Circuit Description
The DTC P0440 Evaporative Emission (EVAP) System diagnostic monitors the fuel tank side of the EVAP canister for leaks and correct operation. The powertrain control module (PCM) monitors the positive or negative pressure in the fuel tank, using the fuel tank pressure (FTP) sensor. Under certain engine operating conditions, the PCM turns ON the EVAP pressure switching solenoid in order to control the pressure in the EVAP system. The PCM is able to detect any abnormal conditions by the fluctuation of this pressure. The diagnostics performed by the fuel tank pressure sensor can warn the driver of a malfunction in the EVAP system by illuminating the malfunction indicator lamp (MIL). The EVAP control system prevents the emission of the fuel vapors. The fuel vapor generated in the fuel tank while driving or idling enters the EVAP canister where a charcoal element absorbs and stores the fuel vapor. The EVAP canister is purged by the PCM controlled EVAP canister purge valve. The EVAP canister purge valve releases the fuel vapors into the intake manifold to be burned in the combustion process.
Conditions for Running the DTC
| • | The barometric pressure (BARO) is more than 75 kPa. |
| • | The fuel level is between ¼ and ¾. |
| • | The engine coolant temperature (ECT) sensor is between 10-35°C (50-95°F) at engine start. |
| • | The ECT sensor and the intake air temperature (IAT) sensor are near the same temperature at engine start. |
| • | The ECT sensor is at least 70°C (158°F) after engine warm up. |
| • | The vehicle has been driven for at least 20 minutes. |
| • | The EVAP canister purge valve has been open and the fuel tank pressure (FTP) sensor indicates a negative pressure in the fuel tank. |
Conditions for Setting the DTC
The FTP sensor indicates a change in pressure when the EVAP canister purge valve and EVAP canister vent valve are both closed.
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
| • | The PCM turns OFF the MIL on the third consecutive trip cycle during which the diagnostic has been run and the fault condition is no longer present. |
| • | A DTC will clear after 40 consecutive warm-up cycles have occurred without a fault. |
| • | A DTC can be cleared by using the scan tool Clear Information function. |
Diagnostic Aids
| • | If DTCs P0441, P0446, or P0450 is set, diagnose those DTCs first. |
| • | A DTC P0440 is more likely to set during city driving. Avoid operating the vehicle on the highway when validating DTC P0440. |
| • | If a DTC P0440 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 . |
| • | The DTC P0440 diagnostic checks for EVAP system leaks on the fuel tank side of the EVAP system. A fault in the fuel tank pressure (FTP) sensor or a leak in any of the fuel tank components can cause DTC P0440 to set. Check for any of the following conditions: |
| - | A faulty FTP sensor |
| - | A loose or faulty fuel tank filler cap |
| - | A factory correct fuel tank filler cap that meets OEM specifications |
| - | A faulty or leaking fill limiter vent valve |
| - | A leak in the fuel tank |
| - | A faulty or leaking EVAP canister |
| - | Any incorrectly routed or installed EVAP system lines and hoses |
| - | Any damaged or leaky hoses, lines, or fittings between the fuel tank, the FTP sensor, and the EVAP canister |
| • | 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 the FTP sensor electrical circuit. Inspect the wiring harness and components for an intermittent condition. Refer to Intermittent Conditions . |
If DTC P0440 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 for a possible leak in the EVAP system. The purpose of this inspection is to determine whether 5-6 inches of H2O can be obtained and held for at least 2 minutes.
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This step determines if a FTP sensor malfunction is present. The input signal of the fuel tank pressure sensor should indicate atmospheric pressure with the fuel tank filler cap removed. The fuel tank pressure sensor will vary with atmospheric pressure. A typical pressure at sea level is between 0.0-0.99 mm Hg (0.0-0.5 in H2O).
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This step checks for conditions that can cause the fuel vapor pressure to remain trapped at the fuel tank pressure sensor.
