Isuzu N-Series. Manual - part 757

Engine Control System (4JH1) 6E-79

P0115 (Symptom Code 2) (Flash Code 14)

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 excessively low ECT signal voltage, this DTC will
set.

Condition for Running the DTC

• The ignition switch is ON.

Condition for Setting the DTC

• The ECM detects that the ECT sensor signal

voltage is less than 0.3 volts for 3 seconds.

Action Taken When the DTC Sets

• The ECM illuminates the malfunction indicator

lamp (MIL) when the diagnostic runs and fails.

• The ECM uses an ECT substitution of fuel

temperature for engine control.

• The ECM uses an ECT substitution of 60

°C

(120

°F) for injection timing control.

• The ECM uses an ECT substitution of -25

°C (-

°F) for glow control.

Condition for Clearing the MIL/DTC

• The ECM turns OFF the MIL when the diagnostic

runs and does not fail.

• A history DTC clears after 40 consecutive driving

cycles without a fault. Or clear with the Tech 2.

Diagnostic Aids

• 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.

DTC P0115 (Symptom Code 2) (Flash Code 14)
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 ON the ignition, with the engine OFF.

Observe the Engine Coolant Temperature
(ECT) parameter with the Tech 2.

Is the ECT parameter more than the specified
value?

135

°C (275°F)

Go to Step 3

Go to Diagnostic

Aids

Turn OFF the ignition.

Disconnect the ECT sensor harness
connector.

Turn ON the ignition, with the engine OFF.

Observe the Coolant Temperature parameter
with the Tech 2.

Is the ECT parameter less than the specified
value?

-35

°C (-31°F)

Go to Step 5

Go to Step 4

6E-80 Engine Control System (4JH1)

Test the signal circuit between the engine
control module (ECM) (pin 89 of B-233
connector) and the ECT sensor (pin 1 of E-16
connector) for the following conditions:

• A short to ground
• A short to the low reference circuit

Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 8

Go to Step 6

Replace the ECT sensor. Refer to Engine Coolant
Temperature Sensor Replacement in this section.

Did you complete the replacement?

—

Go to Step 8

—

Turn OFF the ignition.

Disconnect the ECM harness connector.

Inspect connections on the ECT sensor
circuits at the harness connector of the ECM
(pins 89 and 93 of B-233 connector) for
corrosion.

Repair or clean the connection(s) as
necessary.

Did you find and correct the condition?

—

Go to Step 8

Go to Step 7

Important:
Replacement ECM must be programmed.

Replace the ECM. Refer to Engine Control Module
(ECM) Replacement in this section.

Did you complete the replacement?

—

Go to Step 8

—

Reconnect all previously disconnected
harness connector(s).

Clear the DTCs with the Tech 2.

Turn OFF the ignition for 30 seconds.

Start the engine.

Monitor the DTC Information with the Tech 2.

Did the DTC fail this ignition?

—

Go to Step 2

Go to Step 9

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 (4JH1) 6E-81

P0180 (Symptom Code B) (Flash Code 15)

Circuit Description
The fuel temperature (FT) sensor is internal to the fuel
injection pump control unit (PCU). It detects fuel
temperature in the fuel injection pump. The engine
control module (ECM) and PCU communicates with
each other over the controller area network (CAN) link.
If the PCU internal FT sensor output is an excessively
high or low, this DTC will set.

Condition for Running the DTC

• The ignition switch is ON.

Condition for Setting the DTC

• The PCU internal FT sensor output is lower than -

°C (-40°F) for 3 seconds or higher than 150°C

(302

°F).

Action Taken When the DTC Sets

• The ECM illuminates the malfunction indicator

lamp (MIL) when the diagnostic runs and fails.

• The ECM uses a default FT substitution for engine

control.

Condition for Clearing the MIL/DTC

• The ECM turns OFF the MIL when the diagnostic

runs and does not fail.

• A history DTC clears after 40 consecutive driving

cycles without a fault. Or clear with the Tech 2.

