Isuzu KB P190. Manual - part 426

ENGINE CONTROL SYSTEM (4JK1/4JJ1) 6E-87

DTC P0091 or P0092 (Flash Code 247)

Circuit Description

The fuel rail pressure (FRP) regulator is installed to the
fuel supply pump and controls the suction fuel quantity
into the fuel rail. The FRP regulator is fully opened in
the normal state and larger drive current results in
smaller opening. The ECM calculates desired fuel rail
pressure and fuel flow rate and it compares the
calculated desired fuel rail pressure to the actual value
to determine the FRP regulator position. When the
actual fuel rail pressure is higher than the desired
value, the FRP regulator is closed to decease the flow
rate. If the ECM detects an excessively low or high FRP
regulator feedback current, DTC P0091 or P0092 will
set.

Condition for Running the DTC

• The battery voltage is more than 9 volts.

• The ignition switch is ON.

Condition for Setting the DTC

• The ECM detects that the FRP regulator feedback

current is less than 100mA, or more than 1000mA
below the desired current. (DTC P0091)

• The ECM detects that the FRP regulator feedback

current is more than 2450mA, or more than
1000mA over the desired current. (DTC P0092)

Action Taken When the DTC Sets

• 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.

Condition for Clearing the DTC

• Refer to DTC Type Definitions for Condition for

Clearing the MIL/ DTC - Type A.

Diagnostic Aids

• If an intermittent condition is suspected, refer to

Intermittent Conditions in this section.

Test Description

The number below refers to the step number on the
Circuit/ System Testing.
8. If the FRP regulator high side circuit is shorted to
voltage, engine stalls and will not start.
9. If the FRP regulator low side circuit is shorted to
ground, this DTC may not set. This will cause engine
stall or no engine start.

Schematic Reference: Engine Controls Schematics

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

Circuit/ System Testing DTC P0091 or P0092

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 a scan tool.

Turn OFF the ignition for 30 seconds.

Turn ON the ignition, with the engine OFF.

Monitor the DTC Information with a scan tool.

Does the DTC fail this ignition?

—

Go to Step 3

Go to Diagnostic

Aids

Is DTC P1064 also set?

—

Go to DTC P1064

Go to Step 4

Observe the Fuel Rail Pressure (FRP) Regulator
Feedback parameter with a scan tool.

Does the scan tool indicate more than the specified
value?

300 mA

Go to Step 5

Go to Step 6

Does the scan tool indicate more than the specified
value at Step 4?

1300 mA

Go to Step 8

Go to Step 9

6E-88 ENGINE CONTROL SYSTEM (4JK1/4JJ1)

Turn OFF the ignition for 30 seconds.

Disconnect the FRP regulator harness
connector.

Connect a test lamp between the high side
circuit (pin 1 of E-50) and a known good
ground.

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

Does the test lamp illuminate then go out?

—

Go to Step 7

Go to Step 10

Turn OFF the ignition for 30 seconds.

Connect a test lamp between the low side
circuit (pin 2 of E-50) and battery voltage.

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

Does the test lamp illuminate then go out?

—

Go to Step 12

Go to Step 11

Test the high side circuits between the ECM
(pins 34 and 54 of E-90) and the FRP
regulator (pin 1 of E-50) for a short to battery
or ignition voltage.

Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 16

Go to Step 15

Test the low side circuits between the ECM
(pins 50 and 70 of E-90) and the FRP
regulator (pin 2 of E-50) for a short to ground.

Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 16

Go to Step 15

Test the high side circuits between the ECM
(pins 34 and 54 of E-90) and the FRP
regulator (pin 1 of E-50) for the following
conditions:

• An open circuit

• A short to ground

• A short to the low side circuit

• High resistance

Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 16

Go to Step 13

Important: The ECM may be damaged if the FRP
regulator low side circuit is shorted to a voltage
source.

Test the low side circuits between the ECM
(pins 50 and 70 of E-90) and the FRP
regulator (pin 2 of E-50) for the following
conditions:

• An open circuit

• A short to battery or ignition voltage

• High resistance

Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 16

Go to Step 13

Step

Action

Value(s)

Yes

ENGINE CONTROL SYSTEM (4JK1/4JJ1) 6E-89

Inspect for an intermittent and for poor
connections at the harness connector of the
FRP regulator (pins 1 and 2 of E-50).

Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 16

Go to Step 14

Turn OFF the ignition.

Disconnect the ECM harness connector.

Inspect for an intermittent and for poor
connections at the harness connector of the
ECM (pins 34, 50, 54 and 70 of E-90).

Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 16

Go to Step 15

Replace the FRP regulator. Refer to Fuel Pump
Replacement.

Did you complete the replacement?

—

Go to Step 16

—

Important: Replacement ECM must be
programmed and learned.
Replace the ECM. Refer to ECM Replacement.

Did you complete the replacement?

—

Go to Step 16

—

Reconnect all previously disconnected
harness connector(s).

Clear the DTCs with a scan tool.

Turn OFF the ignition for 30 seconds.

Start the engine.

Operate the vehicle within the Conditions for
Running the DTC. You may also operate the
vehicle within the conditions that you
observed from the Freeze Frame/ Failure
Records.

Did the DTC fail this ignition?

—

Go to Step 3

Go to Step 17

Observe the DTC Information with a scan tool.

Are there any DTCs that you have not diagnosed?

—

Go to DTC List

System OK

Step

Action

Value(s)

Yes

6E-90 ENGINE CONTROL SYSTEM (4JK1/4JJ1)

DTC P0093 (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 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 fuel rail pressure is certain pressure
low as compared with the engine speed, this DTC will
set.

Condition for Running the DTC

• DTC P0087, P0091, P0092, 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 engine is running.

Condition for Setting the DTC

• The ECM detects that the actual fuel rail pressure

is lower than 15 MPa (2,180 psi) for longer than 5
seconds.

Action Taken When the DTC Sets

• 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.

Condition for Clearing the DTC

• Refer to DTC Type Definitions for Condition for

Clearing the MIL/ DTC - Type A.

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.

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 P0093

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

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