For 1990-2009 cars

### Circuit Description

The DTC P0455 Evaporative Emission (EVAP) System Leak Detected diagnostic monitors the operation of the EVAP system. The evaporative emission (EVAP) control system leak detection diagnostic strategy is based on applying vacuum to the EVAP system and monitoring vacuum decay. The powertrain control module (PCM) monitors the vacuum level via the fuel tank pressure sensor input. The PCM turns ON the EVAP canister purge valve and the EVAP vent valve, allowing the engine manifold pressure to draw a small vacuum on the entire EVAP system. If sufficient vacuum cannot be sustained over a given period of time, a small leak or a malfunction is suspected and DTC P0455 sets. The EVAP system used with this powertrain is part of an on-board refueling vapor recovery (ORVR) fuel system.

The EVAP system as defined by federal regulation includes the following components:

• | The fuel tank

• | The EVAP canister vent valve

• | The fuel tank pressure (FTP) sensor

• | The fuel pipes and hoses

• | The vapor lines

• | The fuel filler cap

• | The fuel tank pressure control valve

• | The EVAP canister

• | The purge lines

• | The EVAP canister purge valve

### Condition for Running the DTC

• | The engine coolant temperature is between 70-110°C (158°F-230°F)

• | The intake air temperature is between -7°C to +70°C (19°F-158°F).

• | The barometric pressure (BARO) is more than 75 kPa.

• | The fuel tank level is less than 75 percent.

• | The engine is operating in Closed Loop.

• | The engine speed is between 1,000-3,000 RPM (A/T), or 1,000-3,500 RPM (M/T).

### Conditions for Setting the DTC

The difference between the maximum internal pressure of the fuel tank and the minimum pressure is less than a specified value.

The diagnostic may take up to 20 minutes to run.

### Action Taken When the DTC Sets

• | The PCM illuminates the malfunction indicator lamp (MIL) after 2 consecutive ignition cycles in which the diagnostic runs with the fault active.

• | The PCM records the operating conditions at the time the diagnostic fails. This information is stored in the Freeze Frame buffer.

### Conditions for Clearing the MIL/DTC

• | MIL turns OFF after 3 consecutively passing trips without a fault present.

• | History DTC clears after 40 consecutive warm-up cycles without a fault.

• | Perform the scan tool Clear DTC Information function in order to clear the DTC.

### Diagnostic Aids

If a DTC P0455 is intermittent, driving the vehicle under the conditions outlined in the Inspection/Maintenance (I/M) section can verify whether the fault is present. Refer to Inspection/Maintenance Evaporative Emission System Set .

A faulty or erratic fuel level sensor can cause DTC P0455 to set. Use the scan tool in order to check the operation of the fuel level sensor. If the accuracy of the fuel level sensor is suspect, refer to DTC P0461 .

The EVAP purge diagnostic checks for many of the faults that can cause DTC P0455 to set. If the EVAP Purge test passes the cause of the DTC P0455 is probably intermittent. Clear the DTCs. Road test the vehicle while monitoring the EVAP Purge in the MIL/System Status selection under System Information on the scan tool. When the EVAP Purge indicates complete with a YES status, check for DTC P0455 under Last Test Failed. If there is no DTC P0455 indicated, the DTC is intermittent and the purge system diagnostic is indicating OK at this time.

For functional checks of the components listed above, refer to Evaporative Emission Control System Diagnosis .

An intermittent malfunction may be caused by a fault in any of the EVAP control system electrical circuits. Inspect the wiring harness and components for an intermittent condition. Refer to Intermittent Conditions .

If the DTC P0455 cannot be duplicated, the information included in the Freeze Frame data can be useful in determining vehicle operating conditions when the DTC was first set.

### Test Description

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

1. The Diagnostic System Check-Engine Controls prompts the technician to complete some basic checks and store the Freeze Frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.

2. This step checks the operation of the FTP sensor. If the FTP sensor does not indicate near zero pressure when the fuel filler cap is removed, the FTP sensor or circuit might be faulty. The FTP sensor can be checked by using the diagnostics in DTC P0450.

3. This step uses tools from the EVAP pressure/purge cart diagnostic station, in order to determine whether EVAP control system is sealed sufficiently to be pressurized. Any leak that is found must be located and repaired before continuing with the diagnosis.

4. This step checks the components that supply manifold vacuum to the EVAP canister purge valve.

5. This step checks the operation of the EVAP canister purge valve. The duty cycle control of the EVAP canister purge valve is disabled by the PCM when any DTCs are stored and when engine speed is indicated.

6. This step checks the operation of the EVAP canister vent valve. The output control of the EVAP canister vent valve is disabled by the PCM when any DTCs are stored and when engine speed is indicated.

