Isuzu N-Series. Manual - part 670

6E-102 Engine Control System (4HK1)

P0090 (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 engine control module (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 solenoid
feedback current, this DTC will set.

Condition for Running the DTC

• DTC P1630 is not set.
• The ignition switch is ON.
• The ignition voltage is more than 18 volts.
• The FRP regulator command duty cycle is

between 10 – 90%.

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

• The ECM detects that the FRP regulator solenoid

feedback current is less than 50 mA.

• The ECM detects that the FRP regulator solenoid

feedback current is more than 2400 mA.

• The ECM detects that the difference of

commanded FRP regulator solenoid current and
feedback current is more than 1000 mA.

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.

• A history DTC clears after 20 consecutive driving

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

Diagnostic Aid

• If an intermittent condition is suspected, refer to

Intermittent Conditions in this section.

Test Description
The numbers below refers to the step number on the
diagnostic table.
7. If the FRP regulator high control circuits between the
ECM and the FRP regulator are shorted to voltage,
engine stalls and will not start.
8. If the FRP regulator low control circuits between the
ECM and the FRP regulator are shorted to ground, this
DTC may not set. This condition will cause engine stall
or no engine start.

DTC P0090 (Flash Code 247)
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.

Turn ON the ignition, with the engine OFF.

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

Does the DTC fail this ignition?

—

Go to Step 3

Go to Diagnostic

Aids

Turn ON the ignition, with the engine OFF.

Observe the Fuel Rail Pressure (FRP)
Regulator Feedback parameter with the Tech
2.

Is the FRP Regulator Feedback parameter more
than the specified value?

300 mA

Go to Step 4

Go to Step 5

Is the FRP Regulator Feedback parameter more
than the specified value at Step 3?

900 mA

Go to Step 7

Go to Step 8

Engine Control System (4HK1) 6E-103

Turn ON the ignition, with the engine OFF.

Disconnect the FRP regulator harness
connector.

Connect a test lamp between the FRP
regulator high control circuit (pin 1 of E-116
connector) and a known good ground.

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

Does the test lamp illuminate?

—

Go to Step 6

Go to Step 9

Turn OFF the ignition.

Connect a test lamp between the FRP
regulator low control circuit (pin 2 of E-116
connector) and battery voltage.

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

Does the test lamp illuminate?

—

Go to Step 11

Go to Step 10

Test the FRP regulator high control circuits
between the engine control module (ECM)
(pins 105 and 113 of E-111 connector) and the
FRP regulator (pin 1 of E-116 connector) for a
short to battery or ignition voltage.

Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 15

Go to Step 14

Test the FRP regulator low control circuits
between the ECM (pins 89 and 97 of E-111
connector) and the FRP regulator (pin 2 of E-
116 connector) for a short to ground.

Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 15

Go to Step 14

Test the FRP regulator high control circuits
between the ECM (pins 105 and 113 of E-111
connector) and the FRP regulator (pin 1 of E-
116 connector) for the following conditions:

• An open circuit
• A short to ground
• A short to the low control circuits
• High resistance

Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 15

Go to Step 12

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

Test the FRP regulator low control circuits
between the ECM (pins 89 and 97 of E-111
connector) and the FRP regulator (pin 2 of E-
116 connector) 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 15

Go to Step 12

Step

Action

Value(s)

Yes

6E-104 Engine Control System (4HK1)

Turn OFF the ignition.

Disconnect the FRP regulator harness
connector.

Inspect for an intermittent and for poor
connections at the FRP regulator harness
connector.

Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 15

Go to Step 13

Turn OFF the ignition.

Disconnect the ECM harness connector.

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

Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 15

Go to Step 14

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

Replace the fuel supply pump. Refer to Fuel Supply
Pump Replacement in this section. (FRP regulator
is part of the fuel supply pump assembly)

Did you complete the replacement?

—

Go to Step 15

—

Important:
Replacement ECM must be programmed.

Replace the ECM. Refer to Engine Control Module
(ECM) Replacement / Fuel Injector ID Code Data
Programming in this section.

Did you complete the replacement?

—

Go to Step 15

—

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 3

Go to Step 16

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-105

P0107 (Flash Code 71)

Circuit Description
The barometric pressure (BARO) sensor is located
under the instrument panel cluster (IPC) near the pedal
bracket. The BARO sensor is a transducer that varies
voltage according to the barometric pressure changes
and the generated voltage is input to the engine control
module (ECM) for the BARO signal. The BARO sensor
has the following circuits.

• 5 volts reference circuit.
• Low reference circuit.
• BARO sensor signal circuit.

The ECM supplies 5 volts to the BARO sensor on the 5
volts reference circuit. The ECM also provides a ground
on the low reference circuit. The BARO sensor
provides a signal to the ECM on the BARO signal
circuit, which is relative to the pressure changes
barometric pressure. The ECM should detect a low
signal voltage at a low barometric pressure, such as
high altitude place. The ECM should detect high signal
voltage at a high barometric pressure. The ECM uses
this voltage signal to calibrate the fuel injection quantity
and injection timing for altitude compensation. If the
ECM detects an excessively low BARO sensor signal
voltage, this DTC will set.

Condition for Running the DTC

• DTCs P1630 and P1632 are not set.
• The ignition switch is ON.
• The ignition voltage is more than 18 volts.

Condition for Setting the DTC

• The ECM detects that the BARO sensor signal

voltage is less than 0.5 volts for 10 seconds.

Action Taken When the DTC Sets

• The ECM illuminates the malfunction indicator

lamp (MIL) when the diagnostic runs and fails.

• The ECM uses a BARO substitution of 75 kPa (11

psi) for engine control.

• The ECM inhibits EGR valve control.

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.

• A history DTC clears after 20 consecutive driving

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

Diagnostic Aid

• If an intermittent condition is suspected, refer to

Intermittent Conditions in this section.

DTC P0107 (Flash Code 71)
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.

Turn ON the ignition, with the engine OFF.

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

Is DTC P1632 also set?

—

Go to DTC P1632

Go to Step 3

Turn ON the ignition, with the engine OFF.

Observe the Barometric Pressure (BARO)
Sensor parameter with the Tech 2.

Is the BARO Sensor parameter less than the
specified value?

0.5 volts

Go to Step 4

Go to Diagnostic

Aids

Turn OFF the ignition.

Disconnect the BARO sensor harness
connector.

Connect a DMM between the 5 volts reference
circuit of the BARO sensor harness (pin 3 of
B-422 connector) and a known good ground.

Turn ON the ignition, with the engine OFF.

Is the DMM voltage more than the specified value?

4.5 volts

Go to Step 5

Go to Step 6

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