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This step determines if the malfunction that caused the DTC P0440 is still present. Operating the vehicle in check mode enhances PCM diagnostic capabilities. The EVAP diagnostic can be monitored on the scan tool under the I/M System Information. When the EVAP test displays a YES status, indicating that the EVAP system diagnostic is completed, check for a DTC P0440 in the Last Test Failed screen of the scan tool. If there is no DTC P0440 displayed the EVAP system diagnostic has run and passed, indicating that no malfunction was present this time. DTCs MUST be cleared in order to view the Current Status of the system diagnostics being performed. Do not forget that the I/M System Information tests only indicate that the test has run, not whether the test passed or failed. The Last Test Failed screen must be checked for related DTCs in order to determine the outcome of the diagnostic test involved.
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This step checks for leaks in the fuel supply system. By plugging the ORVR vent line and the EVAP vapor line, the fuel tank side of the EVAP system can be pressurized and checked for leaks. Be sure to check all connections and sealing points for leaks.
Step | Action | Values | Yes | No | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||||||||||||
Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | ||||||||||||
2 |
Is a DTC P0450 or P0451 present? | -- | Go to Step 3 | |||||||||||
3 | Is a DTC P0441 or a DTC P0446 set along with a DTC P0440? | -- | Go to Step 4 | |||||||||||
4 |
Was repair necessary? | -- | Go to Step 21 | Go to Step 5 | ||||||||||
Does the EVAP system hold the specified pressure for at least 2 minutes? | 8.5-10.5 mm Hg (4.5-5.5 in H2O) | Go to Step 6 | Go to Step 16 | |||||||||||
Is the FTP sensor within the specified range? | 0.0-0.99 mm Hg (0.0-0.5 in H2O) | Go to Step 15 | Go to Step 7 | |||||||||||
7 |
Is the FTP sensor within the specified range? | 0.0-0.99 mm Hg (0.0-0.5 in H2O) | Go to Step 8 | Go to Step 9 | ||||||||||
Is the action complete? | -- | Go to Step 21 | -- | |||||||||||
9 |
Does the voltage equal the specified value? | 5.0 V | Go to Step 10 | Go to Step 11 | ||||||||||
10 | Measure the voltage from the FTP sensor connector cavity 2 on the harness side with a DMM. Is the voltage near the specified value? | 4.9 V | Go to Step 13 | Go to Step 12 | ||||||||||
11 | Repair the open in the reference voltage circuit of the FTP sensor between the sensor and SP259. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 21 | -- | ||||||||||
12 |
Was a repair necessary? | -- | Go to Step 21 | Go to Step 20 | ||||||||||
13 | Probe the FTP sensor connector cavity 1 on the harness side with a test lamp connected to battery voltage. Does the test lamp illuminate? | -- | Go to Step 19 | Go to Step 14 | ||||||||||
14 | Repair the open in the ground circuit of the FTP sensor between the sensor and S206. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 21 | -- | ||||||||||
Did DTC P0440 set? | -- | Go to Step 17 | Fault Not Present-Go to Diagnostic Aids | |||||||||||
Refer to the Evaporative Emission Control System Description for the EVAP system hose routing diagram used in the following procedure.
Were any EVAP or fuel supply system leaks found? | 29 mm Hg (15 in H2O) | Go to Step 18 | Go to Step 17 | |||||||||||
17 | Replace the EVAP canister. Refer to Evaporative Emission Canister Replacement . Is the action complete? | -- | Go to Step 21 | -- | ||||||||||
18 | Repair or replace the leaking EVAP system or fuel tank component. Is the action complete? | -- | Go to Step 21 | -- | ||||||||||
19 | Replace the FTP sensor. Refer to Fuel Tank Pressure Sensor Replacement . Is the action complete? | -- | Go to Step 21 | -- | ||||||||||
20 | Replace the PCM. Refer to Powertrain Control Module Replacement . Is the action complete? | -- | Go to Step 21 | -- | ||||||||||
21 |
Does the DTC run and pass? | -- | Go to Step 22 | Go to Step 2 | ||||||||||
22 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |||||||||||
