Isuzu KB P190. Manual - part 574

6E–126

ENGINE DRIVEABILITY AND EMISSIONS

10

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

1. Ignition “Off”, engine “Off”. 

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

disconnected) Refer to 6E-88 page.

3. Disconnect the MAP 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 MAP sensor connector and ECM

connector. 

3. Check the circuit for open circuit. 

Was the problem found?

—

Repair faulty 

harness and 

verify repair

Go to Step 11

11

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

—

Go to Step 12

Go to Step 13

12

Replace the MAP sensor. 
Is the action complete?

—

Verify repair

—

13

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 14

14

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 immobilizer system
(if equipped) must be linked to the ECM. Refer to
section 11 “Immobilizer System-ECM replacement” for
the ECM/Immobilizer linking procedure.

—

Verify repair

—

Step

Action

Value(s)

Yes

No

J1-16

Breaker Box

Ω

E-85

1

1

16

E85

E60(J1)

ENGINE DRIVEABILITY AND EMISSIONS

6E–127

DIAGNOSTIC TROUBLE CODE (DTC) P0112 INTAKE AIR TEMPERATURE 

SENSOR LOW INPUT

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

Circuit Description

The intake air temperature (IAT) sensor is a thermistor
which measures the temperature of the air entering the
engine. The engine control module (ECM) applies 5
volts through a pull-up resistor to the IAT sensor. When
the intake air is cold, the sensor resistance is high and
the ECM will monitor a high signal voltage on the IAT
signal circuit. If the intake air is warm, the sensor
resistance is lower, causing the ECM to monitor a lower
voltage. Diagnostic Trouble Code P0112 will set when
the ECM detects an excessively low signal voltage

(short to ground) on the intake air 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 and open

Code

Type

DTC Name

DTC Setting Condition

Fail-Safe (Back Up)

P0112

A

Intake Air Temperature Sensor Low 
Input

1. No DTC relating to VSS. 
2. Vehicle speed is more than 25km/h. 
3. Engine run time is longer than 120 sec-

onds. 

4. IAT sensor output is more than 149 deg. C. 

The ECM uses 20 deg. C condition as 
substitute.

6E–128

ENGINE DRIVEABILITY AND EMISSIONS

circuit. If the harness appears to be OK, observe the
IAT display on the Tech 2 while moving connectors
and wiring harnesses related to the IAT sensor. A

change in the IAT display will indicate the location of
the fault.

Diagnostic Trouble Code (DTC) P0112 

Intake Air Temperature Sensor Low Input

Step

Action

Value(s)

Yes

No

1

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

—

Go  to  Step 2

Go to On Board 

Diagnostic 

(OBD) System 

Check

2

1. Connect the Tech 2. 

2. Review and record the failure information. 

3. Select “F0: Read DTC Infor By Priority” in “F0:

Diagnostic Trouble Code”. 

Is the DTC P0112 stored as “Present Failure”?

—

Go to Step 3

Refer to 

Diagnostic Aids 

and Go to Step 

3

3

1. Using the Tech2, ignition “On” and engine “Off”. 

2. Select “Clear DTC Information” with the Tech2 and

clear the DTC information. 

3. Operate the vehicle and monitor the “F5: Failed

This Ignition” in “F2: DTC Information”.

Was the DTC P0112 stored in this ignition cycle?

—

Go to Step 4

Refer to 

Diagnostic Aids 

and Go to Step 

4

4

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

—

Verify repair

Go to Step 5

5

Remove the IAT sensor and visually check. 
Was the problem found? 

—

Go to Step 8

Go to Step 6

C56(J2)

C121

1

22

ENGINE DRIVEABILITY AND EMISSIONS

6E–129

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 8

7

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) Refer to 6E-88 page.

3. Disconnect the 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 IAT sensor 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

Step

Action

Value(s)

Yes

No

Temperature (°C)

Resistance (

Ω) (Approximately)

-20

32500

0

9910

20

3400

40

1509

60

670

80

329

100

182

120

101

2

1

IAT Sensor

Ω

1

2

J2-1

J2-22

Breaker Box

Ω

Ω

C56(J2)

1

22