Isuzu 2000 Trooper Workshop Manual page 1205

6E–336
TROOPER 6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
D 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:
D 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.
D 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.
D 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
Step
1 Was the "On-Board Diagnostic (OBD) System Check"
performed?
2 1. Ignition "ON."
2. Capture Failure Records data for DTC P0446 and
clear DTCs.
3. Ignition "OFF."
4. Remove the fuel cap.
5. Ignition "ON."
6. Observe "Fuel Tank Pressure" on the Tech 2.
Does Tech 2 indicate "Fuel Tank Pressure" at the
specified value?
3 IMPORTANT: Before continuing with diagnosis, zero
the EVAP pressure and vacuum gauges on the EVAP
pressure/purge cart J 41413 (refer to tool operating
instructions).
1. Replace the fuel cap.
2. Using the Tech 2, command the EVAP vent solenoid
"ON" (closed).
3. Connect the EVAP pressure/purge cart J 41413 to
the EVAP service port.
4. Using the EVAP pressure/purge cart J 41413,
pressurize the EVAP system to the specified value.
5. Observe "Fuel Tank Pressure" on the Tech 2.
Does Tech 2 indicate "Fuel Tank Pressure" at the
specified value?
4 1. Maintain the EVAP pressure at 5 in. at H2O.
2. Using Tech 2, command the EVAP vent solenoid
"OFF" (open) while observing the EVAP pressure
gauge on the cart J 41413.
Does the EVAP pressure return to the specified value
within 5 seconds?
DTC P0446– EVAP Canister Vent Blocked
Action
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.
Value(s)
— Go to Step 2
1.51V Go to Step 3
Go to Step 4
1.52 – 1.69V
Diagnostic
0 in. H2O
Yes No
Go to OBD
System
Check
Go to Fuel
Tank
Pressure
System
Go to Fuel
Tank
Pressure
System
Refer to
Aids
Go to Step 5