Isuzu N-Series. Manual — part 749

Engine Control System (4JH1) 6E-47

P0251

(E)

53

ON

Injection Pump
Fuel Metering
Control

• The ignition switch

is ON.

• The ECM detects

communication
message from the
PCU is not
received for longer
than 1 second.

• CAN high circuit is open

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

• CAN low circuit is open

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

• Electrical interference.
• Magnetic interference.
• Faulty PCU.
• Faulty ECM.

P0335

(B)

43

ON

Crankshaft
Position (CKP)
Sensor Circuit

• The ignition switch

is ON.

• The engine speed

is higher than 665
RPM.

• The ECM detects

extra or missing
CKP sensor
signals while
engine is running.

• Sensor signal circuit is

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

• Sensor low reference

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

• Sensor shield ground is

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

• Faulty CKP sensor.
• Faulty ECM.
• Electrical interference.
• Magnetic interference.
• Faulty sensor

installation.

• Faulty flywheel

circumference.

DTC

(Symptom

Code)

Flash
Code

MIL

Status

DTC Name on

Tech 2

Condition for Running

the DTC

Condition for Setting

the DTC

Possible Cause

6E-48 Engine Control System (4JH1)

P0335

(D)

43

ON

Crankshaft
Position (CKP)
Sensor Circuit

• DTC P0335

(Symptom Code B)
is not set.

• The ignition switch

is ON.

• The fuel injection

pump CMP sensor
signal is
generated.

• The CAN

communication
between the ECM
and PCU is
normal.

• The ECM detects

that the CKP
sensor signals are
not generated
when doubled fuel
injection pump
rotation speed is
higher than 50
RPM.

• Sensor signal circuit is

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

• Sensor low reference

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

• Sensor shield ground is

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

• Faulty CKP sensor.
• Faulty ECM.
• Electrical interference.
• Magnetic interference.
• Faulty sensor

installation.

• Faulty flywheel

circumference.

P0335

(E)

43

ON

Crankshaft
Position (CKP)
Sensor Circuit

• The ignition switch

is ON.

• The ECM detects

that the engine
speed is higher
than 5700 RPM for
0.2 seconds.

• Engine overrun.
• Faulty CKP sensor.
• Faulty ECM.
• Electrical interference.
• Magnetic interference.
• Faulty flywheel

circumference.

P0380

(4)

66

ON

Glow Plug
Relay Control
Circuit Low
Voltage

• The ignition switch

is ON.

• The ECM detects

that the low voltage
condition on the
glow relay control
circuit for longer
than 3 seconds
when the relay is
commanded OFF.

• Glow relay ignition

voltage feed circuit on
coil side is open circuit or
high resistance.

• Glow relay control circuit

is open circuit, high
resistance or short to
ground.

• Glow relay is poor

installation.

• Faulty glow relay.
• Faulty ECM.

P0380

(8)

66

ON

Glow Plug
Relay Control
Circuit High
Voltage

• The ignition switch

is ON.

• The ECM detect

that the high
voltage condition
on the glow relay
control circuit for
longer than 1
second when the
relay is
commanded ON.

• Glow relay control circuit

is short to battery or
ignition voltage circuit.

• Faulty glow relay.
• Faulty ECM.

DTC

(Symptom

Code)

Flash
Code

MIL

Status

DTC Name on

Tech 2

Condition for Running

the DTC

Condition for Setting

the DTC

Possible Cause

Engine Control System (4JH1) 6E-49

P0381

(4)

67

ON

Glow Plug
Indicator Circuit
Low Voltage

• The ignition switch

is ON.

• The ECM detects

that the low voltage
condition on the
glow indicator lamp
control circuit for
longer than 3
seconds when the
indicator lamp is
commanded OFF.

• Meter (10A) fuse (F-16)

open.

• Glow indicator lamp

ignition voltage feed
circuit is open circuit or
high resistance.

• Glow indicator lamp

control circuit is open
circuit, high resistance or
short to ground.

• Poor harness connector

connection.

• Glow indicator lamp bulb

burned out.

• Faulty instrument panel

cluster (meter
assembly).

• Faulty ECM.

P0381

(8)

67

ON

Glow Plug
Indicator Circuit
High Voltage

• The ignition switch

is ON.

