For 1990-2009 cars

(1) | The Service Port
(2) | The Purge Valve
(3) | The Vacuum Source Pipe
(4) | The Throttle Body
(5) | The Fuel Tank Pressure Sensor
(6) | The Fuel Tank
(7) | The Fuel Filler Cap
(8) | The Vapor Pipe
(9) | The Vent Valve
(10) | The Vent Pipe
(11) | The Purge Pipe
(12) | The Vapor Canister

### Circuit Description

During specific operating conditions, the engine control module (ECM) performs various tests on the evaporative emission system. The system tests consist of the following series of events. After ensuring that the evaporative emission (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 accumulation of 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 any vapor pressure is measured, the pressure will be used later in order to compensate for a pressure reading during the small leak detection test. If a vacuum is measured which 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 reached 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 fuel tank pressure 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 fuel tank pressure sensor (DTC P0450).

### Conditions for Running the DTC

• | Any of the following DTCs are not set: P0100, P0115, P0116, P0120, P0130 thru P0161, P0300 thru P0306, P0443, P0446, P0450, P0501, P0505, P0560

• | The Vehicle Speed is 0 mph.

• | The engine is at idle

• | The ECT at start is between -8°C (17°F) and 100°C (212°F).

• | The Closed Loop is enabled.

• | The fuel tank pressure is less than 1.0 kPa (4 in. H2O).

• | The Engine Load less than 2.7 milliseconds.

• | The IAT is greater than -8°C (17°F).

• | The MAF less than 7.5 g/s

• | The System Voltage is above 11 volts

• | The Engine Run Time is at least 16 minutes 25 seconds.

• | The AIR system is inactive.

• | The AIR system diagnostic is not running.

• | The Short Term Fuel Trim at the beginning of the test is greater than -5%.

### Conditions for Setting the DTC

The diagnostic test has run to completion and determined that a failure was detected in one of the following areas:

• | Vent solenoid mechanical failure

• | Purge solenoid mechanical failure

• | Blocked or restricted lines/hoses/components

### Action Taken When the DTC Sets

The ECM illuminates the malfunction indicator lamp (MIL) and records the operating conditions in the Freeze Frame on the second consecutive drive trip that the diagnostic runs and fails.

### Conditions for Clearing the MIL/DTC

• | The ECM turns OFF the MIL after three consecutive drive trips that the diagnostic runs and passes.

• | A History DTC clears after forty consecutive warm-up cycles in which no failures are reported by this diagnostic or any other emission related diagnostic.

• | The ECM battery voltage is interrupted.

• | The scan tool clears the MIL/DTC.

### Diagnostic Aids

Check for the following conditions:

• | A damaged fuel cap

• | A damaged, pinched, or blocked EVAP purge line

• | A damaged EVAP vent hose

• | A damaged, pinched, or blocked fuel tank vapor line

• | A EVAP canister purge valve problem (non-electrical)

• | A EVAP vent solenoid problem (non-electrical)

• | A damaged EVAP canister

• | A leaking fuel sender assembly O-ring

• | A leaking fuel tank or fuel filler neck

### Test Description

The number(s) below refer to the step number(s) on the Diagnostic Table.

1. This step verifies that there is a sufficient vacuum available at the Purge valve for a proper system operation.

2. Verifies that the fuel tank vacuum sensor re-zeros to an ambient pressure.

3. Determines whether or not the EVAP system is sealed sufficiently in order to be pressurized. If not, a large leak must be located and corrected.

4. 2.69 kPa (10.8 in. H2O) is the maximum value displayable on the scan tool even though the actual pressure is higher. This step verifies that the vapor flow is not blocked somewhere between the service port and the fuel tank.

5. In the previous step, a leak was detected. This step separates the front half of the system (canister to engine) from the rear half of the system (canister to fuel tank), in order to narrow down the location of the leak.

6. Inspect the Purge valve and the vacuum lines for traces of carbon. Carbon 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 using the pressurized gas from the EVAP pressure/purge cart. Replace the Purge valve and the canister.

