Isuzu KB P190. Manual — part 280

6E-86 Engine Control System (4JH1)

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
IAT sensor harness (pins 1 and 3 of C-116
connector).

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

110°C (230°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 IAT sensor harness (pin 1 of
C-116 connector) and a known good ground.

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

110°C (230°F)

Go to Step 8

Go to Step 7

7

1. Test the signal circuit between the ECM (pin 84

of C-57 connector) and the IAT sensor (pin 1 of
C-116 connector) for an open circuit 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 92 of C-57 connector) and the IAT sensor
(pin 3 of C-116 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 84

of C-57 connector) and the IAT sensor (pin 1 of
C-116 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

1. Turn OFF the ignition.
2. Inspect for an intermittent and for poor

connections at the harness connector of the IAT
sensor (pins 1 and 3 of C-116 connector).

3. 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 IAT sensor circuits at the
harness connector of the ECM (pins 84 and 92 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 IAT sensor. Refer to Mass Air Flow
Sensor Replacement in this section. (IAT sensor is
internal to MAF sensor)
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



Engine Control System (4JH1) 6E-87

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

6E-88 Engine Control System (4JH1)

DTC P0110 (Symptom Code 2) (Flash Code 23)

Circuit Description
The intake air temperature (IAT) sensor is fitted
between the air cleaner and turbocharger internal to the
mass air flow (MAF) sensor. The IAT sensor is a
variable resistor. The IAT sensor has a signal circuit
and a low reference circuit. The IAT sensor measures
the temperature of the air entering the engine. The
engine control module (ECM) supplies 5 volts to the IAT
signal circuit and a ground for the IAT low reference
circuit. When the IAT sensor is cold, the sensor
resistance is high. When the air temperature increases,
the sensor resistance decreases. With high sensor
resistance, the ECM detects a high voltage on the IAT
signal circuit. With lower sensor resistance, the ECM
detects a lower voltage on the IAT signal circuit. If the
ECM detects an excessively low IAT 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 IAT 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 IAT substitution of 0°C (32°F)

for engine 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.

• Use the Temperature vs. Resistance table to test

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

Notice:

• The mass air flow (MAF) sensor is heated and as

a result the IAT sensor may indicate a higher than
normal intake temperature if the ignition switch is
being ON.

DTC P0110 (Symptom Code 2) (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 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 Intake Air Temperature (IAT)

parameter with the scan tool.

Is the IAT parameter more than the specified value?

110°C (230°F)

Go to Step 3

Go to Diagnostic

Aids

3

1. Turn OFF the ignition.
2. Disconnect the mass air flow/intake air

temperature (MAF/IAT) sensor harness
connector.

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

-38°C (-36°F)

Go to Step 5

Go to Step 4

4

1. Test the signal circuit between the engine control

module (ECM) (pin 84 of C-57 connector) and
the IAT sensor (pin 1 of C-116 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

Engine Control System (4JH1) 6E-89

Step Action

Value(s)

Yes No

5

Replace the IAT sensor. Refer to Mass Air Flow
Sensor Replacement in this section. (IAT sensor is
internal to MAF sensor)
Did you complete the replacement?



Go to Step 8



6

1. Turn OFF the ignition.
2. Disconnect the ECM harness connector.
3. Inspect connections on the IAT sensor circuits at

the harness connector of the ECM (pins 84 and
92 of C-57 connector) for corrosion.

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



Go to Step 8

Go to Step 7

7

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 8



8

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 9

9

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