Isuzu 4HL1 Workshop Manual page 175

Circuit Description
The common rail pressure sensor detects the fuel
pressure in the common rail and outputs the voltage
equivalent to the common rail pressure. Higher
pressure provides higher voltage while lower pressure
provides lower voltage. The ECM calculates the actual
common rail pressure (fuel pressure) from the voltage
signal sent from the sensor and uses the result in fuel
injection control and other control tasks.
DTC115 will be set when the difference between
desired and actual common rail pressures is large and
the sensor output voltage is fixed to a certain value.
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 sensor is in
normal condition, there is no change in common rail
pressure sensor output voltage, the difference between
desired and actual common rail pressures is 10 MPa or
more, the actual common rail pressure is 10 MPa or
more, and the pump is under feedback control is
continuously observed
conversion in the ECM.
25 6 8 27 26
CKP CMP
Sensor Sensor
255 times during
63 66 6764
69 68
ITP EGR Valve
Sensor Position
Sensor
Action Taken When the DTC Sets
• After the DTC is set, the ECM will illuminate the
CHECK ENGINE lamp (MIL).
• The common rail pressure and fuel injection
quantity are limited.
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.)
A/D
6. After the above operations are properly completed,
the CHECK ENGINE lamp (MIL) illuminates for 3
seconds to report the memory is cleared.
Engine Control System 1A-173
ECM
(Engine
Control
Module)
Common
Rail
Pressure
Sensor
LNW21AMF006901-X