Isuzu KB P190. Service manual — part 279

6E-82 Engine Control System (4JH1)

Step Action

Value(s)

Yes

No

6

Observe the DTC Information with the scan tool.
Are there any DTCs that you have not diagnosed?



Go to Diagnostic

Trouble Code (DTC)

List System

OK

Engine Control System (4JH1) 6E-83

DTC P0105 (Symptom Code 9) (Flash Code 34)

Circuit Description
The vacuum pressure sensor is installed to the
turbocharger wastegate control hose and it detects the
regulated vacuum pressure to the turbocharger
wastegate valve. The vacuum pressure sensor is a
transducer that varies voltage according to changes in
the vacuum pressure inside the vacuum hose. The
vacuum pressure sensor has the following circuits.

• 5 volts reference circuit
• Low reference circuit
• Vacuum pressure sensor signal circuit

The engine control module (ECM) supplies 5 volts to
the vacuum pressure sensor on the 5 volts reference
circuit. The ECM also provides a ground on the low
reference circuit. If the ECM detects an excessively low
vacuum pressure sensor 5 volts reference 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 vacuum pressure

sensor 5 volts reference circuit voltage is less than
4.5 volts for 2.5 seconds.

Action Taken When the DTC Sets

• The ECM illuminates the malfunction indicator

lamp (MIL) when the diagnostic runs and fails.

• The ECM limits fuel injection quantity.

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 scan tool.

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
diagnostic table.
3. If the vacuum pressure sensor 5 volts reference
circuit between the ECM and the sensor is normal, the
sensor signal voltage low DTC P0105 (Symptom Code
2) will set.

DTC P0105 (Symptom Code 9) (Flash Code 34)
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 scan tool.
2. Turn OFF the ignition for 30 seconds.
3. Start the engine.
4. Monitor the Diagnostic Trouble Code (DTC)

Information with the scan tool.

Does the DTC fail this ignition?



Go to Step 3

Go to Diagnostic

Aids

3

1. Turn OFF the ignition.
2. Disconnect the vacuum pressure sensor harness

connector.

3. Turn ON the ignition, with the engine OFF.
4. Monitor the DTC Information with the scan tool.
Does DTC P0105 (Symptom Code 2) set, but not
DTC P0105 (Symptom Code 9)?



Go to Step 5

Go to Step 4

4

1. Test the 5 volts reference circuit between the

engine control module (ECM) (pin 82 of C-57
connector) and the vacuum pressure sensor (pin
3 of C-124 connector) for the following
conditions:

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

2. Repair the circuit(s) as necessary.
Did you find and correct the condition?



Go to Step 7

Go to Step 6

6E-84 Engine Control System (4JH1)

Step Action

Value(s)

Yes

No

5

Replace the vacuum pressure sensor. Refer to
Vacuum Pressure Sensor Replacement in this
section.
Did you complete the replacement?



Go to Step 7



6

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 7



7

1. Reconnect all previously disconnected harness

connector(s).

2. Clear the DTCs with the scan tool.
3. Turn OFF the ignition for 30 seconds.
4. Start the engine.
5. Monitor the DTC Information with the scan tool.
Did the DTC fail this ignition?



Go to Step 3

Go to Step 8

8

Observe the DTC Information with the scan tool.
Are there any DTCs that you have not diagnosed?



Go to Diagnostic

Trouble Code (DTC)

List System

OK

Engine Control System (4JH1) 6E-85

DTC P0110 (Symptom Code 1) (Flash Code 23)

Circuit Description
The intake air temperature (IAT) sensor is fitted
between the air cleaner and turbocharger internal to the
mass air flow (MAF) sensor. 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 high IAT 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 IAT sensor signal

voltage is more than 4.7 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 IAT substitution of 0°C (32°F)

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 scan tool.

Diagnostic Aids

• 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.

Notice:

• The mass air flow (MAF) sensor is heated and as

a result the IAT sensor may indicate a higher than
normal intake temperature if the ignition switch is
being ON.

DTC P0110 (Symptom Code 1) (Flash Code 23)
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 scan tool.
2. Turn ON the ignition, with the engine OFF.
3. Observe the Intake Air Temperature (IAT)

parameter with the scan tool.

Is the IAT parameter less than the specified value?

-38°C (-36°F)

Go to Step 3

Go to Diagnostic

Aids

3

1. Turn OFF the ignition.
2. Disconnect the mass air flow/intake air

temperature (MAF/IAT) sensor harness
connector.

3. Connect a DMM between the signal circuit of the

IAT sensor harness (pin 1 of C-116 connector)
and a known good ground.

4. 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

4

Important: The IAT sensor may be damaged if the
sensor signal circuit is shorted to a voltage source.
1. Test the signal circuit between the engine control

module (ECM) (pin 84 of C-57 connector) and
the IAT sensor (pin 1 of C-116 connector) for a
short to battery or ignition voltage.

2. Repair the circuit(s) as necessary.
Did you find and correct the condition?



Go to Step 14

Go to Step 13