Isuzu N-Series. Manual - part 700

6E-222    Engine Control System (4HK1) 

13

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

—

14

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

Did you complete the replacement?

—

Go to Step 17

—

15

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

—

16

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

—

17

1.

Reconnect all previously disconnected
harness connector(s).

2.

Clear the DTCs with the Tech 2.

3.

Turn OFF the ignition for 30 seconds.

4.

Start the engine.

5.

Operate the vehicle within the Conditions for
Running the DTC.

Did the DTC fail this ignition?

—

Go to Step 2

Go to Step 18

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

No

 Engine Control System (4HK1)    6E-223

P1173 (Flash Code 542)

Circuit Description
The engine coolant temperature (ECT) sensor is
installed to the thermostat housing. The ECT sensor is
a variable resistor. The ECT sensor has a signal circuit
and a low reference circuit. The ECT sensor measures
the temperature of the engine coolant. The engine
control module (ECM) supplies 5 volts to the ECT
signal circuit and a ground for the ECT low reference
circuit. When the ECT sensor is cold, the sensor
resistance is high. When the engine coolant
temperature increases, the sensor resistance
decreases. With high sensor resistance, the ECM
detects a high voltage on the ECT signal circuit. With
lower sensor resistance, the ECM detects a lower
voltage on the ECT signal circuit. If the ECM detects an
excessive high coolant temperature, this DTC will set.

Condition for Running the DTC

• DTCs P0117, P0118, P1630 and P1634 are not

set.

• The ignition switch is ON.
• The ignition voltage is more than 18 volts.
• The engine is running.

Condition for Setting the DTC

• The ECM detects that the engine coolant

temperature is more than 110

°C (230°F) for 15

seconds.

Action Taken When the DTC Sets

• The ECM does not illuminate the malfunction

indicator lamp (MIL) when the diagnostic runs and
fails.

Condition for Clearing the DTC

• 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.

• After starting the engine, the ECT should rise

steadily to about 80

°C – 85°C (176°F – 185°F)

then stabilize when the thermostat opens.

• Use the Temperature vs. Resistance table to test

the ECT sensor at various temperature levels to
evaluate the possibility of a skewed sensor. A
skewed sensor could result in poor driveability
concerns.

Notice:

• This DTC is caused by an engine overheat

condition (i.e. low engine coolant level). Since this
DTC does not illuminate any lamps, clear the DTC
and ensure there are no signs of engine damage.
Excessive engine overheat may damage internal
engine components.

DTC P1173 (Flash Code 542)

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.

Install the Tech 2.

2.

Turn OFF the ignition for 30 seconds.

3.

Turn ON the ignition, with the engine OFF.

4.

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

Is DTC P0117 also set?

—

Go to DTC P0117

Go to Step 3

3

1.

Start the engine and wait until engine is fully
warms upped.

2.

Observe the Coolant Temperature parameter
with the Tech 2.

Is the Coolant Temperature parameter more than
the specified value?

110

°C (230°F)

Go to Step 5

Go to Step 4

6E-224    Engine Control System (4HK1) 

4

Ask the driver if overheat is caused by low engine
coolant level, etc.
If engine overheat has experienced, the engine
must be inspected and repaired as necessary.

Did you complete the action?

—

Go to Step 7

—

5

1.

Test the engine coolant temperature (ECT)
sensor at various temperature levels to
evaluate the possibility if a skewed sensor.

2.

Replace the ECT sensor as necessary.

Did you find and correct the condition?

—

Go to Step 7

Go to Step 6

6

1.

Test the engine cooling system for the
following condition. Refer to diagnosis of the
engine cooling system section for testing.

• Engine coolant level
• Engine coolant leakage
• Cooling fan belt slippage
• Cooling fan clutch working
• Thermostat working
• Water pump working
• Radiator clogging

2.

Repair or replace as necessary.

Did you find and correct the condition?

—

Go to Step 7

Go to Diagnostic 

Aids

7

1.

Reconnect all previously disconnected
harness connector(s).

2.

Clear the DTCs with the Tech 2.

3.

Turn OFF the ignition for 30 seconds.

4.

Start the engine and wait until engine is fully
warms upped.

5.

Observe the Coolant Temperature parameter
with the Tech 2.

Is the Coolant Temperature parameter more than
the specified value?

110

°C (230°F)

Go to Step 2

Go to Step 8

8

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

No

 Engine Control System (4HK1)    6E-225

P1220 (Flash Code 28)

Circuit Description
The power take off (PTO) throttle sensor (body builder
installed) detects the PTO control throttle angle. The
engine control module (ECM) receives the PTO control
throttle angle from the throttle sensor and controls the
fuel injection quantity (engine speed) during PTO. The
PTO throttle sensor has the following circuits.

• 5 volts reference circuit
• Low reference circuit
• PTO throttle sensor signal circuit

The ECM supplies 5 volts to the PTO throttle sensor on
the 5 volts reference circuit. The ECM also provides a
ground on the low reference circuit. The ECM monitors
the PTO throttle sensor signal for voltages outside the
normal range of the PTO throttle sensor. If the ECM
detects an excessively high PTO throttle sensor signal
voltage, this DTC will set.

Condition for Running the DTC

• DTCs P1630 and P1631 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 PTO throttle sensor

signal voltage is more than 4.8 volts.

Action Taken When the DTC Sets

• The ECM illuminates the malfunction indicator

lamp (MIL) when the diagnostic runs and fails.

• The ECM disables PTO throttle sensor 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.

• PTO throttle sensor may have an intermittent open

somewhere in the operating range.

DTC P1220 (Flash Code 28)
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

No

1

Did you perform the Diagnostic System Check –
Engine Controls?

—

Go to Step 2

Go to Diagnostic 

System Check – 

Engine Controls

2

1.

Install the Tech 2.

2.

Turn OFF the ignition for 30 seconds.

3.

Start the engine.

4.

Observe the PTO Remote Throttle Sensor
parameter with the Tech 2 while turning the
PTO throttle sensor.

Does the PTO Remote Throttle Sensor parameter
ever exceed specified value?

4.8 volts

Go to Step 3

Go to Diagnostic 

Aids

3

1.

Start the engine.

2.

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

Is DTC P1631 also set?

—

Go to Step 4

Go to Step 5

4

1.

Turn OFF the ignition.

2.

Disconnect the PTO throttle sensor harness
connector.

3.

Turn ON the ignition, with the engine OFF.

4.

Observe the PTO Remote Throttle Sensor
parameter with the Tech 2.

Is the PTO Remote Throttle Sensor parameter less
than the specified value?

0.2 volts

Go to DTC P1631

Go to Step 7