tank Pressure Sensor
(7)	Fuel Tank Pressure Sensor Ground Circuit Terminal
(8)	Fuel Tank Pressure Sensor Signal Circuit Terminal
(9)	Fuel Tank Pressure Sensor Circuit 5 Volt Reference Circuit Terminal
(10)	Fuel Filler Pipe
(11)	Check Valve (Spitback)
(12)	Modular Fuel Sender Assembly
(13)	Fuel Limiter Vent Valve (FLVV)
(14)	Pressure/Vacuum Relief Valve (Optional)
(15)	EVAP Canister
(16)	EVAP Canister Purge Valve/Solenoid Ignition Feed Circuit Terminal
(17)	EVAP Canister Purge Valve/Solenoid Control Circuit Terminal
(18)	Intake Manifold Vacuum Source
(19)	EVAP Canister Purge Valve/Solenoid
(20)	EVAP Service Port

EVAP System Description

The evaporative system includes the following components:

•	The fuel tank.

•	The EVAP vent valve/solenoid.

•	The fuel tank pressure sensor.

•	The fuel pipes and hoses.

•	The fuel fill cap.

•	The EVAP vapor lines.

•	The EVAP purge lines.

•	The EVAP canister.

•	The EVAP canister purge valve/solenoid.

The EVAP LARGE LEAK TEST Is based on applying vacuum to the EVAP system and monitoring vacuum decay. The PCM monitors vacuum level via the Fuel Tank Pressure Sensor input. At an appropriate time, the EVAP canister purge valve/solenoid and the EVAP vent valve/solenoid are turned on, allowing engine vacuum to draw a small vacuum on the entire evaporative emission system. If a sufficient vacuum level cannot be achieved, a large leak or a faulty EVAP canister purge valve/solenoid is indicated. This can caused by the following conditions:

•	Disconnected or faulty fuel tank pressure sensor.

•	Missing, not completely installed or faulty fuel fill cap.

•	Disconnected, damaged, pinched, or blocked EVAP purge line.

•	Disconnected or damaged EVAP vent hose.

•	Disconnected, damaged, pinched, or blocked fuel tank vapor line.

•	Disconnected or faulty EVAP canister purge valve/solenoid.

•	Disconnected or faulty EVAP vent valve/solenoid.

•	Open ignition feed circuit to the EVAP vent or purge valve/solenoid.

•	Damaged EVAP canister.

•	Leaking fuel sender assembly O-ring.

•	Leaking fuel tank or fuel filler neck

Any of the above conditions can set DTC P0440.

Conditions for Running the DTC

•	No TP sensor, ODM, IAT sensor, or MAP sensor DTCs set.

•	System voltage is between 9 and 16 volts.

•	Startup engine coolant temperature is between 4°C and 30°C (40°F and 86°F).

•	Startup engine coolant temperature is not more than 8°C (14°F) greater than startup intake air temperature.

•	Startup Intake air temperature is between 4°C and 30°C (40°F and 86°F).

•	Startup intake air temperature not more than 2°C (4°F) greater than start-up engine coolant temperature.

•	Fuel tank level is between 15% and 85%.

•	BARO is greater than 75kPa.

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

Important: Although this diagnostic is considered type A, it acts like a type B diagnostic. Whenever the EVAP diagnostics report that a system has passed, or if the battery has been disconnected, the diagnostic must fail during 2 consecutive cold start trips before setting a DTC. The initial failure is not reported to the diagnostic executive or displayed on a scan tool. A passing system always reports to the diagnostic executive immediately.

•	The PCM will store conditions which were present when the DTC set as Freeze Frame data.

•	The PCM will store conditions which were present when the DTC set as Fail Records data.

Conditions for Clearing the MIL/DTC

•	The PCM will turn the MIL OFF when the diagnostic has been run and the fault condition is no longer present.

•	A history DTC P0440 will clear after 40 consecutive warm-up cycles have occurred without a fault.

•	This DTC can be cleared by using the scan tool Clear Info function or by disconnecting the PCM battery feed.

•	The code will clear if the fill cap is tightened or Reinstalled.

