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Isuzu N-Series. Manual - part 666

6E-86 Engine Control System (4HK1)

P1635

5V Reference
Circuit 5

• DTC P1630 is not

set.

• The ignition switch is

ON.

• The battery voltage

is between 16 – 32
volts.

Either of following
condition is met:

• The ECM detects

that the 5 volts
reference circuit 2 or
5 voltage is less
than 4.5 volts.

• The ECM detects

that the 5 volts
reference circuit 2 or
5 voltage is more
than 5.5 volts.

• Same as DTC P1632.

P1681

Exhaust Brake
Valve Circuit Low
Voltage

• The ignition switch is

ON.

• The battery voltage

is between 16 – 32
volts.

• The engine is

running.

• The ECM detects a

low voltage
condition on the
exhaust brake
solenoid valve
control circuit for
longer than 10
seconds when the
solenoid valve is
commanded OFF.

• Exhaust brake solenoid

valve voltage feed circuit
is open circuit or high
resistance.

• Exhaust brake solenoid

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

• Poor harness connector

connection.

• Faulty exhaust brake

solenoid valve.

• Faulty ECM.

P1682

Exhaust Brake
Valve Circuit
High Voltage

• The ignition switch is

ON.

• The battery voltage

is between 16 – 32
volts.

• The engine is

running.

• The ECM detects a

high voltage
condition on the
exhaust brake
solenoid valve
control circuit for
longer than 10
seconds when the
solenoid valve is
commanded ON.

• Exhaust brake solenoid

valve control circuit is
short to battery or
ignition voltage.

• Faulty exhaust brake

solenoid valve.

• Faulty ECM.

U2104

CAN Bus Reset
Counter Overrun

• The ignition switch is

ON.

• The ECM detects

that the CAN Bus
OFF status.

• CAN Low circuit is short

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

• CAN High circuit is short

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

• Faulty resistor 1.
• Faulty resistor 2.
• Faulty ECM.
• Faulty DRM.
• Faulty TCM.
• Faulty EHCU.
• Electromagnetic

interference and
electrical noise.

DTC

Flash
Code

MIL

Status

DTC Name

Condition for Running

the DTC

Condition for Setting the

DTC

Possible Cause

Engine Control System (4HK1) 6E-87

U2106

Lost CAN
Communications
With
Transmission
Control System

• The ignition switch is

ON.

• The ECM detects

that the CAN Bus
messages from the
TCM are not being
received.

• CAN Low circuit to the

TCM is open circuit.

• CAN High circuit to the

TCM is open circuit.

• Faulty resistor 1.
• Faulty resistor 2.
• Faulty ECM.
• Faulty TCM.
• Electromagnetic

interference and
electrical noise.

DTC

Flash
Code

MIL

Status

DTC Name

Condition for Running

the DTC

Condition for Setting the

DTC

Possible Cause

6E-88 Engine Control System (4HK1)

P0087 (Flash Code 227)

Description
The common rail fuel system is comprised of two fuel
pressure sections: a suction side between the fuel tank
and the fuel supply pump and a high-pressure side
between the fuel supply pump and the fuel injectors.
Fuel is drawn from the fuel tank via a feed pump and
then pumped into the fuel rail by two plungers, all of
which are internal to the fuel supply pump. This high
pressure is regulated by the engine control module
(ECM) using the fuel rail pressure (FRP) regulator
dependant upon values from the FRP sensor attached
to the fuel rail. In case of fuel rail overpressure, a
pressure limiter valve threaded into the fuel rail will
open to release overpressure and return fuel back to
the fuel tank.
If the ECM detects that the fuel rail pressure is certain
pressure low as compared with engine speed, this DTC
will set.

Condition for Running the 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.

Condition for Setting the DTC
Either of following condition is met:

• The ECM detects that the FRP sensor signal

voltage is 1.0 volt for 10 seconds when the engine
speed is between 0 – 600 RPM.

• The ECM detects that the FRP sensor signal

voltage is less than 1.2 volts for 10 seconds when
the engine speed is higher than 900 RPM.

Action Taken When the DTC Sets

• The ECM illuminates the malfunction indicator

lamp (MIL) when the diagnostic runs and fails.

• The ECM limits accelerator control range.
• The ECM inhibits pilot injection.

Condition for Clearing the MIL / DTC

• The ECM turns OFF the MIL when the key is

cycled after a current DTC clears.

