For 1990-2009 cars

### Circuit Description

During specific operating conditions, the engine control module (ECM) performs various tests on the evaporative emission (EVAP) system. These tests consist of the following series of events: After ensuring that the EVAP purge solenoid valve duty cycle has dropped to 0 percent, indicating that the valve is closed, the ECM commands the EVAP canister vent solenoid valve closed, sealing the system. The ECM monitors the vapor pressure within the fuel tank via the fuel tank pressure (FTP) sensor. The EVAP test is aborted if the vapor pressure is too high. If a vacuum is measured that exceeds a calculated limit during vapor accumulation, diagnostic trouble code (DTC) P0440 will set. The EVAP canister purge solenoid valve is then opened. Simultaneously, the vent solenoid is opened. If the vapor pressure does not bleed off or bleeds off too slowly, DTC P0440 is set. Once the EVAP purge solenoid valve reaches the desired position for the remainder of the diagnostic test, the vent solenoid will be closed again. This causes a vacuum to be applied to the entire EVAP system. The ECM monitors the vacuum level within the system. If the desired vacuum level cannot be achieved, or if the vacuum level is reached but took too much time, DTC P0455 will set. Once the desired vacuum level is reached, the purge solenoid is closed, sealing the system. The ECM continues to monitor the FTP sensor signal, measuring the rate of vacuum decay. If the system holds vacuum, the vent solenoid is opened and the test is completed. In addition to the system tests, the ECM monitors the circuit integrity of the purge solenoid, DTC P0443, the vent solenoid DTC P0446, and the FTP sensor DTC P0450.

### Conditions for Running the DTC

• | DTCs P0100, P0115, P0116, P0130-P0161, P0300-P0306, P0443, P0446, P0450, P0500, P0506, P0507, P0560, P1120, or P1220 are not set.

• | The vehicle speed is 0 km/h (0 mph).

• | The engine is at idle.

• | The engine coolant temperature (ECT) at start is between -8 to +75°C (+17-167°F).

• | Fuel system is in Closed Loop.

• | The engine load is less than 30 percent.

• | The intake air temperature (IAT) is between -8 to +50°C (+17-122°F).

• | The system voltage is more than 11 volts.

• | The engine run time is at least 17 minutes.

• | The secondary air injection (AIR) system is inactive.

• | The secondary AIR system diagnostic is not running.

• | The short term fuel trim at the beginning of the test is more than -5 percent.

### Conditions for Setting the DTC

The fuel tank pressure is less than -6 mm Hg (-3.2 in. H2O) while opening the purge solenoid.

OR

The EVAP vapor pressure does not bleed off or bleeds off too slowly when the vent solenoid is commanded open.

OR

The fuel tank pressure is less than -10.5 mm Hg (-5.6 in. H2O) for 15 seconds.

### 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 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

Check for the following conditions:

• | Incorrectly routed EVAP system lines

• | A damaged fuel cap

• | A damaged, pinched, or blocked EVAP vent hose

• | An EVAP canister purge valve stuck open

• | An EVAP vent solenoid stuck closed or opening too slowly

• | Inspect the purge line and valve for traces of carbon. Any carbon escaping from the canister may prevent the valve from closing properly. If traces of carbon are found, disconnect both ends of the purge line and blow out any contaminants by using the pressurized gas from the EVAP pressure/purge cart. Replace the purge valve and the canister and fuel tank.

### Test Description

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

1. This step is to determine if the fuel pressure sensor is skewed.

2. This step is to determine if the purge valve is not sealed when commanded closed.

3. Inspect the purge valve and lines for traces of carbon. Any carbon that is escaping from the canister may be preventing the valve from closing properly. If this condition is found, disconnect both ends of the purge line and blow out any contaminants by using the pressurized gas from the EVAP pressure/purge cart. Replace the purge valve and the canister/fuel tank.

#### DTC P0440 - Evaporative Emission (EVAP) System

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
Schematic Reference: 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 | Is DTC P0443, P0446, or P0450 also set? | -- | Go to Diagnostic Trouble Code (DTC) List | Go to Step 3
3 | Perform a visual and physical inspection of the EVAP system before continuing with the diagnostic table. Check for the following conditions and correct as necessary:

• | Disconnected, kinked, or deteriorated hoses/lines

• | Fuel filler neck switch valve stuck

• | Obvious damage to any of the system components

Did you find and correct the condition?

--

Go to Step 14

Go to Step 4

4 |

1. Turn OFF the ignition.
2. Remove the fuel cap.
3. Turn ON the ignition, with the engine OFF.
4. Observe the fuel tank pressure on the scan tool.

Is the fuel tank pressure within the specified range?

-1.87 to +1.87 mm Hg

(-1 to +1 in. H2O)

Go to Step 5

Go to DTC P0450

5 |

1. Disconnect the purge line from the EVAP service port.
2. Connect a vacuum gauge to the purge line from the purge valve. The in. H2O vacuum gauge on the J 41750 EVAP Pressure/Purge Cart can be used for this purpose.
3. Start the engine and allow it to idle.
4. Using the scan tool, command the purge valve to 0 percent.
5. Observe the vacuum gauge.

Does the vacuum gauge indicate any vacuum?

--

Go to Step 13

Go to Step 6

6 | Important: Before continuing with diagnosis, zero the EVAP pressure and vacuum gauges on the J 41750 . Refer to the tool operating instructions.

1. Turn OFF the ignition.
2. Reconnect the purge line to the EVAP service port.
3. Replace the fuel cap.
4. Connect the EVAP pressure/purge cart to the EVAP service port.
5. Turn ON the ignition.
6. Use the scan tool to command the vent valve ON, closed.
7. Pressurize the EVAP system to the specified value using the pressure/purge cart.
8. Rotate the valve on the cart to HOLD.
9. Command the vent valve OFF, open.
10. Observe the gauge on the cart as the vent valve is opened.

Does the system pressure release immediately as the vent valve opens?

28.02 mm Hg (15 in. H2O)

Go to Diagnostic Aids

Go to Step 7

7 |

1. Verify the system pressure is at the specified value and adjust if necessary.
2. Remove the vent valve inlet hose from the vent valve while monitoring the gauge.

Does the system pressure release immediately as the vent inlet hose is removed?

28.02 mm Hg (15 in. H2O)

Go to Step 9

Go to Step 8

8 |

1. Reconnect the vent valve inlet hose.
2. Verify the system pressure is at the specified value and adjust if necessary.
3. Remove the vent hose from the fuel tank at the vent valve while monitoring the gauge on the cart.

Does the system pressure release immediately as the vent hose is removed?

28.02 mm Hg (15 in. H2O)

Go to Step 12

Go to Step 10

9 | Inspect the vent valve inlet hose for a restriction. Repair or replace as necessary. Did you find and correct the condition? | -- | Go to Step 14 | --
10 | Inspect the vent hose to the fuel tank for a restriction. Repair or replace as necessary. Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 11
11 | Replace the EVAP canister and fuel tank. Refer to Fuel Tank and Evaporation Emission Canister Replacement . Did you complete the replacement? | -- | Go to Step 14 | --
12 | Replace the vent valve. Refer to Evaporative Emission Canister Vent Solenoid Valve Replacement . Did you complete the replacement? | -- | Go to Step 14 | --
13 | Replace the purge valve. Refer to Evaporative Emission Canister Purge Solenoid Valve Replacement . Did you complete the replacement? | -- | Go to Step 14 | --
14 |

1. Use the scan tool in order to clear the DTCs.
2. Turn OFF the ignition for 30 seconds.
3. Start the engine.
4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC run and pass?

--

Go to Step 15

Go to Step 2

15 | 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