Isuzu N-Series. Manual - part 783

Engine Control System (4JH1) 6E-183

Test the engine cooling system for the
following condition. Refer to diagnosis of the
engine cooling system section for testing.

• Engine coolant level
• Engine coolant leakage
• Cooling fan belt slippage
• Cooling fan clutch working
• Thermostat working
• Water pump working
• Radiator clogging

Repair or replace as necessary.

Did you find and correct the condition?

—

Go to Step 6

Go to Diagnostic

Aids

Reconnect all previously disconnected
harness connector(s).

Clear the DTCs with the Tech 2.

Turn OFF the ignition for 30 seconds.

Start the engine and wait until engine is fully
warms upped.

Observe the ECT parameter with the Tech 2.

Is the ECT parameter more than the specified
value?

100

°C (212°F)

Go to Step 4

Go to Step 7

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

6E-184 Engine Control System (4JH1)

P1173 (Symptom Code 7, A) (Flash Code 22)

Circuit Description
The fuel temperature (FT) sensor is internal to the fuel
injection pump control unit (PCU). It detects fuel
temperature in the fuel injection pump. If the PCU
detects an excessively high or low fuel temperature,
this DTC will set.

Condition for Running the DTC

• The ignition switch is ON.

Condition for Setting the DTC

• The ECM detects an excessive high FT for longer

than 30 seconds. (Symptom Code 7)

• The ECM detects an excessive low FT for longer

than 30 seconds. (Symptom Code A)

Action Taken When the DTC Sets

• The ECM does not illuminate the malfunction

indicator lamp (MIL) when the diagnostic runs and
fails.

• The PCU limits fuel injection quantity. (Symptom

Code 7)

Condition for Clearing the DTC

• A history DTC clears after 40 consecutive driving

cycles without a fault. Or clear with the Tech 2.

Diagnostic Aids

• If an intermittent condition is suspected, refer to

Intermittent Conditions in this section.

Notice:

• FT sensor is internal to the PCU and it is part of the

fuel injection pump assembly.

DTC P1173 (Symptom Code 7, A) (Flash Code 22)

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.

Start the engine.

Monitor the Diagnostic Trouble Code (DTC)
Information with the Tech 2.

Does the DTC fail this ignition?

—

Go to Step 3

Go to Step 4

Important:
The fuel injection pump must be timed to the
engine.

Replace the fuel injection pump. Refer to Fuel
Injection Pump Replacement in engine mechanical
section. (Fuel temperature [FT] sensor is internal
to the fuel injection pump control unit [PCU] and it
is part of the fuel injection pump assembly.)

Did you complete the replacement?

—

Go to Step 4

—

Clear the DTCs with the Tech 2.

Turn OFF the ignition for 30 seconds.

Start the engine.

Monitor the DTC Information with the Tech 2.

Did the DTC fail this ignition?

—

Go to Step 3

Go to Step 5

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

Engine Control System (4JH1) 6E-185

P1335 (Symptom Code A) (Flash Code 43)

Circuit Description
The crankshaft position (CKP) sensor is located on top
of the flywheel housing. There are 4 slits spaced 90

on the flywheel circumference. The CKP sensor is a
magnetic coil type sensor, which generates an AC
signal voltage based on the crankshaft rotational
speed. The engine control module (ECM) monitors
both the CKP sensor and injection pump camshaft
position (CMP) sensor signals to ensure they correlate
with each other. If the fuel injection pump control unit
(PCU) receives faulty CKP sensor signal pulses, this
DTC will set.

Condition for Running the DTC

• The ignition switch is ON.

Condition for Setting the DTC

• The PCU detects CKP sensor signal from the ECM

is faulty.

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 Tech 2.

Diagnostic Aids

• If an intermittent condition is suspected, refer to

Intermittent Conditions in this section.

Notice:

• PCU is part of the fuel injection pump assembly.

DTC P1335 (Symptom Code A) (Flash Code 43)
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.

Start the engine (Note a slight start delay may
be noticed).

Monitor the Diagnostic Trouble Code (DTC)
Information with the Tech 2.

Is DTC P0335 (Symptom Code B or D) set?

—

Go to Applicable

DTC

Go to Step 3

Turn OFF the ignition.

Disconnect the engine control module (ECM)
B-233 harness connector. Keep the B-234
harness connector with connected.

Connect a DMM between the crankshaft
position (CKP) sensor signal output circuit (pin
91 of B-233 connector) and a known good
ground.

Turn ON the ignition, with the engine OFF.

Does the DMM voltage more than the specified
value?

10 volts

Go to Step 5

Go to Step 4

6E-186 Engine Control System (4JH1)

Test the CKP sensor signal output circuit
between the ECM (pin 91 of B-233 connector)
and the fuel injection pump (pin 8 of E-110
connector) for the following conditions:

• An open circuit
• A short to ground
• High resistance

Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 10

Go to Step 6

Test the CKP sensor signal output circuit
between the ECM (pin 91 of B-233 connector)
and the fuel injection pump control unit (PCU)
(pin 8 of E-110 connector) for a short to
battery or ignition voltage.

Notice:
Perform this by connecting a test lamp between the
ECM harness connector (pin 91 of B-233
connector) and a known good ground. If the test
lamp illuminates, circuit is short to battery or
ignition voltage.

Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 10

Go to Step 7

Turn OFF the ignition.

Disconnect the PCU harness connector.

Inspect for an intermittent and for a poor
connection on the CKP sensor signal circuit at
the harness connector of the PCU (pin 8 of E-
110 connector).

Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 10

Go to Step 8

Turn OFF the ignition.

Disconnect the ECM harness connector.

Inspect for an intermittent and for a poor
connection on the CKP sensor signal output
circuit at the harness connector of the ECM
(pin 92 of B-233 connector).

Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 10

Go to Step 9

Important:
The fuel injection pump must be timed to the
engine.

Replace the fuel injection pump. Refer to Fuel
Injection Pump Replacement in engine mechanical
section.

Did you complete the replacement?

—

Go to Step 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 10

—

Step

Action

Value(s)

Yes

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