Content .. 667 668 669 670 ..

Isuzu N-Series. Manual - part 669

6E-98 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

—

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-99

P0089 (Flash Code 151)

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 fuel pressure is a certain
pressure higher than the desired fuel pressure for a
certain length of time, this DTC will set.

Condition for Running the DTC

• DTCs P0090, P0192, P0193, P0201 – P0204,

P0611, P0612, 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 FRP regulator command is more than 40% or

commanded fuel supply is less than a
predetermined value.

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

• The ECM detects that the deferential fuel rail

pressure is higher than 20 MPa (2,900 psi) for
longer than 10 seconds when the engine speed is
between 0 – 600 RPM.

• The ECM detects that the differential fuel rail

pressure is higher than 40 MPa (5,800 psi) for
longer than 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 high 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.

• A skewed FRP sensor value (shifted to a higher

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.

DTC P0089 (Flash Code 151)
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

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,
P1261 or P1262 set?

—

Go to Applicable

DTC

Go to Step 3

6E-100 Engine Control System (4HK1)

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 Fuel Rail Pressure (FRP) Sensor
parameter with the Tech 2.

Is the FRP Sensor parameter the specified value?

0.9 – 1.0 volt

Go to Step 4

Go to Step 5

Turn OFF the ignition.

Disconnect the FRP regulator harness
connector.

Inspect for an intermittent, for poor
connections and corrosion at the harness
connector of the FRP regulator (pins 1 and 2
of E-116).

Disconnect the engine control module (ECM)
harness connector.

Inspect for an intermittent, for poor
connections and corrosion on each FRP
regulator circuit at the harness connector of
the ECM (pins 89, 97, 105 and 113 of E-111
connector).

Test for high resistance on each FRP regulator
circuit.

Repair the connection(s) or circuit(s) as
necessary.

Did you find and correct the condition?

—

Go to Step 10

Go to Step 6

Turn OFF the ignition.

Disconnect the FRP sensor harness
connector.

Inspect for an intermittent, for poor
connections and corrosion at the harness
connector of the FRP sensor (pins 1, 2 and 3
of E-113 connector).

Disconnect the ECM harness connector.

Inspect for an intermittent, for poor
connections and corrosion on each FRP
sensor circuit at the harness connector of the
ECM (pins 82, 87, 90 and 101 of E-111
connector).

Test for high resistance on each FRP circuit.

Repair the connection(s) or circuit(s) as
necessary.

Did you find and correct the condition?

—

Go to Step 10

Go to Step 8

Turn OFF the ignition for 30 seconds.

Place the transmission in Neutral and set the
Park brake.

Start the engine.

Let the engine idle with the engine coolant
temperature between 60 – 85

°C (140 – 185°F)

and accessories OFF while observing the
Differential Fuel Rail Pressure parameter with
the Tech 2.

Is the Differential Fuel Rail Pressures parameter
with the specified value?

± 5 MPa (± 725

psi)

Go to Step 7

Go to Step 9

Step

Action

Value(s)

Yes

Engine Control System (4HK1) 6E-101

Notice:
An intermittent problem by foreign material in the
fuel is suspected.

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

Did you complete the replacement?

—

Go to Step 10

—

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

Did you complete the replacement?

—

Go to Step 10

—

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 10

—

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 11

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

Content .. 667 668 669 670 ..