P0446
DTC P0446 EVAP Canister Vent Blocked
Circuit Description
The evaporative system includes the following components:
- Fuel tank
- EVAP canister vent solenoid
- Fuel tank pressure sensor
- Fuel pipes and hoses
- Vapor lines
- Fuel cap
- Evaporative emissions canister
- Purge lines
- EVAP canister purge solenoid
An incorrect fuel tank pressure sensor signal is detected by monitoring fuel tank pressure when the key is first turned ON during a cold start. If the fuel tank pressure signal is out of range, DTC P0446 will set. A restricted or blocked EVAP vent path is detected by monitoring fuel tank pressure during normal operation (EVAP canister vent solenoid open, EVAP canister purge solenoid normal). With the EVAP canister vent solenoid open, vacuum level in the system should be very low unless the vent path is blocked. A blockage can be caused by the following condition:
- Faulty EVAP canister vent solenoid (stuck closed).
- Plugged, kinked or pinched vent hose.
- Shorted EVAP canister vent solenoid driver circuit.
- Plugged evaporative canister.
If any of these conditions are present, DTC P0446 will set.
Conditions for Setting the DTC
- No TP sensor, 0DM, IAT sensor, or MAP sensor DTCs set.
- Start-up engine coolant temperature is less than 32 °C (90 °F).
- Start-up engine coolant temperature is not more than 7 °C (13 °F) greater than start-up intake air temperature.
- Start-up intake air temperature is greater than 4 °C (39 °F)
- Start-up intake air temperature is not more than 2 °C (4 °F) greater than start-up engine coolant temperature.
- Vehicle speed is less than 75 mph (120 kph).
- Throttle position is greater than 7% but less than 30%.
- Minimal fuel slosh.
- Fuel tank level is between 15% and 85%.
- BARO is greater than 75 kPa.
- Fuel tank pressure is not between -1.5 and 1.5 in. H2O when ignition is turned ON.
OR
- No TP sensor, 0DM, IAT sensor, or MAP sensor DTCs set.
- DTC P0442 diagnostic test has passed.
- Normal system operation is commanded (EVAP canister vent solenoid open, EVAP canister purge solenoid normal).
- Fuel tank pressure is less than -10 in. H2O.
- Above conditions are present for 60 to 180 seconds.
Action Taken When the DTC Sets
- The PCM will illuminate the MIL during the second key cycle in which the DTC sets.
- The PCM will store conditions which were present when the DTC set as Freeze Frame and Failure Records data.
Conditions for Clearing the MIL/DTC
- The PCM will turn the MIL OFF on the third consecutive trip cycle during which the diagnostic has been run and the fault condition is no longer present.
- A history DTC P0446 will clear after 40 consecutive warm-up cycles have occurred without a fault.
- DTC P0446 can be cleared by using the scan tool Clear Info function or by disconnecting the PCM battery feed.
Diagnostic Aids
Check for the following conditions:
- Poor connection at PCM - Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection.
- Damaged harness-Inspect the wiring harness to the EVAP canister vent solenoid, EVAP canister purge solenoid and the fuel tank pressure sensor for an intermittent open or short circuit.
- Kinked, pinched, or plugged vent hose-Verify that the vent hose between the EVAP canister and EVAP canister vent solenoid is not restricted.
Reviewing the Failure Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition.
Steps 1 - 3:
Steps 4 - 6:
Steps 7 - 10:
Test Description
Number(s) below refer to the step number(s) on the Diagnostic Chart.
2. If a vent solenoid electrical fault is present, the purge system will not operate correctly. Repairing the electrical fault will very likely correct the condition that set DTC P0446.
3. Checks the fuel tank pressure sensor at ambient pressure.
4. Verifies that the fuel tank pressure sensor accurately reacts to EVAP system pressure changes.
6. Checks for a blocked EVAP canister.