Isuzu 4HL1 Workshop Manual page 180

1A-178 Engine Control System
Circuit Description
The common rail pressure is detected by the common
rail pressure sensor and sent to the ECM. The ECM
calculates the desired common rail pressure and pump
flow rate from the data sent from sensors and
compares these calculations with the actual common
rail pressure to determine the SCV position.
DTC118 will be set when the common rail pressures is
excessively high.
Major Faulty Event
• Poor startability
• Generation of while/black smoke
• Short power
• Poor driveability
Conditions for Setting the DTC
The state where the common rail pressure output
voltage is in normal condition and the actual common
rail pressure is at least 180 MPa lasts 5 times
continuously.
Action Taken When the DTC Sets
• After the DTC is set, the ECM will illuminate the
CHECK ENGINE lamp (MIL).
• The ECM prepares for engine shutdown.
25 6 8 27 26
CKP CMP
Sensor Sensor
63 66 6764
69 68
ITP EGR Valve
Sensor Position
Sensor
Conditions for Clearing MIL/DTC
When the system fails and the DTC is stored to the
ECM, even repairing the faulty portion will not clear the
DTC from the memory. To clear the DTC, conduct the
following steps.
1. Turn off the idle position switch for not less than 1
second but not more than 3 seconds. (Press the
accelerator pedal.)
2. Turn on the idle position switch for not less than 1
second but not more than 3 seconds. (Release the
accelerator pedal.)
3. Turn off the idle position switch for not less than 1
second but not more than 3 seconds. (Press the
accelerator pedal.)
4. Turn on the idle position switch for not less than 1
second but not more than 3 seconds. (Release the
accelerator pedal.)
5. Turn off the idle position switch for not less than 1
second but not more than 3 seconds. (Press the
accelerator pedal.)
6. After the above operations are properly completed,
the CHECK ENGINE lamp (MIL) illuminates for 3
seconds to report the memory is cleared.
7. Turn off the starter switch. Wait for 5 seconds and
turn on the starter switch again.
When Tech 2 has been connected to the vehicle, the
DTC can be cleared through the memory clear
operation with Tech 2.
ECM
(Engine
Control
Module)
Common
Rail
Pressure
Sensor
LNW21AMF006901-X