Isuzu N-Series. Service manual — part 664

6E-78 Engine Control System (4HK1)

P1093

227

ON

Fuel Rail
Pressure (FRP)
Too Low

• DTCs P0090,

P0192, P0193,
P0201 – P0204,
P0611, P0612,
P1095, P1261,
P1262, P1630 and
P1635 are not set.

• The ignition switch is

ON.

• The ignition voltage

is more than 18
volts.

• The FRP regulator

command is less
than 33% or
commanded fuel
supply is more than
a predetermined
value.

Either of following
condition is met:

• The ECM detects

that the differential
fuel rail pressure is -
10 MPa (-1,450 psi)
for longer than 15
seconds when the
engine speed is
between 0 – 900
RPM.

• The ECM detects

that the deferential
fuel rail pressure is -
15 MPa (-2,170 psi)
for longer than 15
seconds when the
engine speed is
higher than 1200
RPM.

• Loss fuel or less fuel in

the fuel tank.

• Pressure limiter valve

opening pressure drop.

• Faulty fuel injector.
• Fuel suction side

looseness, kinks or
blocked.

• Faulty or clogged fuel

filter.

• FRP sensor circuit is

intermittently open
circuit, poor connection
or corrosion.

• FRP sensor circuit high

resistance.

• FRP regulator circuit is

intermittently open
circuit, poor connection
or corrosion.

• FRP regulator circuit

high resistance.

• Faulty FRP sensor.
• Faulty FRP regulator.
• Faulty fuel supply pump.

DTC

Flash
Code

MIL

Status

DTC Name

Condition for Running

the DTC

Condition for Setting the

DTC

Possible Cause

Engine Control System (4HK1) 6E-79

P1094

226

ON

Fuel Rail
Pressure (FRP)
Too Low

FRP Regulator
Command High DTC

• DTCs P0090,

P0117, P0118,
P0192, P0193,
P0201 – P0204,
P0500, P0501,
P0611, P0612,
P1095, P1261,
P1262, P1630 and
P1635 are not set.

• The ignition switch is

ON.

• The ignition voltage

is more than 18
volts.

• The engine is

running.

• The accelerator

pedal position is 0%.

• The engine coolant

temperature is more
than 50

°C (122°F).

• The vehicle speed is

less than 5 km/h (4
MPH).

• The engine speed

does not vary more
than 50 RPM.

FRP Drop DTC

• DTCs P0090,

P0192, P0193,
P0201 – P0204,
P0611, P0612,
P1095, P1261,
P1262, P1630 and
P1635 are not set.

• The ignition switch is

ON.

• The ignition voltage

is more than 18
volts.

• The engine is

running.

• The accelerator

pedal position is 0%.

• The engine coolant

temperature is more
than 50

°C (122°F).

• The vehicle speed is

more than 50 km/h
(30 MPH).

• The commanded

fuel injection
quantity is OFF.

FRP Regulator
Command High DTC

• The ECM detects

that the FRP
regulator
commanded fuel is
more than a
predetermined
range for longer than
15 seconds when
the engine speed is
between 600 – 1500
RPM.

FRP Drop DTC

• The ECM detects

that the FRP sensor
signal voltage is
shapely dropped
more than 0.2 volts
when the engine
cuts fuel.

• Fuel leaking at high

pressure side.

• Loss fuel or less fuel in

the fuel tank.

• Pressure limiter valve

opening pressure drop.

• Faulty fuel injector.
• Fuel suction side

looseness, kinks or
blocked.

• Faulty or clogged fuel

filter.

• FRP sensor circuit is

intermittently open
circuit, poor connection
or corrosion.

• FRP sensor circuit high

resistance.

• FRP regulator circuit is

intermittently open
circuit, poor connection
or corrosion.

• FRP regulator circuit

high resistance.

• Faulty FRP sensor.
• Faulty FRP regulator.
• Faulty fuel supply pump.

DTC

Flash
Code

MIL

Status

DTC Name

Condition for Running

the DTC

Condition for Setting the

DTC

Possible Cause

6E-80 Engine Control System (4HK1)

P1095

225

ON

Fuel Pressure
Limiter Activation

• DTCs P0192,

P0193, P1630 and
P1635 are not set.

• The ignition switch is

ON.

• The ignition voltage

is more than 18
volts.

• The ECM detects

that the FRP sensor
signal voltage drops
quickly from more
than 3.7 volts to less
than 2.3 volts, and
then the differential
fuel rail pressure is
more than -30 MPa
(4,350 psi).