• A current DTC clears when the diagnostic runs and

does not fail at next driving cycle.

• A history DTC clears after 20 consecutive driving

cycles without a fault. Or clear with the Tech 2 or
accelerator pedal operation.

Diagnostic Aid

• An intermittently sticking FRP regulator may have

allowed the fuel pressure to become low enough to
set this DTC.

• Normal FRP Sensor readings on the Tech 2 with

the engine running in neutral at idle is around 1.4 –
1.6 volts.

• An intermittently sticking fuel injector may have

allowed the fuel pressure to drop too much. Use
the Tech 2 to perform the Injector Balancing test
for each injector. Verify a consistent engine speed
change when commanding each fuel injector ON
and OFF.

• A skewed FRP sensor value (shifted to a lower

pressure) can set this DTC. The FRP Sensor on
the Tech 2 should read 0.9 – 1.0 volt with the key
ON and engine OFF after the engine has stopped
running for a minimum of 2 minutes.

Notice:

• This DTC most likely indicates a loss of fuel

pressure by a fuel leak from the high pressure
side. Inspect the high pressure side fuel leakage
between the fuel supply pump and fuel injector
FIRST.

Notice:

• The fuel system from the fuel tank(s) to the fuel

supply pump is under a slight vacuum with the
engine running. As a result, air can enter the fuel
system if these connections are not tight or if there
is a crack in one of the fuel hoses. Air in the fuel
system will cause fuel rail pressure fluctuations
especially at high engine speed and load, which
may set this DTC.

Notice:

• If the fuel tank is empty or near empty, air might be

allowed to go into the fuel system. With air in the
fuel system, smooth flow of fuel into the supply
pump is interrupted and this DTC may set. Perform
bleeding of fuel system after refilling.

Test Description
The numbers below refers to the step number on the
diagnostic table.
7. This step checks for a fuel restriction by determining
if a high vacuum is being pulled on the fuel system
during normal operation.
8. This step checks for an air leak on the suction side of
the fuel system by determining if a vacuum can be
pulled when a fuel line is plugged.

DTC P0087 (Flash Code 227)
Schematic Reference: Engine Controls Schematics
Connector End View Reference: Engine Controls
Connector End Views or Engine Control Module (ECM)
Connector End Views

Engine Control System (4HK1) 6E-89

Step

Action

Value(s)

Yes

Did you perform the Diagnostic System Check –
Engine Controls?

—

Go to Step 2

Go to Diagnostic

System Check –

Engine Controls

Inspect the high pressure side between the
fuel supply pump and the fuel injectors for fuel
leakage. The following components may
contain an external leak.

• Fuel supply pump
• Fuel rail
• Pressure limiter valve
• Flow damper valve
• Fuel rail pressure (FRP) sensor
• Fuel pipe between the fuel supply pump

and fuel rail

• Fuel pipe between the fuel rail and fuel

injectors

• Each fuel pipe sleeve nuts

Notice:
Fuel may leak under the cylinder head cover from
the inlet high pressure line. In such case, the
engine oil level will rise. Inspect for fuel leakage
into the engine oil.

Notice:
Remove and inspect the inlet high pressure joint to
the fuel injectors for fuel leaking from the sleeve
nut(s). Replace the fuel injector and injection pipe
when foreign material was in contact.

Repair any fuel system leaks as necessary.

Did you find and correct the condition?

—

Go to Step 20

Go to Step 3

Remove each glow plug from the cylinder
head.

Inspect the tip of the plugs for wet fuel.

Notice:
Use the engine compression gauge (5-8840-2675-
0 / J-26999-12) and gauge adapter (5-8840-2815-0
/ EN-46722) to inspect the damage of engine. If
poor engine compression (less than 1960 kPa [284
psi]) or variation of each cylinder (more than 294
kPa [43 psi]) is found, inspect the engine
mechanical. Refer to the Engine Mechanical
section. Repair as necessary.

Did you find wet fuel on the glow plug(s)?

—

Go to Step 16

Go to Step 4

Install the Tech 2.

Turn OFF the ignition for 30 seconds.

Start the engine.

Monitor the Diagnostic Trouble Code (DTC)
Information with the Tech 2.

Is DTC P0090, P0192, P0193, P0201 – P0204,
P1094, P1095, P1261 or P1262 set?

—

Go to Applicable

DTC

Go to Step 5

Content .. 664 665 666 667 ..