The Leak Test:
- The test is based on applying a vacuum to the system and
monitoring the vacuum over time.
- The Power train Control Module (PCM or "computer") monitors the vacuum level
through a Fuel Tank Sensor.
- After some time, the EVAP canister purge
valve/solenoid & EVAP vent valve/solenoid are turned ON, allowing the engine
vacuum to draw a small vacuum on the entire evaporative emission system.
- If a
sufficient vacuum level cannot be achieved, or decreases too fast, a "large leak" or faulty purge
valve/solenoid is detected and could set the P0440 code.
This can be caused by any of the following conditions:
- Leaking fuel tank or fuel filler
neck.
-
Leaking fuel sender assembly
O-ring.
-
Disconnected or faulty fuel tank
pressure sensor.
-
Missing, not completely installed
or faulty fuel fill cap.
- Disconnected, damaged, pinched, or
blocked purge line.
-
Disconnected or damaged EVAP vent
hose.
- Disconnected, damaged, pinched, or
blocked fuel tank vapor line.
-
Disconnected or faulty
canister purge valve/solenoid.
- Disconnected or malfunctioning vent valve/solenoid.
-
Open ignition feed circuit to the
vent or purge valve/solenoid.
- Damaged EVAP canister.
Conditions for the test to run (by the control system):
- Certain DTCs are NOT set (from TP sensor, IAT sensor, or
MAP sensors)
- System voltage is between 10 & 16 volts.
- Fuel tank fuel level is between 15% & 85%.
- The barometric Pressure (BARO) is more than 75 kPa.
- The Intake Air Temperature (IAT) is between 40°F and 86°F.
- The Engine Coolant Temperature (ECT) is between 40°F & 86°F.
- The startup IAT & ECT are within 16°F of each other.
Clearing the code or turning OFF the Malfunction Indicator Lamp
(MIL):
- The code will clear if the fill cap is tightened or reinstalled.
- This DTC can be cleared by using the scan tool Clear Info function or by
disconnecting the PCM battery feed.
- The PCM will turn the MIL OFF when the diagnostic has been run & the fault
condition is no longer present.
- A "history" DTC P0440 will clear after 40 consecutive warm-up cycles have
occurred without a fault.
Notes:
- The control module will illuminate the Malfunction Indicator Lamp
(MIL) during the 2nd consecutive trip in which the diagnostic
is run and fails.
- The system will store conditions present when the DTC set as Freeze
Frame/Failure Records data. |
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