Isuzu 4HL1 Workshop Manual page 176

1A-174 Engine Control System
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.
Diagnostic Aids
When the air mixes into the fuel system, the fuel
pressure (common rail pressure) may read incorrect
value. If air bleed resolves the fault, the possible cause
is the air mixing into fuel system.
Step
Perform the "On-Board Diagnostic (OBD)
System Check".
1
Was the OBD System Check performed?
Review the DTC.
1. Using Tech 2, check and store the DTC.
2. Clear the DTC.
2
3. Bleed the air from the fuel system.
4. Perform test run and review the DTC.
Is DTC115 detected?
Check the common rail pressure.
1. Install Tech 2.
2. Starter switch "ON".
3. Observe "Desired Rail Pressure" and
"Actual Rail Pressure" displays .
4. Start and idle the engine for warm-up.
5. Observe "Desired Rail Pressure" and
3
"Actual Rail Pressure" displays again.
Does the actual common rail pressure
increase following the desired pressure?
Check the ECM for fault.
1. Starter switch "ON", engine "OFF".
2. Disconnect the common rail pressure
sensor connector.
3. On Tech 2, observe the "Common Rail
Pressure Sensor" display for output
voltage.
4
CAUTION:
After the common rail pressure sensor is
disconnected, DTC245 is set. Be sure to
clear this DTC245 upon completion of this
Step 4.
Was the voltage within range?
Action
Test Description
5. When the common rail pressure sensor harness and
other sensor harness are shorted, DTC245 may not be
set.
Value(s)
—
Go to Step 2
—
Go to Step 3
Engine off:
Desired
pressure -
0 MPa
Actual
pressure -
0 MPa
Idling:
Desired
pressure -
Approx.
40 MPa
Actual
pressure -
Approx.
40 MPa Go to Step 8
Approx. 0 V
Go to Step 8
Yes No
Refer to OBD
System Check
and go to Step 2
Refer to
Diagnostic Aids
Go to Step 4
Go to Step 5