7. This step checks the control circuit of the EVAP canister vent valve. The output control of the EVAP canister vent valve is disabled by the PCM when any DTCs are stored and when engine speed is indicated.

8. This step determines whether or not the malfunction that caused DTC P0455 is still present. Driving the vehicle under these conditions will verify whether the fault is present. After performing the scan tool Clear DTC Information function, the DTC P0455 diagnostic can be monitored on the scan tool under the Not Ran Since Code Cleared selection in the DTC Information menu. If DTC P0455 appears in the Not Ran Since Code Cleared list, the DTC P0455 diagnostic has not yet run. When DTC P0455 does not appear in the Not Ran Since Code Cleared list, the DTC P0455 diagnostic has run. If the MIL is NOT illuminated and there is no Pending DTC Status in DTC Information, the DTC P0455 diagnostic has passed. The DTCs MUST be cleared in order to view the Current Status of the Not Ran Since Code Cleared list. The DTC Information screen must be checked for Current or Pending status in order to determine the outcome of the diagnostic test involved.

Step | Action | Value(s) | 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 | Are any EVAP codes set other than a DTC P0440 or a DTC P0455? | -- | Go to Diagnostic Trouble Code (DTC) List | Go to Step 3
3 |

1. Observe the fuel tank pressure (FTP) Sensor parameter with a scan tool.
2. Remove the fuel filler cap.

Is the fuel tank pressure within the specified range with the fuel filler cap removed?

0.0-0.9 mm Hg (0.0-0.5 in. H2O)

Go to Step 4

Go to DTC P0450

4 | Visually inspect the entire EVAP control system for any of the following conditions:

• | Loose or incorrect fuel filler gas cap

• | Loose hose connections

• | Damaged or deteriorated hoses

• | Clogged or restricted lines and hoses

• | Missing or damaged components

Was a problem found?

--

Go to Step 7

Go to Step 5

5 |

1. Turn ON the ignition, leaving the engine OFF.
2. Remove the fuel cap and install the gas cap adapter.
3. Connect the J 41413 EVAP Pressure/Purge Diagnostic Station to the gas cap adapter.
4. Command the EVAP canister vent valve ON with the scan tool.
5. Pressurize the EVAP system to the first specified value using the J 41413 . Monitor the pressure using the gauge on the cart.
6. Turn the rotary switch on the J 41413 to the HOLD position and observe the EVAP pressure gauge.

Does the pressure decrease to less than the second specified value within 2 minutes?

28 mm Hg (15 in. H2O)

18.6 mm Hg (10 in. H2O)

Go to Step 6

Go to Step 8

6 |

1. With the Step 14 conditions met, continually attempt to pressurize the EVAP system to the specified value.
2. Locate any leaks in the EVAP system using the J 41416 Ultrasonic Leak Detector. In order to examine the top tank connections, partially lower the fuel tank.

Were any leaks found?

56 mm Hg (30 in. H2O)

Go to Step 7

Go to Step 8

7 | Repair or replace any leaking or faulty EVAP control system components. Is the action complete? | -- | Go to Step 30 | --
8 |

1. Check for any of the following conditions at the EVAP canister purge valve:

• | No manifold vacuum from the intake manifold vacuum port

• | Leaking or damaged vacuum hoses

• | Restricted vacuum hoses or passages

2. Repair any condition found during the above checks.

Was a repair necessary?

--

Go to Step 30

Go to Step 9

9 | Caution: Do not breathe the air through the EVAP component tubes or hoses. The fuel vapors inside the EVAP components may cause personal injury.

1. Turn ON the ignition, leaving the engine OFF.
2. Disconnect the vacuum hoses to the EVAP canister purge valve from the intake manifold and from the EVAP canister.
3. Blow air into the vacuum hose that was disconnected from the EVAP canister. Air should not pass through the EVAP canister purge valve and exit from the intake manifold hose.
4. Command the EVAP canister purge valve ON and adjust the duty cycle to 100 percent with the scan tool.
5. Blow air into the vacuum hose that was disconnected from the EVAP canister. Air should pass through the EVAP canister purge valve and exit from the intake manifold hose.

Does the EVAP canister purge valve pass both inspections?

--

Go to Step 12

Go to Step 10

10 |

1. Turn ON the ignition, leaving the engine OFF.
2. Probe the ignition positive voltage circuit at the electrical connector terminal 1 of the EVAP canister purge valve with a test lamp connected to ground.

Does the test lamp illuminate?

--

Go to Step 11

Go to Step 20

11 |

1. Probe the control circuit for the EVAP canister purge valve at the electrical connector with a test lamp connected to B+.
2. Command the EVAP canister purge valve ON with the scan tool. Adjust the duty cycle from 0-100 percent while monitoring the test lamp.

Does the test lamp flash and then illuminate fully as the duty cycle reaches 100 percent?

