Isuzu 4HL1 Workshop Manual page 255

Symptom Diagnosis Chart 2
1 Common rail pressure sensor
2 ECT sensor
IAT sensor
FT sensor
3 AP sensor
4 PTO accelerator sensor
5 VS sensor
1 Idle position switch (the switch is closed at
idle and opened after the accelerator pedal is
pressed)
2 Starter switch (N/O)
A: sensor system
1. With the starter switch turned on and engine warmed up,
observe "Desired Rail Pressure" and "Actual Rail Pressure"
displays on Tech 2.
Reference value: Starter switch ON: 0 MPa
Engine warmed up: approx. 40 MPa
• Under the
Temperature", "ECT Sensor", "Intake Air Temperature",
"Fuel Temperature", and "FT Sensor (Fuel Temperature)"
displays.
1. With the engine completely cooled down (the engine is
being shut down for at least 8 hours), check the voltages are
almost equivalent to the indicated temperatures for ECT,
IAT, and FT sensors, respectively.
2. With the engine completely warmed up (the engine coolant
temperature is about 80°C), measure the resistance of each
sensor and check the temperatures indicated on Tech 2 are
almost the same as the reference values. (For reference
values, refer to "DTC22 - IAT Sensor Fault", "DTC23 - ECT
Sensor Fault", and "DTC211 - Fuel Temperature Sensor
Fault".)
1. Check the accelerator pedal and surroundings for foreign
material and, if any, remove them.
2. Observe "Final Accelerator Opening" and "Accelerator
Pedal Position Sensor" displays while operating the
accelerator pedal.
Reference value: Idle position (0 %): approx. 0.6 V
WOT position (100 %): approx. 4.5 V
1. Check the external accelerator is not active and, if working,
release the accelerator.
2. Observe "PTO Accelerator Opening" and "PTO Accelerator
Sensor" displays.
Reference value: approx. 0.6 V (0 %)
1. Install Tech 2 and run the vehicle, and compare the engine
control parameter "Vehicle Speed" displayed on Tech 2 to
the vehicle's speedometer reading and also compare the
engine control parameter "Vehicle Speed" on Tech 2 to the
automatic transmission (if equipped) control parmeter
"Vehicle Speed" displayed on Tech 2.
2. Check above values are free from deviation each other.
B: Switch/relay system
1. With the accelerator pedal completely released, observe the
"Idle Position Switch" display.
2. If even pressing the accelerator pedal does not turn on the
switch, check the switch for foreign materials and, if any,
remove them. Test the single switch for continuity.
1. Move the starter switch to the "ST" position and observe the
"Starter Switch" display.
2. When the starter switch is not turned on, continuity-test the
circuit between starter switch and starter relay, as well as
single switch.
Engine Control System 1A-253
Inspection method
following conditions, observe "Coolant