Diagnostic Aids

Check for the following conditions:

•	Cracked or punctured EVAP canister.

•	Damaged or disconnected source vacuum line, EVAP purge line, vent hose or fuel tank vapor line.

•	Poor connection at the PCM.

•	Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection.

•	Damaged harness. Inspect the wiring harness to the EVAP vent valve/solenoid, the EVAP purge valve/solenoid, and the fuel tank pressure sensor for an intermittent open or short circuit.

•	Kinked, pinched or plugged vacuum source, EVAP purge, or fuel tank vapor line. Verify that the lines are not restricted.

•	Use the following procedure to check for a carbon release condition that could plug the system.

1.	Turn off the ignition switch.

2.	Remove the EVAP canister purge valve/solenoid. Refer to Evaporative Emission Canister Purge Solenoid Valve Replacement .

3.	Lightly tap the canister purge valve on a clean work area looking for carbon particles exiting either of the vacuum ports.

4.	If no carbon release is evident, reinstall the components and continue with the DTC P0440 diagnostic table. If carbon is being released from either component, continue with this service procedure.

5.	Remove the charcoal canister from the vehicle.

Ensure that the main cylinder valve is turned off on the
Object Number: 20803 Size: SH


(1)	Main Valve
(2)	Evaporative Emission System Purge/Presure Diagnostic Station J 41413
(3)	Nitrogen Cylinder
(4)	Black Connecting Hose
(5)	Threaded Fitting
(6)	Gauge Set

EVAP purge/pressure diagnostic station.

7.	Disconnect the black hose that connects the nitrogen cylinder to the EVAP purge/pressure diagnostic station at the pressure regulator by unscrewing the knurled nut on the regulator. No tools are required to remove the black hose from the regulator.

8.	Using a section of vacuum line, connect one end over the open threaded fitting of the EVAP purge/pressure diagnostic station pressure regulator.

9.	Connect the remaining end to the purge valve end of the EVAP purge line at the vehicle and turn on the main nitrogen cylinder valve. Continue to blow any debris from the purge line for 15 seconds.

10.	Return the EVAP Pressure/Purge Diagnostic Station to its original condition by reinstalling the black hose that was disconnected in step 7.

11.	Replace the following components:

•	The EVAP canister purge valve. Refer to Evaporative Emission Canister Purge Solenoid Valve Replacement .

•	The EVAP canister. Refer to Evaporative Emission Canister Replacement EVAP Canister.

12.	Proceed with the DTC P0440 diagnostic table.

Reviewing the Fail 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.

Test Description

Number(s) below refer to the step number(s) on the Diagnostic Table:

The powertrain OBD System Check prompts you to complete some of the basic checks and store the freeze frame and failure records data on the Scan Tool if applicable.

If a vent valve or EVAP purge valve electrical malfunction is present, the purge system will not operate correctly. Repairing the electrical malfunction that caused the additional DTC to set will very likely correct the condition that set this DTC.

Checks for a fuel tank pressure sensor stuck high condition. The fuel tank pressure must be relieved by removing the canister line from the fuel tank or EVAP canister. The fuel fill cap will not relieve the fuel tank pressure due to a check valve in the filler neck. The check valve seals when pressure is applied to prevent vapors from escaping through the filler neck. The Scan Tool should read within +/- 1.0 in H2O of the specified value.

Checks for a Large Leak in the EVAP system.

Verifies that the fuel tank pressure sensor accurately reacts to EVAP system pressure changes. The EVAP station is pressurizing a sensor that normally reads vacuum. The tech II reads high pressure at 0 volts and high vacuum at 5 volts. the Tech II can only read a max pressure of 6.0 inches of H2O (0 Volts). However the EVAP Service station can pressurize the system to much higher pressures. The Scan Tool value should be within +/- 0.5 of the specified value.

Checks for a leaking EVAP canister line, or vent valve.

Checks for a stuck closed or plugged EVAP canister purge valve/solenoid

Checks for a leaking or stuck open EVAP canister purge valve/solenoid, The scan tool should read within +/- 1.0 in HG of the specified value.

