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Isuzu D-Max / Isuzu Rodeo (TFR/TFS). Manual - part 32

4JA1-TC/4JH1-TC ENGINE DRIVEABILITY AND EMISSIONS

6E–123

Using the DVM and check the IAT sensor signal
circuit.
Breaker box is available:

1. Ignition “Off”, engine “Off”.

2. Install the breaker box as type A. (ECM

disconnected) Ref. Page 6E-81

3. Disconnect the MAF & IAT sensor connector.

4. Check the circuit for short to sensor ground or

ground circuit.

Was the problem found?

Breaker box is not available:

1. Ignition “Off”, engine “Off”.

2. Disconnect the MAF & IAT sensor connector and

ECM connector.

3. Check the circuit for short to sensor ground or

ground circuit.

Was the problem found?

—

Repair faulty
harness and

verify repair

Go to Step 10

Substitute a known good MAF & IAT sensor assembly
and recheck.
Was the problem solved?

—

Go to Step 9

Go to Step 10

Replace the MAF & IAT sensor assembly.
Is the action complete?

—

Verify repair

—

Is the ECM programmed with the latest software
release?
If not, download the latest software to the ECM using
the “SPS (Service Programming System)”.
Was the problem solved?

—

Verify repair

Go to Step 11

Replace the ECM.
Is the action complete?
IMPORTANT: The replacement ECM must be
programmed. Refer to section of the Service
Programming System (SPS) in this manual.
Following ECM programming, the immobiliser system
(if equipped) must be linked to the ECM. Refer to
section 11 “Immobiliser System-ECM replacement” for
the ECM/Immobiliser linking procedure.

—

Verify repair

—

Step

Action

Value(s)

Yes

C-57(B)

6E–124

4JA1-TC/4JH1-TC ENGINE DRIVEABILITY AND EMISSIONS

DIAGNOSTIC TROUBLE CODE (DTC) P0115 (SYMPTOM CODE 1)

(FLASH CODE 14) ENGINE COOLANT TEMPERATURE SENSOR CIRCUIT HIGH

INPUT

DIAGNOSTIC TROUBLE CODE (DTC) P0115 (SYMPTOM CODE 2)

(FLASH CODE 14) ENGINE COOLANT TEMPERATURE SENSOR CIRCUIT LOW

INPUT

Condition for setting the DTC and action taken when the DTC sets

Circuit Description

The ECT sensor is a thermistor. A temperature changes
the resistance value. And it changes voltage. In other
words it measures a temperature value. It is installed on

the coolant stream. Low coolant temperature produces
a high resistance.
The ECM supplies 5 volts signal to the ECT sensor
through resisters in the ECM and measures the voltage.
The signal voltage will be high when the engine

Flash

Code

Symptom

Code

MIL

DTC Name

DTC Setting Condition

Fail-Safe (Back Up)

P0115

Engine Coolant Temperature
(ECT) Sensor Circuit High
Input

ECT sensor output voltage is
more than 4.7V.

1. ECM uses fuel temperature

as substitute.

2. ECM uses 60°C condition for

injection timing control.

3. ECM uses -15°C condition

for glow time control.

Engine Coolant Temperature
(ECT) Sensor Circuit Low
Input

ECT sensor output voltage is
below 0.3V.

0.5
BLK

0.5
GRN/
BLK

0.5
RED/
GRN

0.5
GRN/
ORG

0.5
BLK/
GRN

2.0
BLK

0.5
BLK/
PNK

0.5
GRY

ECT

Sensor

TPS &

Idle SW

0.5
WHT

101

0.5
GRN/
RED

CKP

Sensor

Engine
Control
Module
(ECM)

4JA1-TC/4JH1-TC ENGINE DRIVEABILITY AND EMISSIONS

6E–125

temperature is cold, and it will be low when the engine
temperature is hot.
The output voltage excessively high or low, DTC P0115
(Symptom Code 1) or P0115 (Symptom Code 2) will be
stored.

Diagnostic Aids

An intermittent may be caused by the following:

• Poor connections.

• Misrouted harness.

• Rubbed through wire insulation.

• Broken wire inside the insulation.
Check for the following conditions:

• Poor connection at ECM-Inspect harness connectors

for backed out terminals, improper mating, broken
locks, improperly formed or damaged terminals, and
poor terminal to wire connection.

• Damaged harness-Inspect the wiring harness for

damage. If the harness appears to be OK, observe
the “Coolant Temperature” display on the Tech2 while
moving connectors and wiring harness related to the
sensor.

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

Engine Coolant Temperature Sensor Circuit High Input

Step

Action

Value(s)

Yes

Was the “On-Board Diagnostic (OBD) System Check”
performed?

—

Go to Step 2

Go to On Board

Diagnostic

(OBD) System

Check

1. Connect the Tech 2.

2. Review and record the failure information.

3. Select “F0: Read DTC Infor As Stored By ECU” in

“F0: Diagnostic Trouble Codes”.

Is the DTC P0115 (Symptom Code 1) stored as
“Present Failure”?

—

Go to Step 3

Refer to

Diagnostic Aids

and Go to Step

1. Using the Tech 2, ignition “On” and engine “Off”.

2. Select “F1: Clear DTC Information” in “F0:

Diagnostic Trouble Codes” with the Tech 2 and
clear the DTC information.

3. Operate the vehicle and monitor the “F0: Read

DTC Infor As Stored By ECU” in the “F0:
Diagnostic Trouble Codes”.

Was the DTC P0115 (Symptom Code 1) stored in this
ignition cycle?

—

Go to Step 4

Refer to

Diagnostic Aids

and Go to Step

Check for poor/faulty connection at the ECT sensor or
ECM connector. If a poor/faulty connection is found,
repair as necessary.
Was the problem found?

—

Verify repair

Go to Step 5

Visually check the ECT sensor.
Was the problem found?

—

Go to Step 12

Go to Step 6

E-41

C-57(B)

6E–126

4JA1-TC/4JH1-TC ENGINE DRIVEABILITY AND EMISSIONS

Using the DVM and check the ECT sensor.

1. Ignition “Off”, engine “Off”.

2. Disconnect ECT sensor connector.

3. Measure the resistance of ECT sensor.

Does the tester indicate standard resistance as shown
in the following table?

Standard

resistance

Go to Step 7

Go to Step 12

Using the DVM and check the ECT sensor signal
circuit.

1. Ignition “On”, engine “Off”.

2. Disconnect the ECT sensor connector.

3. Check the circuit for open circuit.

Was the DVM indicated specified value?

Approximately

5.0V

Go to Step 10

Less than 1V:

Go to Step 8

More than

specified value:

Go to Step 9

Repair the open circuit between the ECM and ECT
sensor.
Was the problem solved?

—

Verify repair

Go to Step 14

Step

Action

Value(s)

Yes

Temperature (°C)

Resistance (

Ω) (Approximately)

-30

27500

-20

16100

5760

2370

1080

537

290

100

161

120

ECT Sensor

E-41

C-57(B)

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