• Loss fuel or less fuel in

the fuel tank.

• Faulty fuel injector.
• Fuel suction side

looseness, kinks or
blocked.

• Faulty or clogged fuel

filter.

• FRP sensor circuit is

intermittently open
circuit, poor connection
or corrosion.

• FRP sensor circuit high

resistance.

• FRP regulator circuit is

intermittently open
circuit, poor connection
or corrosion.

• FRP regulator circuit

high resistance.

• Faulty FRP sensor.
• Faulty FRP regulator.
• Faulty fuel supply pump.

P1173

542

OFF

Engine Overheat

• DTCs P0117,

P0118, P1630 and
P1634 are not set.

• The ignition switch is

ON.

• The ignition voltage

is more than 18
volts.

• The engine is

running.

• The ECM detects

that the engine
coolant temperature
is more than 110

°C

(230

°F) for 15

seconds.

• Engine overheat.
• Faulty engine cooling

system.

• Faulty engine coolant

temperature sensor.

P1220

28

ON

PTO Engine
Speed Selector
Sensor Circuit
High Voltage

• DTCs P1630 and

P1631 are not set.

• The ignition switch is

ON.

• The ignition voltage

is more than 18
volts.

• The ECM detects

that the PTO throttle
sensor signal
voltage is more than
4.8 volts.

• Sensor 5V reference

circuit is short to battery
or ignition voltage.
(P1631 may also set.)

• Sensor signal circuit is

short to battery, ignition
voltage or short to any
5V reference circuit.

• Sensor low reference

circuit is open circuit or
high resistance.

• Poor harness connector

connection.

• Faulty sensor.
• Faulty ECM.

DTC

Flash
Code

MIL

Status

DTC Name

Condition for Running

the DTC

Condition for Setting the

DTC

Possible Cause

Engine Control System (4HK1) 6E-81

P1225

31

ON

Engine Idle
Speed Selector
Sensor Circuit

• DTCs P1630 and

P1631 are not set.

• The ignition switch is

ON.

• The ignition voltage

is more than 18
volts.

Either of following
condition is met:

• The ECM detects

that the idle up
sensor signal
voltage is less than
0.1 volts for 5
second.

• The ECM detects

that the idle up
sensor signal
voltage is more than
4.9 volts for 5
second.

• Sensor 5V reference

circuit is short to battery
or ignition voltage, short
to ground or short to the
low reference circuit.
(P1631 may also set.)

• Sensor 5V reference

circuit is open circuit,
high resistance.

• Sensor signal circuit is

short to battery, ignition
voltage or short to any
5V reference circuit,
short to ground, short to
the low reference circuit,
open circuit or high
resistance.

• Sensor low reference

circuit is open circuit or
high resistance.

• Poor harness connector

connection.

• Faulty sensor.
• Faulty ECM.

P1261

158

ON

Injector Positive
Voltage Control
Circuit Group 1

• DTC P0611 is not

set.

• The ignition switch is

ON.

• The battery voltage

is more than 18
volts.

• The engine is

running.

Either of following
condition is met:

• The ECM detects

that the common 1
fuel injector drive
circuit is open circuit,
shorted to ground or
shorted to voltage
during engine
rotations.

• The ECM detects

that the cylinder #1
or #4 fuel injector
solenoid coil control
circuit is shorted to
ground during
engine rotations.

• Cylinder #1 or #4 fuel

injector solenoid coil
control circuit is short to
ground.

• Common 1 fuel injector

drive circuit is short to
battery, ignition voltage,
short to ground, open
circuit or high resistance.

• Faulty fuel injector.
• Faulty ECM.

P1262

159

ON

Injector Positive
Voltage Control
Circuit Group 2

• DTC P0612 is not

set.

• The ignition switch is

ON.

• The battery voltage

is more than 18
volts.

• The engine is

running.

Either of following
condition is met:

• The ECM detects

that the common 2
fuel injector drive
circuit is open circuit,
shorted to ground or
shorted to voltage
during engine
rotations.

• The ECM detects

that the cylinder
number 2 or number
3 fuel injector
solenoid coil control
circuit is shorted to
ground during
engine rotations.

• Cylinder #2 or #3 fuel

injector solenoid coil
control circuit is short to
ground.

• Common 2 fuel injector

drive circuit is short to
battery, ignition voltage,
short to ground, open
circuit or high resistance.

• Faulty fuel injector.
• Faulty ECM.

DTC

Flash
Code

MIL

Status

DTC Name

Condition for Running

the DTC

Condition for Setting the

DTC

Possible Cause