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

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Powertrain On-Board Diagnostic System Check? | -- | Go to Step 2 | Go to the Powertrain On Board Diagnostic (OBD) System Check
2 | Is DTC P0443 or P0446 also set? | -- | Go to the applicable DTC | Go to Step 3
3 | Before continuing with the diagnostic table, perform a visual/physical inspection of the EVAP system. Check for the following conditions:

• | Disconnected, kinked, deteriorated hoses/lines

• | Loose hose connections

• | Missing or loose fuel cap

• | Obvious damage to any of the system components

Was a problem found and corrected?

--

Go to Step 23

Go to Step 4

4 |

1. Disconnect the manifold vacuum source line at the ventilation housing hose to the purge valve, located at the rear top of the plenum.
2. Connect a vacuum gauge to the manifold vacuum source line (the in. Hg vacuum gauge on the EVAP pressure/purge cart J 41413 can be used for this purpose).
3. Start the engine.
4. Run the engine above 2000 RPM and observe source vacuum level.

Does the vacuum gauge indicate the value specified or greater?

50.79 kPa (15 in. Hg)

Go to Step 5

Go to Step 16

5 |

1. Turn off the ignition switch.
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 between the specified values?

-.249-.249 kPa (-1-1 in. H2O)

Go to Step 6

Go to DTC P0450 Fuel Tank Pressure Sensor Circuit

6 | Important: Before continuing with diagnosis, zero the EVAP Pressure and Vacuum gauges on EVAP pressure/purge cart J 41413 (refer to the tool operating instructions).

1. Connect the EVAP pressure/purge cart J 41413 to the EVAP service port.
2. Replace the fuel cap.
3. Block off the EVAP vent hose to canister using a suitable clamping tool, or disconnect the vent hose from the vent solenoid and block off the hose with a suitable stopper.
4. Attempt to pressurize the EVAP system using the pressure/purge cart. Monitor the pressure using the gauge on the cart.

Can specified value be achieved?

3.74 kPa (15 in. H2O)

Go to Step 7

Go to DTC P0455 Evaporative Emission (EVAP) System Leak Detected

7 |

1. Maintain the system pressure at the first value using the gauge on the cart.
2. Observe the Fuel Tank Pressure on the scan tool.

Is the Fuel Tank Pressure at or above the second value?

2.61 kPa (10.5 in. H2O)

1.99 kPa (8 in. H2O)

Go to Step 8

Go to DTC P0450 Fuel Tank Pressure Sensor Circuit

8 | Switch the rotary switch on the cart to HOLD and observe the EVAP pressure gauge. Does the pressure drop below the specified value within 2 minutes? | 2.49 kPa (10 in. H2O) | Go to Step 10 | Go to Step 9
9 |

1. Unblock the Vent line and/or reconnect the Vent line at the Vent Valve.
2. Disconnect the ECM.
3. Remove the Engine Controls Power Relay.
4. With a fused jumper wire, jumper the B+ circuit to the Switched B+ circuit in the relay harness connector.
5. Use another fused jumper wire in order to ground the EVAP vent valve control circuit in the ECM harness connector (closes the vent).
6. Restore the system pressure to the first specified value with the gauge on the cart.
7. Switch the rotary switch on the cart to HOLD and observe the EVAP pressure gauge.

Does the pressure drop below the second value within 2 minutes?

3.74 kPa (15 in. H2O)

2.49 kPa (10 in. H2O)

Go to Step 18

No trouble found. Refer to Diagnostic Aids

10 |

1. Disconnect the Fuel Tank Vapor line (tank to canister) at the canister and block the port on the canister using a suitable vacuum cap.
2. Restore the system pressure to the first value with the gauge on the cart.
3. Switch the rotary switch on the cart to HOLD and observe the EVAP pressure gauge.

Does the pressure drop below the second value within 2 minutes?

3.74 kPa (15 in. H2O)

2.49 kPa (10 in. H2O)

Go to Step 11

Go to Step 14

11 |

1. Disconnect the Purge line (valve to canister) at the Purge Valve and block the line using a suitable stopper.
2. Restore the system pressure to the first value using the gauge on the cart.
3. Switch the rotary switch on the cart to HOLD and observe EVAP pressure gauge.

Does the pressure drop below the second value within 2 minutes?

