Content .. 695 696 697 698 ..

Isuzu N-Series. Manual - part 697

6E-210 Engine Control System (4HK1)

Replace the fuel filter cartridge. Refer to Fuel Filter
Cartridge Replacement in the Fuel System Section.

Did you complete the replacement?

—

Go to Step 17

—

Replace the FRP sensor. Refer to Fuel Rail
Pressure (FRP) Sensor Replacement in this
section.

Did you complete the replacement?

—

Go to Step 17

—

Important:
Replacement injector must be programmed.

Replace the appropriate fuel injector that does not
change engine speed when commanded OFF.
Refer to Fuel Injector Replacement / Fuel Injector
ID Code Data Programming in this section.

Did you complete the replacement?

—

Go to Step 17

—

Important:
The fuel supply pump must be timed to the engine
and adjustment value must be learned to the ECM.

Notice:
Always replace the fuel filter cartridge when a fuel
supply pump is replaced.

Replace the fuel supply pump and fuel filter
cartridge. Refer to Fuel Supply Pump Replacement
in this section and Fuel Filter Cartridge
Replacement in Fuel System section.

Did you complete the replacement?

—

Go to Step 17

—

Notice:
There is a possibility that the pressure limiter valve
stuck open or opening pressure has fallen.

Replace the pressure limiter valve. Refer to Fuel
Rail Replacement in this section.

Did you complete the replacement?

—

Go to Step 17

—

Reconnect all previously disconnected
harness connector(s).

Clear the DTCs with the Tech 2.

Turn OFF the ignition for 30 seconds.

Start the engine.

Operate the vehicle within the Conditions for
Running the DTC.

Did the DTC fail this ignition?

—

Go to Step 2

Go to Step 18

Observe the DTC Information with the Tech 2.

Are there any DTCs that you have not diagnosed?

—

Go to Diagnostic

Trouble Code (DTC)

List

System OK

Step

Action

Value(s)

Yes

Engine Control System (4HK1) 6E-211

P1094 (Flash Code 226)

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 differential fuel rail pressure
is small at low engine speed but the FRP regulator
commanded fuel is certain amount high for a certain
length of time, this DTC will set. (FRP Regulator
Command High DTC)
If the ECM detects that the fuel rail pressure sensor
signal voltage is certain amount low for a certain length
of time when fuel cut, DTC will also set. (FRP Drop
DTC)

Condition for Running the DTC
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.

Condition for Setting the DTC
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.

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.

6E-212 Engine Control System (4HK1)

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 P1094 (Flash Code 226)
Schematic Reference: Engine Controls Schematics
Connector End View Reference: Engine Controls
Connector End Views or Engine Control Module (ECM)
Connector End Views

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

Engine Control System (4HK1) 6E-213

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

Turn OFF the ignition.

Wait 2 minutes for the fuel pressure to bleed
down from the fuel rail.

Turn ON the ignition with the engine OFF. DO
NOT start the engine.

Observe the FRP Sensor parameter with the
Tech 2.

Is the FRP Sensor parameter the specified value?

0.9 – 1.0 volt

Go to Step 6

Go to Step 13

Step

Action

Value(s)

Yes

Content .. 695 696 697 698 ..