The PCM monitors the positive or negative pressure in the fuel tank using the fuel tank pressure sensor. Under certain engine operating conditions, the PCM turns ON the EVAP pressure switching solenoid in order to monitor the positive or negative pressure in different sides of 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 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 (cleaned) by the PCM controlled EVAP canister purge solenoid valve. The EVAP canister purge solenoid valve releases the fuel vapors into the intake manifold to be burned in the combustion process.
• | Engine coolant temperature is greater than 70°C (158°F). |
• | The vehicle has been driven for at least 20 minutes. |
• | Fuel tank level is between 25 and 75%. |
The fuel tank pressure sensor indicates atmospheric pressure in the fuel tank.
• | The PCM illuminates the malfunction indicator lamp (MIL) after two 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. |
• | 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. |
If a DTC P0441, P0446, or P0450 is set, daignose those DTCs first.
A DTC P0440 is more likely to set during city driving. Avoid operating the vehicle on the highway when validating a DTC P0440.
The DTC P0440 daignostic checks for EVAP system leaks on the fuel tank side of the EVAP system. A fault in the fuel tank pressure sensor or a leak in any of the fuel tank components can cause a DTC P0440 to set. Check for any of the following conditions:
• | A faulty fuel tank pressure sensor |
• | A loose or faulty fuel tank filler cap |
• | A factory correct fuel tank filler cap |
• | A faulty or leaking fill limiter vent valve (FLVV) |
• | A leak in the fuel tank |
• | A faulty or leaking EVAP canister |
• | Damaged or leaky hoses, lines, or fittings between the fuel tank, the fuel tank presssure 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 fuel tank pressure sensor electrical circuit. Inspect the wiring harness and components for any of the following conditions:
• | Backed out terminals. |
• | Improper mating of terminals. |
• | Broken electrical connectors locks. |
• | Improperly formed or damaged terminals |
• | Faulty terminal to wire connections. |
• | Physical damage to the wiring harness. |
• | A broken wire inside the insulation. |
• | Corrosion of electrical connections, splices, or terminals. |
Repair any electrical circuit faults that were found. Refer to Wiring Repairs in Wiring Systems.
If the 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.
The numbers below refer to the step numbers in the Diagnostic Table.
The OBD System Check 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.
This step checks for a possible leak in the EVAP system from the fuel tank to the fuel tank pressure sensor. Normal operation of the EVAP canister prevents EVAP system pressure from exceeding 3.3 mm Hg (6.0 in H2O). The purpose of this inspection is to determine whether 5 to 6 inches of H2O can be obtained and held for at least 2 minutes.
This step checks whether a fuel tank pressure sensor malfunction is present. The input signal voltage of the fuel tank pressure sensor should indicate atmospheric pressure, 3.0 to 3.6 volts, with the fuel tank filler cap removed. The fuel tank pressure sensor voltage will vary with atmospheric pressure. A typical voltage at sea level is 3.2-3.3 volts.
When the EVAP pressure switching solenoid turns ON, fuel tank vapor pressure is applied to the fuel tank pressure sensor thru the EVAP canister. Turning ON the EVAP pressure switching solenoid while pressurizing the fuel tank should cause the fuel tank pressure sensor voltage to increase.
This step checks for a condition that causes fuel vapor pressure to remain trapped at the fuel tank pressure sensor.
This step checks whether the malfunction that caused the DTC P0440 is still present. Operating the vehicle in check mode enhances the PCM's diagnostic capabilities. The EVAP Purge diagnostic can be monitored on the scan tool under the MIL/System Status selection of System Information. When the EVAP Purge test displays a YES status (indicating that the purge 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 purge 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 MIL/System Status 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. For additional information on check mode operation refer to Powertrain Control Module Diagnosis.
This step checks for leaks in the fuel supply system. By plugging the ORVR vent line and the EVAP vapor line, the fuel tank, the fuel filler hose assembly, and the fuel tank components can be pressurized and checked for leaks. Be sure to check all connections and sealing points for leaks.
Step | Action | Value(s) | Yes | No | ||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | |||||||||||||
2 |
Is a DTC P0450 present? | -- | ||||||||||||
3 | Is a DTC P0441 or P0446 set along with the DTC P0440? | -- | Diagnose the P0441 or P0446 DTC First | |||||||||||
4 |
Was repair necessary? | -- | ||||||||||||
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) | |||||||||||||
Does the DMM read within the specified value? | 3.0-3.6 volts | |||||||||||||
Is the voltage indicated by the DMM within the second specified value? | 8.5-10.5 mm Hg (4.5-5.5 in. H2O) 4.2-4.6 volts | |||||||||||||
8 |
Was a repair necessary? | -- | ||||||||||||
9 |
Is the voltage within the specified value? | 3.0-3.6 volts | ||||||||||||
Is the action complete? | -- | -- | ||||||||||||
11 |
Does the DMM read the specified value? | 5.0 volts | ||||||||||||
12 | Measure the voltage from the fuel tank pressure sensor connector cavity 2 (harness side) with a DMM. Does the DMM read near the specified value? | 4.9 volts | ||||||||||||
13 |
Was a repair necessary? | -- | ||||||||||||
14 |
Was a repair necessary? | -- | ||||||||||||
15 | Probe the fuel tank pressure sensor connector cavity 1 (harness side) with a test lamp connected to battery voltage. Does the test lamp illuminate? | -- | ||||||||||||
16 |
Was a repair necessary? | -- | ||||||||||||
Did a DTC P0440 set? | -- | Fault Not Present-Go to Diagnostic Aids | ||||||||||||
18 | Refer to the Evaporative Emission Control System Operation Description for the EVAP system hose routing schematic used in the following procedure.
Were any EVAP or fuel supply system leaks found? | 56 mm Hg (30 in. H2O) | ||||||||||||
19 | Replace the malfunctioning/leaking EVAP canister. Is the action complete? | -- | -- | |||||||||||
20 | Repair or replace the leaking EVAP system or fuel tank component. Is the action complete? | -- | -- | |||||||||||
21 | Replace the fuel tank pressure sensor. Refer to Fuel Tank Pressure Sensor Replacement . Is the action complete? | -- | -- | |||||||||||
22 | Replace the PCM. Refer to Powertrain Control Module Replacement . Is the action complete? | -- | -- | |||||||||||
23 |
Are any DTCs displayed on scan tool? | -- | Go to the applicable DTC table | System OK |