Isuzu KB P190. Manual - part 462

ENGINE CONTROL SYSTEM (4JK1/4JJ1)   6E-231

DTC 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 ECM using the fuel rail
pressure (FRP) regulator dependant upon values from
the FRP sensor attached to the fuel rail.
If the ECM detects that the difference between the
actual and the desired fuel pressure is small at low
engine speed but the FRP regulator commanded fuel
flow is certain amount high, this DTC will set. (FRP
Regulator Commanded High DTC)
If the ECM detects that the fuel rail pressure is sharply
decreased when fuel cut, this DTC will also set. (Fuel
Pressure Drop DTC)

Condition for Running the DTC

FRP Regulator Commanded High DTC

• DTCs P0087, P0091, P0092, P0117, P0118,

P0182, P0183, P0192, P0193, P0500, P0501,
P0652, P0653, P0201 - P0204, P1064, P1065,
P124B and P2146 - P2151 are not set.

• The battery voltage is more than 9 volts.

• The ignition switch is ON.

• The accelerator pedal is not depressed.

• The engine coolant temperature is more than 50

°C

(122

°F).

• The vehicle speed is less than 3km/h (2MPH).

Fuel Pressure Drop DTC

• DTCs P0087, P0091, P0092, P0182, P0183,

P0192, P0193, P0652, P0653, P0201 - P0204,
P1064, P1065, P124B and P2146 - P2151 are not
set.

• The battery voltage is more than 9 volts.

• The ignition switch is ON.

• The accelerator pedal is not depressed.

• The engine speed is more than 1500RPM.

• The vehicle speed is more than 3km/h (2MPH).

Condition for Setting the DTC

FRP Regulator Commanded High DTC

• The ECM detects that the FRP regulator

commanded fuel flow is more than a
predetermined range for longer than 10 seconds
when the engine speed is near idle speed.

Fuel Pressure Drop DTC

• The ECM detects that the fuel rail pressure is

dropped more than a threshold when the
commanded fuel is cut.

Action Taken When the DTC Sets

FRP Regulator Commanded High DTC

• The ECM illuminates the MIL when the diagnostic

runs and fails. Refer to DTC Type Definitions for
Action Taken When the DTC Sets - Type A.

• The ECM limits fuel injection quantity.

• The ECM inhibits pilot injection.

• The ECM inhibits cruise control.

Fuel Pressure Drop DTC

• The ECM illuminates the SVS lamp when the

diagnostic runs and fails. Refer to DTC Type
Definitions for Action Taken When the DTC Sets -
Type C. (Euro 4 Specification)

• The ECM illuminates the MIL when the diagnostic

runs and fails. Refer to DTC Type Definitions for
Action Taken When the DTC Sets - Type A.
(Except Euro 4 Specification)

• The ECM limits fuel injection quantity.

• The ECM inhibits pilot injection.

• The ECM inhibits cruise control.

• The ECM stops engine running when the vehicle

speed is lower than 5 km/h (3 MPH) for 5 seconds.
The engine will run after the key is cycled when the
ignition has been tuned OFF for longer than 10
seconds.

Condition for Clearing the DTC

FRP Regulator Commanded High DTC

• Refer to DTC Type Definitions for Condition for

Clearing the MIL/ DTC - Type A.

Fuel Pressure Drop DTC

• Refer to DTC Type Definitions for Condition for

Clearing the SVS Lamp/ DTC - Type C. (Euro 4
Specification)

• Refer to DTC Type Definitions for Condition for

Clearing the MIL/ DTC - Type A. (Except Euro 4
Specification)

Diagnostic Aids

• An intermittently sticking FRP regulator may have

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

• Normal Fuel Rail Pressure readings on the scan

tool with the engine running in neutral at idle is
around 27 to 33 MPa (3,900 to 4,800 psi) after
warm up.

• A skewed FRP sensor value can set this DTC. The

FRP Sensor on the scan tool should read 0.9 to
1.0 volt with the key ON and engine OFF after the
engine has stopped running for a minimum of 1
minute.

6E-232   ENGINE CONTROL SYSTEM (4JK1/4JJ1)

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.

• 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.

Schematic Reference: Fuel System Routing Diagram
and Engine Controls Schematics

Connector End View Reference: Engine Controls
Connector End Views or ECM Connector End Views

Circuit/ System Testing DTC P1094

Step

Action

Value(s)

Yes

No

1

Did you perform the Diagnostic System Check -
Engine Controls?

—

Go to Step 2

Go to Diagnostic 

System Check - 
Engine Controls

2

1.

