Isuzu N-Series. Manual - part 681

6E-146 Engine Control System (4HK1)

Test the CKP sensor circuits between the
ECM (pins 106 and 107 of E-111 connector)
and CKP sensor (pins 1 and 2 of E-98
connector) for the following conditions:

• A short to battery or ignition voltage
• A short to any 5 volts reference

Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 17

Go to Step 16

Turn OFF the ignition.

Inspect for an intermittent and for poor
connections at the harness connector of the
CKP sensor (pins 1 and 2 of E-98 connector).

Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 17

Go to Step 16

Turn OFF the ignition.

Disconnect the ECM harness connector.

Inspect for an intermittent and for poor
connections on the CKP sensor circuits at the
harness connector of the ECM (pins 106 and
107 of E-111 connector).

Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 17

Go to Step 16

Replace the CKP sensor. Refer to Crankshaft
Position (CKP) Sensor Replacement in this section.

Did you complete the replacement?

—

Go to Step 17

—

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 17

—

Reconnect all previously disconnected
harness connector(s).

Clear the DTCs with the Tech 2.

Turn OFF the ignition for 30 seconds.

Start the engine.

Accelerate the Accelerate the engine between
idle and W.O.T. (accelerator pedal full travel)
many times while observing the Engine Speed
parameter with Tech 2.

Does the Engine Speed parameter ever exceed the
specified value?

3700 RPM

Go to Step 4

Go to Step 18

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-147

P0234 (Flash Code 42)

Circuit Description
The boost pressure sensor is located in the air
induction tubing. The sensor is a transducer that varies
voltage according to changes in the air pressure inside
the air tubing. The engine control module (ECM)
monitors the boost pressure sensor signal for abnormal
values. If the ECM detects that the boost pressure
sensor signal is excessively high, this DTC will set.

Condition for Running the DTC

• DTCs P0237, P0238, P1630 and P1634 are not

set.

• The ignition switch is ON.
• The ignition voltage is more than 18 volts.
• The engine is running.
• The fuel injection quantity is lower than a

predetermined value.

Condition for Setting the DTC

• The ECM detects that the boost pressure is higher

than 228 kPa (33 psi) for 3 seconds.

Action Taken When the DTC Sets

• The ECM illuminates the malfunction indicator

lamp (MIL) when the diagnostic runs and fails.

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

• An open circuit or high resistance in the boost

pressure low reference circuit may set this DTC.

• Check the turbocharger wastegate valve for a

sticking or close stuck condition.

• Use the Tech 2 to verify the integrity of the boost

pressure sensor signal. Compare the sensor
values under all load conditions for an excessively
high value. Use the Tech 2 data list values for
nominal sensor readings.

• The fuel with which gasoline was mixed may set

this DTC.

Test Description
The numbers below refer to the step number on the
diagnostic table.
2. A skewed boost pressure sensor value (shifted to a
higher pressure) can set this DTC. The Boost Pressure
on the Tech 2 should read near Barometric Pressure
(BARO) with the key ON and engine OFF.
3. A skewed BARO sensor value (shifted to a lower
pressure) may indicate a wrong boost pressure sensor
reading. The BARO on the Tech 2 should read near
surrounding barometric pressure.

DTC P0234 (Flash Code 42)
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 Boost Pressure and Barometric
Pressure (BARO) with the Tech 2.

Does the Tech 2 indicate that the difference
between the Boost Pressure and BARO is more
than the specified value?

7.0 kPa (1.0

psi)

Go to Step 3

Go to Step 4

Observe the BARO parameter with the Tech 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 5

Go to Step 8

6E-148 Engine Control System (4HK1)

Inspect the following for possible causes of
high boost pressure.

• Wastegate for a stuck closed condition.

Refer to the Turbocharger in Engine
Mechanical section for diagnosis.

• Oil in the air induction tubing causing an

incorrect boost pressure sensor signal.
When there is adhesion of oil inside of
the tubing, intercooler or turbocharger it
needs to be wiped off.

Repair the condition as necessary.

Did you find and correction the condition?

—

Go to Step 11

Go to Diagnostic

Aids

Turn OFF the ignition.

Disconnect the boost pressure sensor
harness connector.

Inspect for an intermittent and for a poor
connection at the boost pressure sensor
harness connector (pin 1 of J-216 connector).

Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 11

Go to Step 6

Turn ON the ignition, with the engine OFF.

Connect a test lamp between the boost
pressure sensor low reference circuit (pin 1 of
J-216 connector) and battery voltage.

Does the test lamp illuminate?

—

Go to Step 9

Go to Step 7

Repair the high resistance in low reference circuit
between the engine control module (ECM) (pin 109
of E-111 connector) and boost pressure sensor (pin
1 of J-216 connector).

Did you complete the repair?

—

Go to Step 11

—

Turn OFF the ignition.

Disconnect the BARO sensor harness
connector.

Inspect for an intermittent and for poor
connections at the BARO sensor harness
connector (pins 2 and 3 of B-422 connector).

Disconnect the ECM harness connector.

Inspect for an intermittent, for poor
connections and corrosion on each BARO
sensor circuit at the harness connector of the
ECM (pins 61 and 71 of J-191 connector).

Test for high resistance on each BARO sensor
circuit.

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

Did you find and correct the condition?

—

Go to Step 11

Go to Step 10

Replace the boost pressure sensor. Refer to Boost
Pressure Sensor Replacement in this section.

Did you complete the replacement?

—

Go to Step 11

—

Replace the BARO sensor. Refer to Barometric
Pressure (BARO) Sensor Replacement in this
section.

Did you complete the replacement?

—

Go to Step 11

—

Step

Action

Value(s)

Yes

Engine Control System (4HK1) 6E-149

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 12

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

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