Isuzu KB P190. Manual — part 309

6E-202 Engine Control System (4JH1)

Step Action

Value(s)

Yes

No

12

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

APP sensor connector between pins 2 and 3 of
the E-22 connector.

3. Turn ON the ignition, with the engine OFF.
Does DTC P1120 (Symptom Code 1) set, but not
P1120 (Symptom Code E)?



Go to Step 15

Go to Step 14

13

1. Test the 5 volts reference circuit between the

engine control module (ECM) (pin 57 of C-56
connector) and the APP sensor (pin 3 of E-22
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 21

Go to Step 18

14

1. Test the signal circuit between the ECM (pin 38

of C-56 connector) and the APP sensor (pin 2 of
E-22 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 21

Go to Step 18

15

1. Test the signal circuit between the ECM (pin 38

of C-56 connector) and the APP sensor (pin 2 of
E-22 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 21

Go to Step 16

16

1. Test the low reference circuit between the ECM

(pin 49 of C-56 connector) and the APP sensor
(pin 1 of E-22 connector) for high resistance.

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



Go to Step 21

Go to Step 17

17

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

connections or corrosion at the harness
connector of the APP sensor (pin 1, 2 and 3 of E-
22 connector).

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



Go to Step 21

Go to Step 19

18

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

connections on the APP sensor circuits at the
harness connector of the ECM (pins 38, 49 and
57 of C-56 connector) or the idle switch circuit at
the harness connector of the ECM (pin 69 of C-
56 connector).

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



Go to Step 21

Go to Step 20

19

Replace the accelerator pedal position sensor. Refer
to Accelerator Pedal Position Sensor Replacement
in this section. (Idle switch is part of APP sensor)
Did you complete the replacement?



Go to Step 21



20

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 21



Engine Control System (4JH1) 6E-203

Step Action

Value(s)

Yes

No

21

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. Turn ON the ignition, with the engine OFF.
5. Observe the Idle Switch and APP parameter

while fully depressing and releasing the
accelerator pedal many times.

Does the scan tool indicate the APP parameter
smoothly changed within 0 to 100 % when the
accelerator pedal is depressed and released, then
scan tool indicate the Idle Switch parameter OFF
when the accelerator pedal is depressed and ON
when the accelerator pedal is released?



Go to Step 22

Go to Step 2

22

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-204 Engine Control System (4JH1)

DTC P1173 (Symptom Code 3) (Flash Code 22)

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 excessive high coolant temperature,
this DTC will set.
Condition for Running the DTC

• The ignition switch is ON.

Condition for Setting the DTC

• The ECM detects an excessive high coolant

temperature for longer than 30 seconds.

Action Taken When the DTC Sets

• The ECM does not illuminate the malfunction

indicator lamp (MIL) when the diagnostic runs and
fails.

Condition for Clearing the DTC

• 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.

Notice:

• This DTC is caused by an engine overheat

condition (i.e. low engine coolant level). Since this
DTC does not illuminate any lamps, clear the DTC
and ensure there are no signs of engine damage.
Excessive engine overheat may damage internal
engine components.

DTC P1173 (Symptom Code 3) (Flash Code 22)

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 OFF the ignition for 30 seconds.
3. Start the engine and wait until engine is fully

warms upped.

4. Observe the Engine Coolant Temperature (ECT)

parameter with the scan tool.

Is the ECT parameter more than the specified
value?

100°C (212°F)

Go to Step 4

Go to Step 3

3

Ask the driver if overheat is caused by low engine
coolant level, etc.
If engine overheat has experienced, the engine must
be inspected and repaired as necessary.
Did you complete the action?



Go to Step 6



4

1. Test the ECT sensor at various temperature

levels to evaluate the possibility if a skewed
sensor.

2. Replace the ECT sensor as necessary.
Did you find and correct the condition?



Go to Step 6

Go to Step 5

Engine Control System (4JH1) 6E-205

Step Action

Value(s)

Yes

No

5

1. Test the engine cooling system for the following

condition. Refer to diagnosis of the engine
cooling system section for testing.

• Engine coolant level
• Engine coolant leakage
• Cooling fan belt slippage
• Cooling fan clutch working
• Thermostat

working

• Water pump working
• Radiator

clogging

2. Repair or replace as necessary.
Did you find and correct the condition?



Go to Step 6

Go to Diagnostic

Aids

6

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 and wait until engine is fully

warms upped.

5. Observe the ECT parameter with the scan tool.
Is the ECT parameter more than the specified
value?

100°C (212°F)

Go to Step 4

Go to Step 7

7

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