Isuzu 1999 RODEO Workshop Manual page 697

6E1–70
RODEO X22SE 2.2L ENGINE DRIVEABILITY AND EMISSION
EVAP PURGE PWM – Tech 2 Range 0%–100%
Represents the PCM commanded PWM duty cycle of the
EVAP purge solenoid valve. "0%" displayed indicates no
purge; "100%" displayed indicates full purge.
EVAP VACUUM SWITCH – Tech 2 Displays PURGE
or NO PURGE
The EVAP purge vacuum switch is a normally closed
switch positioned in the purge line between the canister
and the EVAP purge solenoid. The EVAP purge vacuum
switch will open when vacuum increases to greater than
5 inches of water in the purge line. The EVAP purge
vacuum switch is used by the PCM to monitor EVAP
canister purge solenoid operation and purge system
integrity. The EVAP purge vacuum switch should be
closed to ground with no vacuum present (0% EVAP
purge PWM). With EVAP purge PWM at 25% or greater,
the EVAP purge vacuum switch should be open and
"PURGE" should be indicated.
FUEL PUMP – Tech 2 Displays ON or OFF
Indicates the PCM commanded state of the fuel pump
relay driver circuit.
FUEL TRIM CELL – Tech 2 Range 0–21
The fuel trim cell is dependent upon engine speed and
MAF sensor readings. A plot of RPM vs. MAF is divided
into 22 cells. Fuel trim cell indicates which cell is currently
active.
FUEL TRIM LEARN – Tech 2 Displays NO or YES
When conditions are appropriate for enabling long term
fuel trim corrections, fuel trim learn will display YES. This
indicates that the long term fuel trim is responding to the
short term fuel trim. If the fuel trim learn displays NO, then
long term fuel trim will not respond to changes in short
term fuel trim.
GENERATOR CONTROL – Tech 2 Displays ACTIVE
or INACTIVE.
HO2S BANK 1, SEN. 1 – Tech 2 Range 0–1000 mV
Represents the fuel control exhaust oxygen sensor
output voltage. Should fluctuate constantly within a range
between 10 mV (lean exhaust) and 1000 mV (rich
exhaust) while operating in "Closed Loop".
HO2S BANK 1, SEN. 2 – Tech 2 Range 0–1000 mV
Represents the exhaust oxygen sensor output voltage.
Should fluctuate constantly within a range between 10
mV (lean exhaust) and 1000 mV (rich exhaust) while
operating in "Closed Loop". This is used along with HO2S
Bank 1, Sensor 3 to determine the catalytic converter
efficiency in the manual transmission models.
HO2S BANK 1, SEN. 1 – Tech 2 Displays NOT
READY or READY
Indicates the status of the exhaust oxygen sensor. The
Tech 2 will indicate that the exhaust oxygen sensor is
ready when the PCM detects a fluctuating HO2S voltage
sufficient to allow "Closed Loop" operation. This will not
occur unless the exhaust sensor is warmed up.
HO2S WARM UP TIME BANK 1, SEN. 1 – Tech 2
Range 00:00:00–99:99:99 HRS:MIN:SEC
Indicates warm–up time for each HO2S. The HO2S
warm–up time is used for the HO2S heater test. The PCM
will run the heater test only after a cold start (determined
by engine coolant and intake air temperature at the time
of start–up) and only once during an ignition cycle. When
the engine is started the PCM will monitor the HO2S
voltage. When the HO2S voltage indicates a sufficiently
active sensor, the PCM looks at how much time has
elapsed since start–up. If the PCM determines that too
much time was required for the HO2S to become active,
a DTC will set. If the engine was warm when started,
HO2S warm–up will display "00:00:00."
IAC POSITION – Tech 2 Range 0–255 Counts
Displays the commanded position of the idle air control
pintle in counts. A larger number of counts means that
more air is being commanded through the idle air
passage. Idle air control should respond fairly quickly to
changes in engine load to maintain desired idle RPM.
IAT (INTAKE AIR TEMPERATURE) – Tech 2 Range
–40°C to 151°C (–40°F to 304°F)
The PCM converts the resistance of the intake air
temperature sensor to degrees. Intake air temperature
(IAT) is used by the PCM to adjust fuel delivery and spark
timing according to incoming air density.
IGNITION 1 – Tech 2 Range 0–25.5 Volts
This represents the system voltage measured by the
PCM at its ignition feed.
INJ. PULSE BANK 1 – Tech 2 Range 0–1000 msec.
Indicates the amount of time the PCM is commanding
each injector ON during each engine cycle. A longer
injector pulse width will cause more fuel to be delivered.
Injector pulse width should increase with increased
engine load.
LONG TERM FUEL TRIM BANK 1
The long term fuel trim is derived from the short term fuel
trim values and represents a long term correction of fuel
delivery for the bank in question. A value of 0% indicates
that the fuel delivery requires no compensation to
maintain the PCM commanded air/fuel ratio. A negative
value significantly below 0% indicates that the fuel
system is rich and fuel delivery is being reduced
(decreased injector pulse width). A positive value
significantly greater than 0% indicates that a lean
condition exists and the PCM is compensating by adding
fuel (increased injector pulse width). Because long term
fuel trim tends to follow short term fuel trim, a value in the
negative range due to canister purge at idle should not be
considered unusual. Fuel trim values at maximum
authority may indicate an excessively rich or lean system.
LOOP STATUS – Tech 2 Displays OPEN or CLOSED
"CLOSED" indicates that the PCM is controlling fuel
delivery according to oxygen sensor voltage. In "OPEN"
the PCM ignores the oxygen sensor voltage and bases
the amount of fuel to be delivered on TP sensor, engine
coolant, and MAF sensor inputs only.