Isuzu 1999 RODEO Workshop Manual page 879

6E1–252 RODEO X22SE 2.2L ENGINE DRIVEABILITY AND EMISSION
f The difference between the actual Fuel Tank Pressure
and the expected Fuel Tank Pressure is less than the
PCM's expectations.
The above conditions are met, and the following condition
is met once:
f The EVAP system is unable to achieve or maintain
vacuum during the diagnostic test. The amount of
decay will vary with the fuel level.
Action Taken When the DTC Sets
f The Malfunction Indicator Lamp (MIL) will illuminate.
f The PCM will disable the EVAP purge vale solenoid.
f The PCM will record operating conditions at the time
the diagnostic fails. The Freeze Frame and Failure
Records buffers will store this information.
f A history Diagnostic Trouble Code is stored.
Conditions for Clearing the MIL/DTC
f The MIL will turn OFF after one ignition cycle in which
the diagnostic runs without a fault.
f Freeze Frame information and the history Diagnostic
Trouble Code will clear after one ignition cycle in which
the diagnostic runs without a fault.
f Diagnostic Trouble Codes can be cleared with the
Scan Tool's "Clear Info" function.
Diagnostic Aids
Check for the following conditions:
f A missing, loose, or damaged fuel cap.
f Missing or damaged O–rings at the EVAP canister fuel
vapor fittings and the purge line fittings.
f A cracked EVAP canister.
f Damaged or disconnected source vacuum line. EVAP
purge line, vent hose or fuel tank vapor line.
f The Fuel Pressure Sensor shares a 5 Volt reference
with the MAP sensor and TP sensor.
If these codes are also set, it could indicate a
problem with the 5 Volt reference circuit or
components itself.
f The Fuel Pressure Sensor share a ground with the
MAP sensor and the TP sensor.
f A poor connection at the PCM: Inspect the harness
connectors for backed out terminals, improper mating,
broken locks, improperly formed or damaged
terminals.
f Damaged harness: Inspect the wiring harness to the
EVAP vent solenoid, the EVAP purge solenoid, and the
fuel tank pressure sensor for shorts to ground, shorts
to battery positive and open circuits.
f A kinked, pinched or plugged vacuum source, EVAP
purge, or fuel tank vapor line. Verify that the lines are
not restricted.
Check for charcoal particles. Refer to Carbon Particles
Removal from EVAP System before starting repairs.
Reviewing the Fail Records vehicle mileage since the
diagnostic test last failed may help determine how often
the condition that caused the Diagnostic Trouble Code to
set occurs. This may assist in diagnosing the condition.
Test Description
Number(s) below refer to the step number(s) on the
Diagnostic Chart:
1. The Powertrain OBD System Check prompts the
technician to complete some basic checks and store
the freeze frame and failure records data on the
Tech 2 if applicable. This creates an electronic copy
of the data taken when the malfunction occurred.
The information is then stored on the Tech 2 for
later reference.
4. If a vent solenoid or EVAP canister purge valve
electrical malfunction is present, the purge system
will not operate correctly. Repairing the electrical
malfunction will very likely correct the condition that
set Diagnostic Trouble Code P0440.
5. Check the fuel tank pressure sensor at ambient
pressure.
7. Forces the fuel tank pressure sensor to re–zero.
8. Determines whether or not the EVAP system is
sealed sufficiently to be pressurized. If not, the
large leak must be located and corrected before
continuing with diagnosis.
9. Verifies that the fuel tank pressure sensor
accurately reacts to EVAP system pressure
changes.
12. Ensures that sufficient source vacuum is present at
the EVAP canister purge valve.
13. Check for a stuck closed EVAP canister purge
valve.
20. Insures proper system integrity.