Isuzu C22NE Workshop Manual page 241

ENGINE SCAN TOOL DATA
DEFINITIONS AND RANGES
A/C CLUTCH - Scan Tool Displays ON or OFF -
Indicates whether the ECM has commanded the A/C
clutch ON. Used in A/C system diagnostics.
A/C REQUEST - Scan Tool Displays NO or OFF -
Indicates the state of the A/C request input circuit from
the HVAC controls. The ECM uses the A/C request
signal to determine whether A/C compressor operation
is being requested.
AIR/FUEL RATIO - Scan Tool Range 0-0:1-25.5:1 -
Air/fuel ratio indicates the ECM commanded value. In
"Closed Loop" , the air/fuel ratio should normally be
displayed around "14.2-14.7" . A lower air/fuel ratio
indicates a richer commanded mixture, which may be
seen during power enrichment or TWC (If applicable)
protection modes. A higher air/fuel ratio indicates a
leaner commanded mixture. This can be seen during
deceleration fuel mode.
BARO kPa - Scan Tool Range 10-105 - The
barometric pressure reading is determined from the
MAP sensor signal monitored during key up and wide
open throttle (WOT) conditions. The barometric
pressure is used to
differences and is normally displayed around "61-104"
depending on altitude and barometric pressure.
DECELERATION FUEL CUT OFF - YES or NO-
Scan Tool Displays - "ACTIVE" displayed indicates
that the ECM has detected conditions appropriate to
operate in deceleration fuel mode. The ECM will
command the deceleration fuel mode when it detects
a closed throttle position while the vehicle is traveling
over 20 mph. While in the deceleration fuel mode, the
ECM will decrease the amount of fuel delivered by
entering "Open Loop" and decreasing the injector
pulse width.
DESIRED IDLE - Scan Tool Range 0-3187 RPM -
The idle speed that the ECM is commanding. The
ECM will compensate for various engine loads based
on engine coolant temperature, to keep the engine at
the desired speed.
ECT TEMP. - (Engine Coolant Temperature) Scan
Tool Range − − − − 40°C to 151°C (− − − − 40°F to 304°F) - The
engine coolant temperature (ECT) is mounted in the
coolant stream and sends engine temperature
information to the ECM. The ECM applies 5 volts to
the ECT sensor circuit. The sensor is a thermistor
which changes internal resistance as the temperature
changes. When the sensor is cold (high resistance),
compensate for altitude
DRIVEABILITY AND EMISSIONS 6E1-71
the ECM monitors a high signal voltage and interprets
that as a cold engine. As the sensor warms
(decreasing resistance), the voltage signal will
decrease and the ECM will interpret the lower voltage
as a warm engine.
TIME FROM START - Scan Tool Range 00:00:00-
99:99:99 Hrs:Min:Sec - Indicates the time elapsed
since the engine was started. If the engine is stopped,
engine run time will be reset to 00:00:00.
ENGINE SPEED - Range 0-9999 RPM - Engine
speed is computed by the ECM form the 58X
reference input. It should remain close to desired idle
under various engine loads with engine idling.
EVAP PURGE PWM (If applicable) - Scan Tool
Range 0%-100% - Represents the ECM commanded
PWM duty cycle of the EVAP purge solenoid valve.
"0%" displayed indicates no purge; "100%" displayed
indicates full purge.
FUEL PUMP RELAY - Scan Tool Displays ON or
OFF - Indicates the ECM commanded state of the fuel
pump relay driver circuit.
02 BLM CELL NUMBER (If applicable)- Scan Tool
Range 0-21 - The 02 BLM cell is dependent upon
engine speed and MAP sensor readings. A plot of
RPM vs. MAP is divided into 22 cells. 02 BLM cell
indicates which cell is currently active.
B1 HO2S BANK 1 (If applicable)- Scan Tool 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" .
B1 HO2S READY BANK 1 (If applicable)- Scan Tool
Displays YES or NO - Indicates the status of the
exhaust oxygen sensor. The Scan Tool will indicate
that the exhaust oxygen sensor is ready when the
ECM detects a fluctuating HO2S voltage sufficient to
allow "Closed Loop" operation. This will not occur
unless the exhaust sensor is warmed up.
IAC CONTROL STEP - Scan Tool Range 0-255
steps - 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) - Scan Tool
Range − − − − 40°C to 151°C (− − − − 40°F to 304°F) - The ECM
converts the resistance of the intake air temperature
sensor to degrees. Intake air temperature (IAT) is