Diagnostic Aids

• If an intermittent condition is suspected, refer to

Intermittent Conditions in this section.

Notice:

• FT sensor is internal to the PCU and it is part of the

fuel injection pump assembly.

DTC P0180 (Symptom Code B) (Flash Code 15)

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.

Does the DTC fail this ignition?

—

Go to Step 3

Go to Step 4

Important:
The fuel injection pump must be timed to the
engine.

Replace the fuel injection pump. Refer to Fuel
Injection Pump Replacement in engine mechanical
section. (Fuel temperature (FT) sensor is internal
to the fuel injection pump control unit (PCU) and it
is part of the fuel injection pump assembly.)

Did you complete the replacement?

—

Go to Step 4

—

Clear the DTCs with the Tech 2.

Turn OFF the ignition for 30 seconds.

Start the engine.

Monitor the DTC Information with the Tech 2.

Did the DTC fail this ignition?

—

Go to Step 3

Go to Step 5

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

6E-82 Engine Control System (4JH1)

P0215 (Symptom Code A) (Flash Code 52)

Circuit Description
The engine control module (ECM) calculates the
desired fuel injection quantity and timing using data
sent from various sensors. These desired data are
sent to the fuel injection pump control unit (PCU) via a
controller area network (CAN) communication bus.
The PCU also receives signals from the internal inputs:
pump camshaft position (CMP) sensor that is located
inside the fuel injection pump to determine the cam ring
rotation angle and the fuel injection pump speed. The
fuel temperature (FT) sensor is internal the PCU.
These values are used to compare the desired values
sent from the ECM then PCU determines the injection
timer piston position and fuel injection quantity, and
actuates timing control valve (TCV) & fuel injection
solenoid valve based on control maps in the PCU.
The fuel injection solenoid valve is installed to the fuel
injection pump rear side. The fuel injection event is
determined by this solenoid ON/OFF command. The
fuel injection solenoid valve cuts the fuel when the
engine shutoff (ESO) solenoid valve is commanded
shutoff from the PCU. (The fuel injection solenoid
valve and engine shutoff (ESO) solenoid valve is same
part. It calls ESO solenoid valve when fuel is shutoff.)
When the ignition switch is turned OFF or commanded
from fail-safe action, the ESO solenoid valve is
commanded shutoff to stop the engine running. If the
ECM detects that the engine is continuously run after
the ignition switch is OFF, this DTC will set.

Condition for Running the DTC

• The ignition switch is OFF.

• The engine speed is lower than 1500 RPM.
• The vehicle speed is lower than 1.5 km/h (1MPH).

Condition for Setting the DTC

• After the condition for running this DTC for 2

seconds, the engine speed is higher than 200
RPM when the ESO solenoid valve is commanded
shutoff from the PCU. This indicates the PCU
reacts to the command from the ECM but ESO
solenoid valve does not react to the command
from the PCU and fuel cannot shutoff.

Action Taken When the DTC Sets

• The ECM illuminates the malfunction indicator

lamp (MIL) at next ignition cycle.

• The ECM cuts fuel injection.

Condition for Clearing the MIL/DTC

• The ECM turns OFF the MIL when the diagnostic

runs and does not fail.

• A history DTC clears after 40 consecutive driving

cycles without a fault. Or clear with the Tech 2.

Diagnostic Aids

• If an intermittent condition is suspected, refer to

Intermittent Conditions in this section.

Notice:

• Fuel injection solenoid valve is internal to the fuel

injection pump assembly.

• PCU is part of the fuel injection pump assembly.

DTC P0215 (Symptom Code A) (Flash Code 52)

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 and let idle for 30 seconds.

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

Turn OFF the engine.

Does the DTC fail this ignition before the engine
control module (ECM) turned OFF?

—

Go to Step 3

Go to Step 4

Important:
The fuel injection pump must be timed to the
engine.

Replace the fuel injection pump. Refer to Fuel
Injection Pump Replacement in engine mechanical
section.

Did you complete the replacement?

—

Go to Step 4

—

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