• The ECM detects

that the high
voltage condition
on the glow
indicator lamp
control circuit for
longer than 1
second when the
indicator lamp is
commanded ON.

• Glow indicator lamp

control circuit is short to
battery or ignition voltage
circuit.

• Faulty instrument panel

cluster (meter
assembly).

• Faulty ECM.

P0400

(3)

32

ON

Exhaust Gas
Recirculation
(EGR) System
Performance

• The ignition switch

is ON.

• The engine is

running.

• The BARO is

between 880 hPa
and 1100 hPa.

• The IAT is between

16

°C (61°F) and

34

°C (93°F).

• The ECT is

between 70

°C

(158

°F) and 100°C

(212

°F).

• The ECM detects

that the MAF
amount is 150 mg/
strk lower than the
desired MAF for 60
seconds.

• MAF sensor circuits are

high resistance.

• MAF sensor signal circuit

is short to IAT sensor
signal circuit.

• Intake air leakage.
• Intake duct

disconnected.

• Intake system is

obstructed.

• Faulty turbocharger.
• Faulty exhaust system.
• Faulty EGR valve

vacuum control system.

• Faulty EGR valve.
• Faulty EGR solenoid

valve.

• Faulty EGR solenoid

valve vacuum hose
routing.

• Faulty MAF sensor.

DTC

(Symptom

Code)

Flash
Code

MIL

Status

DTC Name on

Tech 2

Condition for Running

the DTC

Condition for Setting

the DTC

Possible Cause

6E-50 Engine Control System (4JH1)

P0400

(4)

32

ON

Exhaust Gas
Recirculation
(EGR) Solenoid
Circuit Low
Voltage

• The ignition switch

is ON.

• The ECM detects

that the low voltage
condition on the
EGR solenoid
valve control circuit
for longer than 3
seconds when the
solenoid valve is
commanded OFF.

• EGR solenoid valve

ignition voltage feed
circuit is open circuit or
high resistance.

• EGR solenoid valve

control circuit is open
circuit, high resistance or
short to ground.

• Poor harness connector

connection.

• Faulty EGR solenoid

valve.

• Faulty ECM.

P0400

(5)

32

ON

Exhaust Gas
Recirculation
(EGR) System
Performance

• The ignition switch

is ON.

• The engine is

running.

• The BARO is

between 880 hPa
and 1100 hPa.

• The IAT is between

16

°C (61°F) and

34

°C (93°F).

• The ECT is

between 70

°C

(158

°F) and 100°C

(212

°F).

• The ECM detects

that the MAF
amount is 150 mg/
strk higher than the
desired MAF for 60
seconds.

• MAF sensor low

reference circuit is high
resistance.

• Faulty EGR valve

vacuum control system.

• Faulty EGR valve.
• Faulty vacuum pump.
• Faulty EGR solenoid

valve.

• Faulty EGR solenoid

valve vacuum hose
routing.

• Faulty MAF sensor.
• Faulty ECM.

P0400

(8)

32

ON

Exhaust Gas
Recirculation
(EGR) Solenoid
Circuit High
Voltage

• The ignition switch

is ON.

• The ECM detects

that the high
voltage condition
on the EGR
solenoid valve
control circuit for
longer than 3
seconds when the
solenoid valve is
commanded ON.

• EGR solenoid valve

control circuit is short to
battery or ignition voltage
circuit.

• Faulty EGR solenoid

valve.

• Faulty ECM.

P0500

(1)

24

OFF

Vehicle Speed
Sensor (VSS)
Circuit

• The ignition switch

is ON.

• The ECM detects

that the vehicle
speed is higher
than 190 km/h (119
MPH) for 5
seconds.

• Vehicle speed too high.
• Electrical interference.
• Magnetic interference.
• Faulty VSS.
• Faulty ECM.

P0500

(A)

24

OFF

Vehicle Speed
Sensor (VSS)
Circuit

• The ignition switch

is ON.

• The ECM detects

that the vehicle
speed sensor
signal frequency is
too high for 0.6
seconds.

• Electrical interference.
• Magnetic interference.
• Faulty VSS.
• Faulty ECM.

DTC

(Symptom

Code)

Flash
Code

MIL

Status

DTC Name on

Tech 2

Condition for Running

the DTC

Condition for Setting

the DTC

Possible Cause