3.74 kPa (15 in. H2O)

2.49 kPa (10 in. H2O)

Go to Step 12

Go to Step 17

12 |

1. Disconnect the Vent line at the canister and block the port on the canister using a suitable vacuum cap.
2. Restore the system pressure to the first specified value with the gauge on the cart.
3. Switch the rotary switch on the cart to HOLD and observe EVAP pressure gauge.

Does the pressure drop below the second value within 2 minutes?

3.74 kPa (15 in. H2O)

2.49 kPa (10 in. H2O)

Go to Step 13

Go to Step 20

13 |

1. Disconnect the Purge line at the canister and block the line with a suitable stopper.
2. Restore the system pressure to the first specified value with the gauge on the cart.
3. Switch the rotary switch on the cart to HOLD and observe the EVAP pressure gauge.

Does the pressure drop below the second value within 2 minutes?

3.74 kPa (15 in. H2O)

2.49 kPa (10 in. H2O)

Go to Step 21

Go to Step 19

14 |

1. Reconnect the Fuel Tank Vapor line (tank to canister) at the canister.
2. Disconnect the Fuel Tank Vapor line at the fuel tank and block the line with a suitable stopper.
3. Restore the system pressure to the first specified value with the gauge on the cart.
4. Switch the rotary switch on the cart to HOLD and observe the EVAP pressure gauge.

Does the pressure drop below the second value within 2 minutes?

3.74 kPa (15 in. H2O)

2.49 kPa (10 in. H2O)

Go to Step 22

Go to Step 15

15 |

1. Reconnect the Fuel Tank Vapor line (tank to canister) at the tank.
2. With the cart connected to the EVAP service port continuously attempt to pressurize the EVAP system by leaving the cart, control the knob in the pressurize position.
3. Check the fuel tank for leaks with the ultrasonic leak detector J 41416. Check the following areas and repair as necessary:

• | The fuel tank and the tank seams

• | The filler cap/fill pipe area

• | The sending unit and the sending unit to tank seal

• | The Fuel Tank Pressure sensor

Is the action complete?

--

Go to Step 23

--

16 | Check for the following conditions and repair as necessary:

• | A damaged vacuum source line

• | A blocked or restricted manifold vacuum port

• | A low engine vacuum.

Is the action complete?

--

Go to Step 23

--

17 | Important: Contamination can cause the valve to fail. Refer to Test Description for inspection/cleaning procedures. Replace the purge valve. Is the action complete? | -- | Go to Step 23 | --
18 | Replace the Vent valve. Is the action complete? | -- | Go to Step 23 | --
19 | Replace the canister. Is the action complete? | -- | Go to Step 23 | --
20 | Replace the vent line. Is the action complete? | -- | Go to Step 23 | --
21 | Replace the purge line (valve to canister). Is the action complete? | -- | Go to Step 23 | --
22 | Replace the vapor line (tank to canister). Is the action complete? | -- | Go to Step 23 | --
23 |

1. Disconnect the ECM.
2. Remove the Engine Controls Power Relay.
3. With a fused jumper wire, jumper the B+ circuit to the Switched B+ circuit in the relay harness connector.
4. Use another fused jumper wire in order to ground the EVAP vent valve control circuit in the ECM harness connector (closes the vent).
5. Pressurize the EVAP system to the first value with the EVAP pressure/purge cart J 41413. (Monitor the pressure with the gauge on the cart).
6. Switch the rotary switch on the cart to HOLD and observe the pressure gauge.

Does the pressure drop below the second value within 2 minutes?

3.74 kPa (15 in. H2O)

2.49 kPa (10 in. H2O)

Go to Step 6

Go to Step 24

24 |

1. Clear the DTCs with the scan tool.
2. Turn off the ignition for 15 seconds.
3. Operate the vehicle with the conditions that are required for this vehicle to run. Refer to Conditions for Running the DTC.
4. Check for any DTCs.

Is this DTC set?

--

Go to Step 5

Go to Step 25

25 | Were there any additional DTCs noted during the Powertrain OBD System Check that have not been diagnosed? | -- | Go to the applicable DTC table | The System is OK