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

• 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.

2.

Repair any fuel system leaks as necessary.

Did you find and correct the condition?

—

Go to Step 19

Go to Step 3

3

1.

Remove each glow plug from the cylinder
head.

2.

Inspect for fuel leakage into the combustion
chamber.

Is there a cylinder that fuel leakage into the
combustion chamber?

—

Go to Step 15

Go to Step 4

4

1.

Install a scan tool.

2.

Turn OFF the ignition for 30 seconds.

3.

Start the engine.

4.

Monitor the DTC Information with a scan tool.

Is DTC P0087, P0091, P0092, P0192, P0193,
P0201 - P0204, P1064, P1065, P124B or P2146 -
P2151 set?

—

Go to Applicable 

DTC

Go to Step 5

ENGINE CONTROL SYSTEM (4JK1/4JJ1)   6E-233

5

1.

Turn OFF the ignition.

2.

Wait 1 minute for the fuel pressure to bleed
down from the fuel rail.

3.

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

4.

Observe the Fuel Rail Pressure (FRP) Sensor
parameter with the scan tool.

Does the scan tool indicate within the specified
value?

0.9 to 1.0 volt

Go to Step 6

Go to Step 13

6

1.

Turn OFF the ignition.

2.

Place the transmission in Neutral and set the
parking brake.

3.

Start the engine and let idle for at least 3
minutes while observing the DTC Information
with a scan tool.

Does the DTC fail this ignition?

—

Go to Step 8

Go to Step 7

7

1.

Accelerate the engine between idle and
W.O.T. (accelerator pedal full travel) many
times.

2.

Let idle for at least 3 minutes while observing
the DTC Information with a scan tool.

Does the DTC fail this ignition?

—

Go to Step 18

Go to Step 8

8

1.

Start the engine.

2.

Perform the Cylinder Balance Test with a scan
tool.

3.

Command each injector OFF and verify an
engine speed change for each injector.

Is there an injector that does not change engine
speed when commanded OFF?

—

Go to Step 16

Go to Step 9

9

1.

Check the fuel system line connections
between the fuel tank and the fuel supply
pump for tightness and all fuel hoses for cuts,
cracks and for the use of proper clamps.

Notice: Air in the fuel system will cause fuel rail
pressure fluctuations especially at high engine
speed and load, which may set this DTC.

2.

Repair or replace as necessary.

Did you find and correct the condition?

—

Go to Step 19

Go to Step 10

Step

Action

Value(s)

Yes

No

6E-234   ENGINE CONTROL SYSTEM (4JK1/4JJ1)

10

Notice: Make sure the in-tank fuel pump operation
before performing the following procedures. Refer
to In-tank Fuel Pump System Check in this section.

1.

Turn OFF the ignition.

2.

Disconnect the fuel hose from the fuel supply
pump suction side. In order to measure the
discharged fuel amount, put the hose into a
bottle or a container with a scale. (The inlet of
a bottle or a container must be larger than the
diameter of hose.)

3.

Turn ON the ignition for 20 seconds, with the
engine OFF.

4.

Turn OFF the ignition for 10 seconds.

5.

Perform 3 and 4 three times. The accumulated
fuel of three ignition cycles must be more than
300 cc. (Normal amount is more than 100 cc
per one ignition cycle.)

Notice: If there is a leak or a restriction on the
suction side, the fuel from the hose will not flow out
sufficiently that is most likely caused by fuel
leakage, clogged fuel filter, kinked or crushed fuel
hose or pipe. Also inside the fuel tank for any
foreign materials may be getting drawn into the fuel
line pickup.

6.

Repair fuel system leaking or restrictions as
necessary.

Did you find and correct the condition?

—

Go to Step 19

Go to Step 11

11

1.

Remove the fuel hose that connects to the fuel
supply pump suction side and substitute a
clear hose.

Notice: The hose must be cleaned before
connecting to the fuel line. Otherwise, foreign
material internal to the hose may damage the fuel
supply pump.

2.

Bleed the fuel system. Repeat as necessary
until the engine starts.

3.

Let the engine run at idle for at least 1 minute.

4.

Observe the clear hose while holding the
engine speed higher than 3000 RPM for a
minimum of 1 minute.

Notice: If many air bubbles appear in the fuel,
check the fuel line connections between the fuel
supply pump and the fuel tank for tightness and all
fuel hoses for cuts, cranks and for the uses of
proper clamps.

5.

Repair or replace as necessary.

Did you find and correct the condition?

—

Go to Step 19

Go to Step 12

Step

Action

Value(s)

Yes

No