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.
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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.
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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.
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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.
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This step checks the components that supply manifold vacuum to the EVAP canister purge valve.
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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.
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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.
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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.
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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 | ||||||||||||||
Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | ||||||||||||
2 | Are any EVAP codes set other than a DTC P0440 or a DTC P0455? | -- | Go to Step 3 | |||||||||||
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:
Was a problem found? | -- | Go to Step 7 | Go to Step 5 | ||||||||||
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 |
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 | -- | ||||||||||
Was a repair necessary? | -- | Go to Step 30 | Go to Step 9 | |||||||||||
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Caution: Do not breathe the air through the EVAP component tubes or hoses. The fuel vapors inside the EVAP components may cause personal injury.
Does the EVAP canister purge valve pass both inspections? | -- | Go to Step 12 | Go to Step 10 | |||||||||||
10 |
Does the test lamp illuminate? | -- | Go to Step 11 | Go to Step 20 | ||||||||||
11 |
Does the test lamp flash and then illuminate fully as the duty cycle reaches 100 percent? | -- | Go to Step 28 | Go to Step 27 | ||||||||||
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Caution: Do not breathe the air through the EVAP component tubes or hoses. The fuel vapors inside the EVAP components may cause personal injury.
Did the air pass thorough to the other side of the EVAP canister vent valve? | -- | Go to Step 13 | Go to Step 25 | |||||||||||
13 |
Was the air unable to pass thorough the EVAP canister vent valve? | -- | Go to Step 14 | Go to Step 15 | ||||||||||
14 |
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 |
Does the test lamp illuminate? | -- | Go to Step 16 | Go to Step 20 | ||||||||||
Does the test lamp illuminate? | -- | Go to Step 25 | Go to Step 23 | |||||||||||
17 |
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.
Important: There will be some resistance, but air should flow steadily. 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).
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 |
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 |
Was a repair necessary? | -- | Go to Step 30 | Go to Step 29 | ||||||||||
24 |
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 |
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 | -- | ||||||||||
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? | -- | System OK | |||||||||||
