Isuzu KB P190. Manual — part 281

6E-90 Engine Control System (4JH1)

DTC P0115 (Symptom Code 1) (Flash Code 14)

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 high ECT 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 ECT sensor signal

voltage is more than 4.7 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 uses an ECT substitution of fuel

temperature for engine control.

• The ECM uses an ECT substitution of 60°C

(120

°F) for injection timing control.

• The ECM uses an ECT substitution of -15°C (5°F)

for glow 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.

• After starting the engine, the ECT should rise

steadily to about 80°C – 85°C (176°F – 185°F)
then stabilize when the thermostat opens.

• 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 P0115 (Symptom Code 1) (Flash Code 14)
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 ON the ignition, with the engine OFF.
3. Observe the Engine Coolant Temperature (ECT)

parameter with the scan tool.

Is the ECT parameter less than the specified value?

-35°C (-31°F)

Go to Step 3

Go to Diagnostic

Aids

3

1. Turn OFF the ignition.
2. Disconnect the ECT sensor harness connector.
3. Connect a DMM between the signal circuit of the

ECT sensor harness (pin 1 of E-41 connector)
and a known good ground.

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

5.5 volts

Go to Step 4

Go to Step 5

4

Important: The ECT sensor may be damaged if the
sensor signal circuit is shorted to a voltage source.
1. Test the signal circuit between the engine control

module (ECM) (pin 89 of C-57 connector) and
the ECT sensor (pin 1 of E-41 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 14

Go to Step 13

Engine Control System (4JH1) 6E-91

Step Action

Value(s)

Yes No

5

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

signal circuit and the low reference circuit of the
ECT sensor harness (pins 1 and 2 of E-41
connector).

3. Turn ON the ignition, with the engine OFF.
4. Observe the ECT parameter with the scan tool.
Is the ECT parameter more than the specified
value?

135°C (275°F)

Go to Step 9

Go to Step 6

6

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

signal circuit of the ECT sensor harness (pin 1 of
E-41 connector) and a known good ground.

3. Turn ON the ignition, with the engine OFF.
4. Observe the ECT parameter with the scan tool.
Is the ECT parameter more than the specified
value?

135°C (275°F)

Go to Step 8

Go to Step 7

7

1. Test the signal circuit between the ECM (pin 89

of C-57 connector) and the ECT sensor (pin 1 of
E-41 connector) for an open circuit or high
resistance.

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



Go to Step 14

Go to Step 11

8

1. Test the low reference circuit between the ECM

(pin 93 of C-57 connector) and the ECT sensor
(pin 2 of E-41 connector) for an open circuit or
high resistance.

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



Go to Step 14

Go to Step 11

9

1. Test the signal circuit between the ECM (pin 89

of C-57 connector) and the ECT sensor (pin 1 of
E-41 connector) for a short to any 5 volts
reference circuit.

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



Go to Step 14

Go to Step 10

10

Turn OFF the ignition.
Inspect for an intermittent and for poor connections
at the harness connector of the ECT sensor (pins 1
and 2 of E-41 connector).
Repair the connection(s) as necessary.
Did you find and correct the condition?



Go to Step 14

Go to Step 12

11

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

connections on the ECT sensor circuits at the
harness connector of the ECM (pins 89 and 93 of
C-57 connector).

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



Go to Step 14

Go to Step 13

12

Replace the ECT sensor. Refer to Engine Coolant
Temperature Sensor Replacement in this section.
Did you complete the replacement?



Go to Step 14



13

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 14



6E-92 Engine Control System (4JH1)

Step Action

Value(s)

Yes No

14

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 2

Go to Step 15

15

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-93

DTC P0115 (Symptom Code 2) (Flash Code 14)

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

• The ignition switch is ON.

Condition for Setting the DTC

• The ECM detects that the ECT sensor signal

voltage is less than 0.3 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 uses an ECT substitution of fuel

temperature for engine control.

• The ECM uses an ECT substitution of 60°C

(120

°F) for injection timing control.

• The ECM uses an ECT substitution -15°C (5°F) for

glow 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.

• After starting the engine, the ECT should rise

steadily to about 80°C – 85°C (176°F – 185°F)
then stabilize when the thermostat opens.

• 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 P0115 (Symptom Code 2) (Flash Code 14)
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 ON the ignition, with the engine OFF.
3. Observe the Engine Coolant Temperature (ECT)

parameter with the scan tool.

Is the ECT parameter more than the specified

value?

135°C (275°F)

Go to Step 3

Go to Diagnostic

Aids

3

1. Turn OFF the ignition.
2. Disconnect the ECT sensor harness connector.
3. Turn ON the ignition, with the engine OFF.
4. Observe the Coolant Temperature parameter

with the scan tool.

Is the ECT parameter less than the specified value?

-35°C (-31°F)

Go to Step 5

Go to Step 4

4

1. Test the signal circuit between the engine control

module (ECM) (pin 89 of C-57 connector) and
the ECT sensor (pin 1 of E-41 connector) for the
following conditions:

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

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



Go to Step 8

Go to Step 6