--

Go to Step 28

Go to Step 27

12 | Caution: Do not breathe the air through the EVAP component tubes or hoses. The fuel vapors inside the EVAP components may cause personal injury.

1. Turn OFF the ignition.
2. Remove the EVAP canister vent valve. Refer to Evaporative Emission Canister Vent Solenoid Valve Replacement .
3. Blow air into the EVAP canister vent valve port, located on the side that was connected to the EVAP canister air filter.

Did the air pass thorough to the other side of the EVAP canister vent valve?

--

Go to Step 13

Go to Step 25

13 |

1. Turn ON the ignition, leaving the engine OFF.
2. Command the EVAP canister vent valve ON using a scan tool.
3. Blow air into the EVAP canister vent valve port, located on the side that was connected to the EVAP canister air filter.

Was the air unable to pass thorough the EVAP canister vent valve?

--

Go to Step 14

Go to Step 15

14 |

1. Continue to blow air into the EVAP canister vent valve.
2. Command the EVAP canister vent valve OFF with the scan tool.

Did the air pass thorough the EVAP canister vent valve when the scan tool commanded the vet valve OFF?

--

Go to Step 17

Go to Step 21

15 |

1. Turn OFF the ignition.
2. Disconnect the electrical connector from the EVAP canister vent valve .
3. Turn ON the ignition, leaving the engine OFF.
4. Probe the harness side of terminal 1 of the EVAP canister vent valve with a test lamp connected to ground.

Does the test lamp illuminate?

--

Go to Step 16

Go to Step 20

16 |

1. Command the EVAP canister vent valve ON with the scan tool.
2. Probe the harness side of terminal 2 of the EVAP canister vent valve with a test lamp connected to B+.

Does the test lamp illuminate?

--

Go to Step 25

Go to Step 23

17 |

1. Disconnect the vacuum/vapor hoses from the EVAP canister.
2. Blow air into the tank port of the EVAP canister. There should be no restriction of air flow thorough the canister and out the purge pipe and the air port. Refer to Evaporative Emission Control System Diagnosis .

Did the EVAP canister pass the test?

--

Go to Step 18

Go to Step 22

18 | Caution: Do not breathe the air through the EVAP component tubes or hoses. The fuel vapors inside the EVAP components may cause personal injury.

1. Remove the fuel tank pressure (FTP) control valve. Refer to Fuel Tank Pressure Control Valve Replacement .
2. Connect a vacuum hose to the canister side port of the FTP control valve.

Important: There will be some resistance, but air should flow steadily.

3. Blow air into the hose on the FTP control valve.

Did the air flow through the valve to the tank port side?

--

Go to Step 19

Go to Step 26

19 | Important: The FTP control valve allows vapor to flow from the fuel tank to the canister when the fuel tank pressure is greater than canister pressure by more than 3.5 kPa (0.5 psi).

1. Move the vacuum hose to the fuel tank port of the FTP control valve.
2. Blow hard into the hose connected to the tank port side of the FTP control valve. Air should flow easily through the valve and out of the canister port.

Did the FTP control valve pass this test?

--

Go to Step 24

Go to Step 26

20 | Repair the open in the ignition positive voltage circuit between terminal 1 and the main relay. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 30 | --
21 |

1. Check for a short to ground in the control circuit between the EVAP canister vent valve and the PCM.
2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 30

Go to Step 29

22 | Replace the EVAP canister. Refer to Evaporative Emission Canister Replacement . Is the action complete? | -- | Go to Step 30 | --
23 |

1. Check for an open in the control circuit of the EVAP canister vent valve .
2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 30

Go to Step 29

24 |

1. Inspect the EVAP canister air filter and hoses for restrictions or blockage.
2. Repair as necessary. Refer to Evaporative Emission Canister Filter Replacement .

Was a repair necessary?

--

Go to Step 30

Go to Diagnostic Aids

25 | Replace the EVAP canister vent valve. Refer to Evaporative Emission Canister Vent Solenoid Valve Replacement . Is the action complete? | -- | Go to Step 30 | --
26 | Replace the FTP control valve. Refer to Fuel Tank Pressure Control Valve Replacement . Is the action complete? | -- | Go to Step 30 | --
27 |

1. Check for an open or a short in the control circuit of the EVAP canister purge valve .
2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 30

Go to Step 29

28 | Replace the EVAP canister purge valve. Refer to Evaporative Emission Canister Purge Solenoid Valve Replacement . Is the action complete? | -- | Go to Step 30 | --
29 | Important: The replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement . Is the action complete? | -- | Go to Step 30 | --
30 |

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 vehicle within the Freeze Frame conditions that set the DTC or until the P0455 diagnostic test has run. Refer to the test description.

Does the DTC run and pass?

--

Go to Step 31

Go to Step 2

31 | 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