Ecm Data - Isuzu 4HL1 Workshop Manual

1A-76 Engine Control System
Tech 2 Engine Data Description

ECM Data

Tech 2 Data
Item
Display
1/63 System Voltage
2/63 Vehicle Speed
3/63 Desired Idle
Speed
4/63 Engine Speed
5/63 Accelerator
Sensor
6/63 Final Accelerator
Opening
Units
displayed
V This parameter refers to the
power supply voltage applied to
the ECM from the battery.
km/h This parameter refers to the
value calculated by the ECM
using the signals from the VS
sensor.
RPM This parameter refers to the
value calculated by the ECM
using ECT and vehicle condition
(with respect to automatic
transmission, air conditioner,
QWS, freezer, idle up volume,
PTO, and neutral switch).
RPM This parameter refers to the
value calculated by the ECM
using the signals from CKP
(crank position) and CMP (cam
position) sensors.
V This parameter refers to the
signal voltage input to the ECM
from the AP (accelerator pedal
position) sensor.(Larger
accelerator pedal stroke provides
higher voltage.)
% This parameter refers to the
value calculated by the ECM
using the signals from the AP
sensor.
Description How to use parameters
When the display substantially
deviates from the actual battery
voltage, a voltage drop may
occur due to accessories
installed to the circuit. If the value
deviates from the specified level,
the circuit, connector, connector
mating, or ECM may be faulty.
When the display differs from the
speedometer reading or is
unchanged, major cause may lie
in VS sensor, circuit, or ECM.
When the required idle speed is
unstable, the cause may lie in
improperly installed ECM or
sensors (such as improper
connector mating or deformed
connector pins), or ECM or
sensor signal faults. When the
idle speed becomes unstable
after vibrations are applied to the
wiring harness, the cause may be
faulty harness or imperfect
connection of ground circuit.
This parameter should be used
by comparing to the desired idle
speed. Using the display needs
those conditions: the engine is
completely warmed up, all the
accessory systems, including air
conditioner, are turned off, and
the idle speed is stabilized. The
actual idle speed is stabilized
near the desired level. After the
load such as air conditioner is
added, the engine speed is
changed but finally stabilized.
When AP sensor's signal voltage
(accelerator pedal position)
deviates from the specified level
as the accelerator pedal press-
down stroke is changed, the
sensor, circuit, or ECM may be
faulty.
When AP sensor's signal voltage
(Final Accelerator Opening)
deviates from the specified level
as the accelerator pedal press-
down stroke is changed, the
sensor, circuit, or ECM may be
faulty.