Isuzu D-Max / Isuzu Rodeo (TFR/TFS). Manual - part 221

ENGINE DRIVEABILITY AND EMISSIONS

6E–125

6

Using the DVM and check the IAT sensor.

1. Ignition “Off”,  engine “Off”. 

2. Disconnect IAT sensor connector. 

3. Measure the resistance of IAT sensor. 

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

Standard 

resistance

Go to Step 7

Go to Step 12

7

Using the DVM and check the IAT sensor signal
circuit.

1. Ignition “On”, engine “Off”. 

2. Disconnect the IAT 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

8

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

—

Verify repair

Go to Step 14

9

Repair the short to voltage circuit between the ECM
and IAT sensor. 
Was the problem solved?

—

Verify repair

Go to Step 14

Step

Action

Value(s)

Yes

No

Temperature (°C)

Resistance (

Ω) (Approximately)

-20

32040

0

9788

20

3516

40

1439

60

656

80

327

100

175

IAT Sensor

1

1

2

2

V

C121

1

C56(J2)

C121

1

22

C56(J2)

C121

1

22

6E–126

ENGINE DRIVEABILITY AND EMISSIONS

10

Using the DVM and check the IAT sensor ground
circuit.

1. Ignition “On”, engine “Off”. 

2. Disconnect the IAT sensor connector. 

3. Check the circuit for short to power supply circuit. 

Was the DVM indicated specified value?

Less than 1V

Go to Step 11

Repair faulty 

harness and 

verify repair

11

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

1. Ignition “Off”, engine “Off”. 

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

disconnected) Ref. 6E-80.

3. Disconnect the IAT sensor connector. 

4. Check the circuit for open circuit. 

Was the problem found?

Breaker box is not available: 

1. Ignition “Off”, engine “Off”. 

2. Disconnect the IAT sensor connector. 

3. Check the circuit for open circuit. 

Was the problem found?

—

Repair faulty 

harness and 

verify repair

Go to Step 14

12

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

—

Go to Step 13

Go to Step 14

13

Replace the IAT sensor assembly. 
Is the action complete?

—

Verify repair

—

14

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 15

Step

Action

Value(s)

Yes

No

V

C121

2

33

C121

2

C56(J2)

C121

2

1

ENGINE DRIVEABILITY AND EMISSIONS

6E–127

15

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

No

6E–128

ENGINE DRIVEABILITY AND EMISSIONS

DIAGNOSTIC TROUBLE CODE (DTC) P0117 ENGINE COOLANT 

TEMPERATURE SENSOR LOW INPUT

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

Circuit Description

The engine coolant temperature (ECT) sensor is a
thermistor mounted in the engine coolant stream. The
engine control module (ECM) applies a voltage (about 5
volts) through a pull-up resistor to the ECT signal circuit.
When the engine coolant is cold, the sensor (thermistor)
resistance is high, therefore the ECM will measure a
high signal voltage. As the engine coolant warms, the
sensor resistance becomes lower, and the ECT signal
voltage measured at the ECM drops. Diagnostic Trouble
code P0117 set when the ECM detects an excessively
low signal voltage on the engine coolant temperature
sensor signal circuit.

Diagnostic Aids

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, short to ground, short to battery positive,
and open circuit. If the harness appears to be OK,
observe the ECT display on the Tech 2 while moving
connectors and wiring harnesses related to the ECT
sensor. A change in the ECT display will indicate the
location of the fault.

Code

Type

DTC Name

DTC Setting Condition

Fail-Safe (Back Up)

P0117

A

Engine Coolant Temperature Sensor 
Low Input

1. Engine run time is longer than 120 sec-

onds. 

2. ECT sensor output is more than 149°C. 

The ECM uses default engine coolant 
temperature value based on intake air 
temperature and engine run time. 

µP

0.5
GRY

J1-27

+5V

µP

µP

5Volts
Reference

Knock
Sensor

0.5
YEL

0.5
WHT/
BLU

J1-7

0.5
BLU/
PNK

J1-32

0.5
BLK/
YEL

J1-15

J1-3

Engine
Coolant
Temperature(ECT)
                   Sensor

Throttle
Position Sensor

Knock Filter
Module

Engine
Control
Module
(ECM)