Checks for a leaking or stuck open EVAP canister purge valve/solenoid. The valve should be within +/- 1.0 in HG of the specified value.

Ensures that sufficient source vacuum is present at the EVAP canister purge valve/solenoid.

The EVAP station is pressurizing a sensor that normally reads vacuum. The Tech II reads high pressure at 0 volts and high vacuum at 5 volts. The Tech II can only read a max pressure of 6.0 inches of H2O (0 Volts). However the EVAP Service station can pressurize the system to much higher pressures. The Scan Tool value should be within +/- 0.5 of the specified value.

DTC P0440 - EVAP System

Step

Action

Value(s)

Yes

Was the Powertrain OBD System Check performed?

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

Visually/physically inspect for the following conditions:

•	Vacuum or purge lines disconnected. Refer to Emission Hose Routing Diagram .

•	Loose or missing fuel fill cap.

Is DTC P1665 Evaporative Emission (EVAP) Vent Solenoid Control Circuit or DTC P1676 Evaporative Emission (EVAP) Purge Solenoid Control Circuit also set?

Go to DTC P1665 Evaporative Emission (EVAP) Vent Solenoid Control Circuit or DTC P1676 Evaporative Emission (EVAP) Purge Solenoid Control Circuit

Go to Step 3

Ignition Switch OFF.
Remove the canister purge line from the EVAP canister purge valve.
Ignition switch ON, Engine OFF.
Observe Fuel Tank Pressure on the scan tool.

Is the Fuel Tank Pressure near the specified value?

0 in H2O

Go to Step 4

Go to Step 19

Important: : Before continuing with diagnosis, zero the EVAP Pressure and Vacuum (inches of H2O) gauges on the J 41413 .

Important:: Do not exceed the pressure in the specified value .

Ignition Switch OFF.
Reconnect all EVAP hardware that was previously disconnected.
Install the J 41415-40 Fill Tank Cap Adaptor to the fuel fill neck and fuel fill cap.
Connect the EVAP station to the fuel tank cap Adaptor.
Ignition Switch ON, Engine OFF.
Capture Fail Record data for DTC P0440 and clear DTCs.
Using the scan tool, EVAP Purge/Seal, select seal option to seal the EVAP System.
Attempt to pressurize the system to the specified value by slowly turning the EVAP Service Station rotary switch to the pressure position (monitor the pressure with the gauge on the cart with the rotary switch in the Off/Hold position).

Can specified value be achieved?

5 in H2O

Go to Step 5

Go to Step 6

Maintain the Fuel Tank Pressure at the specified value (monitor the pressure with the gauge on the cart with the rotary switch in the Off/Hold position).
Observe Fuel Tank Pressure on the scan tool.

Is the Fuel Tank Pressure near the specified value?

5 in H2O

Go to Step 8

Go to Step 7

Disconnect the fuel tank vapor line and the EVAP purge line from the EVAP canister.
Block the canister fitting for the fuel tank vapor line.
Connect a J 23738-A hand vacuum pump to the canister port for the EVAP purge line.
Ensure that the EVAP System is still sealed with the tech II. This seals off the fresh air inlet to the canister.
Attempt to apply vacuum to the EVAP canister. The EVAP canister is large and may take time to achieve specified level.

Can vacuum be maintained at the specified value?

5 in Hg

Go to Step 11

Go to Step 10

Visually/physically check for the following conditions:

•	Restricted fuel tank vapor line.

•	Restricted EVAP purge line.

If a problem is found, repair as necessary.

Was a problem found?

Go to Step 20

Go to DTC P0452 Fuel Tank Pressure Sensor Circuit Low Voltage

Maintain the Fuel Tank Pressure at the first specified (higher) value (monitor the pressure with the gauge an the cart with the rotary switch in the Off/Hold position.
Using the Scan Tool, increase the purge to 100% This should relieve the system pressure through the purge valve.

Does the EVAP pressure decrease to within +/- 1.0 of the second specified (lower) value within 15 seconds?

