Isuzu 4HL1, Workshop Manual

Page: 67 / 267

Engine Control System 1A-65
F3: Actuator
Test F1: Injector
Balance Test This test aims at checking the injector drive signals are correctly sent to injectors
to operate the devices accordingly.
Test procedure:
1. Select "Injector Balance Test" from "Actuator Test".
2. Press "Next" soft key to select the injector number.
3. Press "Off" soft key to check the data list and vehicle condition.
4. When the vehicle condition changes as shown below, the injector control is
correctly performed.
Test result:
When the injector stops, the fuel injection to the relevant cylinder stops and
change in engine speeds is observed.
When a fault
is found in
"F1: Injector
Balance Test" Possible causes:
1. The injector system is shorted.
2. The injector is aged. (Check the cylinder-to-cylinder calibration on the data list
and determine functions of the injector.)
3. The fuel pipe is collapsed. Foreign materials are mixed.
4. The fuel injection is restricted due to operation of flow damper. (After the engine
is left inoperative for about 8 hours, and the injector is retested and the fault does
not occur, the cause lies in operation of flow damper.)
F2: Intake
Throttle Test This test aims at checking the working condition of the intake throttle valve and
ITP (intake throttle position) sensor.
Test procedure:
1. Select "Intake Throttle Test" from "Actuator Test".
2. Press "Decrease" or "Increase" soft key to check the data list.
3. When the data list changes as shown below, the intake throttle control is
correctly performed.
Test result:
Item Increase
instruction
Decrease
instruction
Desired Intake Air Throttle Position (°C A) Decrease Increase
Actual Intake Throttle Position (°C A) Decrease Increase
Intake Throttle Duty Ratio (%) Increase Decrease
Intake Throttle Valve (V) Decrease Increase
Difference Between Desired And Actual Values (°C A) within ±1
When a fault
is found in
"F2: Intake
Throttle Test" When a fault is found in this test, identify regular error, irregular error, or fixed
indication.
Possible causes:
1. The desired intake air throttle position is fixed (no change):
Tech 2 communication error occurs or the ECM is faulty.
2. The actual intake throttle position does not follow the desired intake throttle
position:
• Following under regular error = The problem lies in accuracy of ITP sensor.
• Following under irregular error = The problem lies in deformed intake throttle
valve, stain, foreign material mixing-in, unstable or aged motor power supply,
unstable battery voltage, aged motor functions, or electrical or mechanical noise.
• Fixed indication of actual intake throttle position = The problem lies in shorted
ITP sensor system, faulty sensor, stuck intake throttle valve, or faulty motor.