Isuzu N-Series. Service manual - part 672

6E-110 Engine Control System (4HK1)

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 13

—

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 2

Go to Step 14

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-111

P0112 (Flash Code 22)

Circuit Description
The intake air temperature (IAT) sensor is fitted
between the air cleaner and turbocharger. The IAT
sensor is a variable resistor. The IAT sensor has a
signal circuit and a low reference circuit. The IAT
sensor measures the temperature of the air entering
the engine. The engine control module (ECM) supplies
5 volts to the IAT signal circuit and a ground for the IAT
low reference circuit. When the IAT sensor is cold, the
sensor resistance is high. When the air temperature
increases, the sensor resistance decreases. With high
sensor resistance, the ECM detects a high voltage on
the IAT signal circuit. With lower sensor resistance, the
ECM detects a lower voltage on the IAT signal circuit. If
the ECM detects an excessively low IAT 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 IAT sensor signal

voltage is less than 0.1 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 an IAT substitution of -10

°C (14°F)

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.

• Use the Temperature vs. Resistance table to test

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

DTC P0112 (Flash Code 22)
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.

Observe the Intake Air Temperature (IAT)
Sensor parameter with the Tech 2.

Is the IAT Sensor parameter less than the specified
value?

0.1 volts

Go to Step 3

Go to Diagnostic

Aids

Turn OFF the ignition.

Disconnect the IAT sensor harness connector.

Turn ON the ignition, with the engine OFF.

Observe the IAT Sensor parameter with the
Tech 2.

Is the IAT Sensor parameter more than the
specified value?

4.8 volts

Go to Step 5

Go to Step 4

6E-112 Engine Control System (4HK1)

Test the signal circuit between the engine
control module (ECM) (pin 72 of J-191
connector) and the IAT sensor (pin 1 of J-190
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 IAT sensor. Refer to Intake Air
Temperature (IAT) 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 IAT sensor circuits
at the harness connector of the ECM (pins 60
and 72 of J-191 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 / Fuel Injector ID Code Data
Programming 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.

Operate the vehicle within the Conditions for
Running the DTC.

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 (4HK1) 6E-113

P0113 (Flash Code 22)

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.
• The engine run time is longer than 3 minutes.

Condition for Setting the DTC

• The ECM detects that the IAT sensor signal

voltage is more than 4.8 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 an IAT substitution of -10

°C (14°F)

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.

• Use the Temperature vs. Resistance table to test

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

DTC P0113 (Flash Code 22)
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.

Observe the Intake Air Temperature (IAT)
Sensor parameter with the Tech 2.

Is the IAT Sensor parameter more than the
specified value?

4.8 volts

Go to Step 3

Go to Diagnostic

Aids

Turn OFF the ignition.

Disconnect the IAT sensor harness connector.

Connect a DMM between the signal circuit of
the IAT sensor harness (pin 1 of J-190
connector) and a known good ground.

Turn ON the ignition, with the engine OFF.

Is the DMM voltage more than the specified value?

5.5 volts

Go to Step 4

Go to Step 5

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