5 in H2O

0 in H2O

Go to Step 9

Go to Step 14

Connect the in. Hg vacuum gauge on the EVAP Service Station to the purge valve/solenoid, canister side.
Ignition switch ON, Engine OFF.
Using the Scan Tool, EVAP Purge/seal, select the seal option to seal the EVAP System.
Start the engine and idle.
Run the engine from 1200 -1500 RPM and observe vacuum level.

Is vacuum level near the specified value?

0 in Hg

Go to Step 17

Go to Step 14

Visually/physically check for the following conditions:

•	Disconnected or damaged Fresh Air Vent Hose.

•	Damaged EVAP canister .

If a problem is found, repair as necessary.

Was a problem found?

Go to Step 20

Go to Step 16

Visually/physically check for the following conditions:

•	Disconnected or leaking fuel tank vapor line.

•	Disconnected or damaged EVAP purge line.

If a problem is found, repair as necessary.

Was a problem found?

Go to Step 20

Go to Step 12

Disconnect the engine vacuum Purge line from the EVAP canister purge valve.
Connect the EVAP Service Station (Hg) Vacuum Gauge to the Purge Valve/Solenoid, canister side.
Ignition switch ON, Engine Off.
Using the Scan Tool, EVAP purge/seal, select the seal option to seal the EVAP system.
Start the engine and idle.
Run the engine from 1200 -1500 RPM and observe vacuum level.

Is vacuum level near the specified value?

0 in. Hg

Go to Step 13

Go to Step 14

Important: Do not exceed the pressure in the specified value.

Reconnect all EVAP hardware that was previously disconnected.
Ignition switch On, Engine Off.
Using the scan tool, EVAP purge/seal, select the seal option to seal the EVAP system.
With the EVAP pressure/purge diagnostic station connected to the EVAP service port, continuously attempt to pressurize the EVAP system to the specified value by leaving the EVAP pressure/purge diagnostic station control knob in the pressurize position
Using the J 41416 ultrasonic leak detector, locate and repair leak in EVAP system. It may be necessary to partially lower the fuel tank to examine the top tank connections.
Replace the faulty part(s).

Is the action complete?

5 in H2O

Go to Step 20

Important: : Check for carbon release into the EVAP system. Refer to Diagnostic Aids.

Replace the EVAP Canister Purge Valve/Solenoid. Refer to Evaporative Emission Canister Purge Solenoid Valve Replacement .

Is the action complete?

Go to Step 20

Check for no source vacuum to the EVAP purge valve.
If problem was found repair as necessary

Was a problem Found?

Go to Step 20

Go to Step 14

Replace the EVAP Vent Valve/Solenoid. Refer to Evaporative Emission Vent Valve Replacement .

Is the action complete?

Go to Step 20

Using the Scan Tool, increase Purge to 100%.
Run the engine from 1200-1500 RPM and observe vacuum level.

Is vacuum level above the specified value?

15 in Hg

Go Diagnostic Aids

Go to Step 15

Check for a kinked or restricted canister purge line between the EVAP canister purge valve and EVAP canister.
Repair the canister purge line as necessary

Is action complete?

0 in H2O

Go to Step 20

Ignition Switch OFF.
Remove the EVAP canister line from the fuel tank or EVAP canister. This will relieve the fuel tank pressure.
Ignition switch ON, Engine OFF.
Observe Fuel Tank Pressure on the scan tool.

Is the Fuel Tank Pressure near the specified value?

0 in H2O

Go to Step 18

Go to DTC P0453 Fuel Tank Pressure Sensor Circuit High Voltage

Important:: Do not exceed the pressure in the specified value .

Reconnect all EVAP hardware that was previously disconnected.
Ignition Switch On, Engine Off.
Using scan tool, Purge/Seal, select the seal option to seal the EVAP System.
Pressurize the system to the first specified (higher) value by slowly turning the EVAP Service station rotary switch to the Pressure position. (Monitor the pressure with the gauge on the cart with the rotary switch in the Off/Hold position).

Does the EVAP pressure decrease to less than the second specified (lower) value within 2 minutes with the rotary switch in the Off/Hold position?

15 in H2O

10 in H2O

Go to Step 3

System OK