Isuzu KB P190. Manual — part 287

6E-114 Engine Control System (4JH1)

DTC P0243 (Symptom Code 5) (Flash Code 64)

Circuit Description
The engine control module (ECM) controls the
turbocharger wastegate valve based on the barometric
pressure in order to reduce turbocharger spinning
speeds at high altitude area. The ECM controls the
turbocharger wastegate valve diaphragm by acting the
regulated vacuum pressure via controlling the solenoid
valve. The vacuum pressure sensor monitors the
regulated vacuum pressure to the turbocharger
wastegate valve. The ECM calculates desired vacuum
pressure and it compares the calculated desired
vacuum pressure to the actual value to determine the
solenoid valve position. When the actual vacuum
pressure is higher than the desired value, the solenoid
valve is closed to decrease the vacuum pressure. An
expected vacuum pressure amount should be detected
while the engine running. If the ECM detects the actual
vacuum pressure amount is lower than desired vacuum
pressure amount, this DTC will set.
Condition for Running the DTC

• The ignition switch is ON.
• The barometric pressure (BARO) is between 0

hPa and 3500 hPa.

• The intake air temperature (IAT) is between -50°C

(-58 °F) and 200°C (392°F).

• The engine coolant temperature (ECT) is between

-50°C (-58 °F) and 150°C (302°F)

Condition for Setting the DTC

• The ECM detects that the vacuum pressure is 50

hPa lower than the desired vacuum pressure for 3
seconds. This indicates excessive low vacuum
pressure.

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 an EGR solenoid valve control

substitution of 10%.

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.

• Misrouted vacuum hoses may set this DTC.
• A vacuum pump problem will cause this DTC.

Test Description
The numbers below refer to the step number on the
diagnostic table.
4. A skewed vacuum pressure sensor value (shifted to
a low pressure) can set this DTC. The Vacuum
Pressure on the scan tool should read near doubled
barometric pressure (BARO) with the key ON and
engine OFF.
5. A skewed BARO sensor value (shifted to a higher
pressure) may set this DTC. The BARO on the scan
tool should read near surrounding barometric pressure.

DTC P0243 (Symptom Code 5) (Flash Code 64)
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 and let idle for 30 seconds.
4. Monitor the Diagnostic Trouble Code (DTC)

Information with the scan tool.

Is DTC P0105 (Symptom Code 1, 2, 7 or 9) or
P0243 (Symptom Code 4 or 8) set?



Go to Applicable

DTC

Go to Step 3

Engine Control System (4JH1) 6E-115

Step Action

Value(s)

Yes

No

3

1. Turn OFF the ignition.
2. Inspect for the following conditions:

• Vacuum hoses are damaged or kinked.
• Misrouted vacuum hoses.
• A turbocharger solenoid valve is damaged.
• A vacuum pump is damaged.
• A vacuum regulating valve is damaged.
• A turbocharger wastegate valve is

damaged.

• Contaminated, skewed or slow vacuum

pressure sensor.

3. Repair or replace as necessary.
Did you find and correct the condition?



Go to Step 15

Go to Step 4

4

1. Turn ON the ignition, with the engine OFF.
2. Observe the Vacuum Pressure Sensor and

Barometric Pressure (BARO) with the scan tool.

Does the scan tool indicate that the difference
between the Vacuum Pressure Sensor and doubled
BARO is less than the specified value?

10 hPa

Go to Step 7

Go to Step 5

5

1. Observe the BARO parameter with the scan tool.
2. Compare the BARO value to the range specified

in the altitude vs. barometric pressure table.
Refer to Altitude vs. Barometric Pressure.

Is the BARO parameter within the range specified?



Go to Step 6

Go to Step 14

6

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

connector.

3. Inspect for an intermittent and for a poor

connection at the vacuum pressure sensor
harness connector (pin 2 of C-124 connector).

4. Disconnect the engine control module (ECM)

harness connector.

5. Inspect for an intermittent, for a poor connection

and corrosion on vacuum pressure sensor circuit
at the harness connector of the ECM (pin 93 of
C-57 connector).

6. Test for high resistance on vacuum pressure

sensor low reference circuit.

7. Repair the connection(s) or circuit(s) as

necessary.

Did you find and correct the condition?



Go to Step 15

Go to Step 10

7

1. Turn OFF the ignition.
2. Disconnect the vacuum hose from the

turbocharger wastegate valve that is connected
to the vacuum pressure sensor and the
turbocharger solenoid valve.

3. Start the engine and accelerate the engine as

necessary.

Is there boost pressure leak from the turbocharger
wastegate valve port?



Go to Step 13

Go to Step 8

6E-116 Engine Control System (4JH1)

Step Action

Value(s)

Yes

No

8

1. Turn OFF the ignition.
2. Reconnect the vacuum hose to the turbocharger

wastegate valve.

3. Disconnect the vacuum hose from the

turbocharger solenoid valve that is connected to
the vacuum regulating valve “Z” port.

4. Connect a hand-held vacuum pump (5-8840-

0279-0/J-23738-A) to the disconnected vacuum
hose.

5. Start the engine and let engine idle.
Does the hand-held vacuum pump indicate more
than 23 cmHg (9 inHg)?



Go to Step 9

Go to Step 12

9

1. Turn OFF the ignition.
2. Disconnect the hand-held vacuum pump from the

vacuum hose.

3. Reconnect the vacuum hose to the turbocharger

solenoid valve.

4. Disconnect the vacuum hose from the vacuum

pressure sensor that is connected to the
turbocharger solenoid valve and the turbocharger
wastegate valve.

5. Connect a hand-held vacuum pump (5-8840-

0279-0/J-23738-A) to the disconnected vacuum
hose.

6. Disconnect the vacuum pressure sensor harness

connector in order to active turbocharger
solenoid valve.

7 Start the engine and let engine idle.
Does the needle of hand-held vacuum pump shake
between 0 and 20 cmHg (8 inHg)?



Go to Step 10

Go to Step 11

10

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



Go to Step 15



11

Replace the turbocharger solenoid valve. Refer to
Turbocharger Solenoid Valve Replacement in this
section.
Did you complete the replacement?



Go to Step 15



12

Replace the vacuum regulating valve.
Did you compete the replacement?



Go to Step 15



13

Replace the turbocharger wastegate valve. Refer to
Turbocharger in Engine Mechanical section.
Did you complete the replacement?



Go to Step 15



14

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 15



15

1. Reconnect all previously disconnected hoses or

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 2

Go to Step 16

Engine Control System (4JH1) 6E-117

Step Action

Value(s)

Yes

No

16

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