Isuzu KB P190. Manual — part 278

6E-78 Engine Control System (4JH1)

DTC P0105 (Symptom Code 2) (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. The vacuum pressure sensor provides
a signal to the ECM on the vacuum pressure signal
circuit which is relative to the vacuum pressure changes
in the turbocharger wastegate valve control hose. The
ECM should detect a low signal voltage at a high
vacuum pressure and high signal voltage at a low
vacuum pressure. The ECM monitors the vacuum
pressure sensor signal for voltage outside the normal
range of the vacuum pressure sensor. If the ECM
detects an excessively low vacuum pressure sensor
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 vacuum pressure

sensor signal voltage is less than 0.5 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 limits fuel injection quantity.
• The ECM uses a barometric pressure of 615 hPa

for turbocharger wastegate valve 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.

Test Description
The number below refers to the step number on the
diagnostic table.
4. If the vacuum pressure sensor signal circuit between
the ECM and the sensor is normal, the sensor signal
voltage high DTC P0105 (Symptom Code 1) will set.

DTC P0105 (Symptom Code 2) (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. Connect a DMM between the 5 volts reference

circuit of the vacuum pressure sensor harness
(pin 3 of C-124 connector) and a known good
ground.

4. Turn ON the ignition, with the engine OFF.
Is the DMM voltage more than the specified value?

4.5 volts

Go to Step 4

Go to Step 5

Engine Control System (4JH1) 6E-79

Step Action

Value(s)

Yes

No

4

1. Turn OFF the ignition.
2. Connect a 3-amp fused jumper wire between the

5 volts reference circuit and the signal circuit of
the vacuum pressure sensor harness (pins 1 and
3 of C-124 connector).

3. Turn ON the ignition, with the engine OFF.
4. Monitor the DTC Information with the scan tool.
Does DTC P0105 (Symptom Code 1) set, but not
DTC P0105 (Symptom Code 2)?



Go to Step 7

Go to Step 6

5

1. Test the 5 volts reference circuit between the

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

• An open circuit
• A short to ground
• A short to the low reference circuit
• High

resistance

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



Go to Step 11

Go to Step 8

6

1. Test the signal circuit between the ECM (pin 85

of C-57 connector) and the vacuum pressure
sensor (pin 1 of C-124 connector) for the
following conditions:

• An open circuit
• A short to ground
• A short to the low reference circuit
• High

resistance

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



Go to Step 11

Go to Step 8

7

1. Turn OFF the ignition.
2. Inspect for an intermittent and for poor

connections at the harness connector of the
vacuum pressure sensor (pins 1 and 3 of C-124
connector).

3. Repair the connection(s) as necessary.
Did you find and correct the condition?



Go to Step 11

Go to Step 9

8

1. Turn OFF the ignition.
2. Disconnect the ECM harness connector.
3. Inspect for an intermittent and for poor

connections on the vacuum pressure sensor
circuits at the harness connector of the ECM
(pins 82 and 85 of C-57 connector).

4. Repair the connection(s) as necessary.
Did you find and correct the condition?



Go to Step 11

Go to Step 10

9

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



Go to Step 11



10

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 11



6E-80 Engine Control System (4JH1)

Step Action

Value(s)

Yes

No

11

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 12

12

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-81

DTC P0105 (Symptom Code 7) (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 high
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 more
than 5.2 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.

DTC P0105 (Symptom Code 7) (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. 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 a short to battery or
ignition voltage.

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



Go to Step 5

Go to Step 4

4

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 5



5

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 6