Isuzu N-Series. Manual - part 673

6E-114 Engine Control System (4HK1)

Important:
The IAT sensor may be damaged if the sensor
signal circuit is shorted to a voltage source.

Test the signal circuit between the engine
control module (ECM) (pin 72 of J-191
connector) and the IAT sensor (pin 1 of J-190
connector) for a short to battery or ignition
voltage.

Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 14

Go to Step 13

Turn OFF the ignition.

Connect a test lamp between the signal circuit
of the IAT sensor harness (pin 1 of J-190
connector) and a known good ground.

Connect a DMM between the probe of the test
lamp and a known good ground.

Turn ON the ignition, with the engine OFF.

Is the DMM voltage more than the specified value?

4.5 volts

Go to Step 9

Go to Step 6

Turn OFF the ignition.

Connect a 3-amp fused jumper wire between
the signal circuit and low reference circuit of
the IAT sensor harness (pins 1 and 2 of J-190
connector).

Turn ON the ignition, with the engine OFF.

Observe the IAT Sensor parameter with the
Tech 2.

Is the IAT Sensor parameter less than the specified
value?

0.1 volts

Go to Step 10

Go to Step 7

Test the signal circuit between the ECM (pin
72 of J-191 connector) and the IAT sensor (pin
1 of J-190 connector) for an open circuit or
high resistance.

Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 14

Go to Step 8

Test the low reference circuit between the
ECM (pin 60 of J-191 connector) and the IAT
sensor (pin 2 of J-190 connector) for an open
circuit or high resistance.

Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 14

Go to Step 11

Test the signal circuit between the ECM (pin
72 of J-191 connector) and the IAT sensor (pin
1 of J-190 connector) for a short to any 5 volts
reference circuit.

Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 14

Go to Step 13

Turn OFF the ignition.

Inspect for an intermittent and for poor
connections at the harness connector of the
IAT sensor (pins 1 and 2 of J-190 connector).

Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 14

Go to Step 12

Step

Action

Value(s)

Yes

Engine Control System (4HK1) 6E-115

Turn OFF the ignition.

Disconnect the ECM harness connector.

Inspect for an intermittent and for poor
connections on the IAT sensor circuits at the
harness connector of the ECM (pins 60 and
72 of J-191 connector).

Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 14

Go to Step 13

Replace the IAT sensor. Refer to Intake Air
Temperature (IAT) Sensor Replacement in this
section.

Did you complete the replacement?

—

Go to Step 14

—

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 14

—

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 15

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-116 Engine Control System (4HK1)

P0117 (Flash Code 23)

Circuit Description
The engine coolant temperature (ECT) sensor is
installed to the thermostat housing. The ECT sensor is
a variable resistor. The ECT sensor has a signal circuit
and a low reference circuit. The ECT sensor measures
the temperature of the engine coolant. The engine
control module (ECM) supplies 5 volts to the ECT
signal circuit and a ground for the ECT low reference
circuit. When the ECT sensor is cold, the sensor
resistance is high. When the engine coolant
temperature increases, the sensor resistance
decreases. With high sensor resistance, the ECM
detects a high voltage on the ECT signal circuit. With
lower sensor resistance, the ECM detects a lower
voltage on the ECT signal circuit. If the ECM detects an
excessively low ECT signal voltage, this DTC will set.

Condition for Running the DTC

• DTCs P1630 and P1634 are not set.
• The ignition switch is ON.
• The ignition voltage is more than 18 volts.

Condition for Setting the DTC

• The ECM detects that the ECT sensor signal

voltage is less than 0.1 volts for 10 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 ECT substitution of -20

°C (-4°F)

for engine starting control.

• The ECM uses an ECT substitution of 110

°C

(230

°F) for engine control.

• The ECM inhibits EGR valve control.

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

• If an intermittent condition is suspected, refer to

Intermittent Conditions in this section.

• Use the Temperature vs. Resistance table to test

the ECT sensor at various temperature levels to
evaluate the possibility of a skewed sensor. A
skewed sensor could result in poor driveability
concerns.

DTC P0117 (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

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.

Turn ON the ignition, with the engine OFF.

Observe the Coolant Temperature Sensor
parameter with the Tech 2.

Is the Coolant Temperature Sensor parameter less
than the specified value?

0.1 volts

Go to Step 3

Go to Diagnostic

Aids

Turn OFF the ignition.

Disconnect the engine coolant temperature
(ECT) sensor harness connector.

Turn ON the ignition, with the engine OFF.

Observe the Coolant Temperature Sensor
parameter with the Tech 2.

Is the Coolant Temperature Sensor parameter
more than the specified value?

4.8 volts

Go to Step 5

Go to Step 4

Engine Control System (4HK1) 6E-117

Test the signal circuit between the engine
control module (ECM) (pin 84 of E-111
connector) and the ECT sensor (pin 1 of E-90
connector) for the following conditions:

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

Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 8

Go to Step 6

Replace the ECT sensor. Refer to Engine Coolant
Temperature (ECT) Sensor Replacement in this
section.

Did you complete the replacement?

—

Go to Step 8

—

Turn OFF the ignition.

Disconnect the ECM harness connector.

Inspect connections on the ECT sensor
circuits at the harness connector of the ECM
(pins 84 and 109 of E-111 connector) for
corrosion.

Repair or clean the connection(s) as
necessary.

Did you find and correct the condition?

—

Go to Step 8

Go to Step 7

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 8

—

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 9

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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