Diagnostic Trouble Code (Dtc) P0446 Evap Canister Vent Blocked - Isuzu Trooper 1999 Workshop Manual

Diagnostic Trouble Code (DTC) P0446 EVAP Canister Vent Blocked

Circuit Description
The evaporative system
components:
f Fuel tank
f EVAP canister vent solenoid
f Fuel tank pressure sensor
f Fuel pipes and hoses
f Vapor lines
f Fuel cap
f Evaporative emissions canister
f Purge lines
f 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:
f Faulty EVAP canister vent solenoid (stuck closed).
f Plugged, kinked or pinched vent hose.
f Shorted EVAP canister vent solenoid driver circuit.
f Plugged evaporative canister.
If any of these conditions are present, DTC P0446 will set.
Conditions for Setting the DTC
f No TP sensor, ODM, IAT sensor, or MAP sensor DTCs
set.
f Start-up engine coolant temperature is less than 32°C
(90°F).
f Start-up engine coolant temperature is not more than
7°C (13°F) greater
temperature.
f Start-up intake air temperature is greater than 4°C
(39°F) .
f Start-up intake air temperature is not more than 2°C
(4°F) greater than
temperature.
f Vehicle speed is less than 75 mph (120 km/h).
f Throttle position is greater than 7% but less than 30%.
f Minimal fuel slosh.
f Fuel tank level is between 15% and 85%.
f BARO is greater than 75 kPa.
f Fuel tank pressure is not between –1.5 and 1.5 in. H2O
when ignition is turned "ON."
OR
f No TP sensor, ODM, IAT sensor, or MAP sensor DTCs
set.
TROOPER 6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
includes the following
than start-up intake
start-up engine coolant
f DTC P0442 diagnostic test has passed.
f Normal system operation is commanded (EVAP
canister vent solenoid open, EVAP canister purge
solenoid normal).
f Fuel tank pressure is less than –10 in. H2O.
f Above conditions are present for 60 to 180 seconds.
Action Taken When the DTC Sets
f The PCM will illuminate the MIL during the second key
cycle in which the DTC sets.
f 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
f 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.
f A history DTC P0446 will clear after 40 consecutive
warm-up cycles have occurred without a fault.
f DTC P0446 can be cleared by using the Tech 2 "Clear
Info" function or by disconnecting the PCM battery
feed.
Diagnostic Aids
Check for the following conditions:
f 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.
f 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.
f 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
air
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.
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.
6E–347