Isuzu N-Series. Manual - part 720

6E-302    Engine Control System (4HK1) 

6

1.

Lift the driving wheels or drive the vehicle.

2.

Turn ON the exhaust brake.

3.

Let the vehicle run so that the exhaust brake
may operate enough.

Does the exhaust brake operate (note that if the
vehicle speed is reduced but engine valve noise is
heard, intake throttle valve may not be operated)?

—

Go to Step 7

Go to Step 10

7

1.

Turn ON the exhaust brake switch.

2.

Let the vehicle run so that the exhaust brake
may operate enough.

3.

Press the accelerator pedal during the
exhaust brake is operating.

Does the exhaust brake cancel?

—

Go to Step 8

Observe the 

Accelerator Pedal 

Position (APP) 

Angle parameter 
and refer to APP 

sensor DTC

8

Notice:
If the vehicle fitted with Smoother, skip to Step 9.

1.

Turn ON the exhaust brake switch.

2.

Let the vehicle run so that the exhaust brake
may operate enough.

3.

Press the clutch pedal during the exhaust
brake is operating.

Does the exhaust brake cancel?

—

System OK

Go to Step 18

9

1.

Turn ON the exhaust brake switch.

2.

Let the vehicle run so that the exhaust brake
may operate enough.

3.

Operate the selector lever during the exhaust
brake is operating.

Does the exhaust brake cancel?

—

System OK

Refer to Diagnostic 

System Check – 

Transmission 

Controls

10

1.

Turn ON the exhaust brake switch.

2.

Trigger the Snapshot function in order to
capture and store engine parameters while
the vehicle is running.

3.

Let the vehicle run so that the exhaust brake
may operate enough.

4.

Review the Exhaust Brake Solenoid
Command parameter with the Tech 2 in order
to see the specific running conditions.

Does the Exhaust Brake Solenoid Command
parameter indicate ON when the exhaust brake
may operate enough?

—

Problem is relating 

to either solenoid 

valves, throttle 

valves and vacuum 

pressure lines. 

Refer to applicable 

diagnostic chart in 

the Exhaust System 

Section

The ECM is not 

allowing exhaust 

brake control. Refer 

to Condition for 

Running the 

Exhaust Brake 

Control

11

1.

Turn OFF the ignition.

2.

Disconnect the intake throttle solenoid valve
harness connector.

3.

Connect a test lamp between the voltage feed
circuit of the intake throttle solenoid valve
harness (pin 1 of J-40 connector) and a known
good ground.

4.

Turn ON the ignition, with the engine OFF.

Does the test lamp illuminate?

—

Go to Step 12

Go to Step 14

Step

Action

Value(s)

Yes

No

 Engine Control System (4HK1)    6E-303

12

1.

Connect a test lamp across the intake throttle
solenoid valve harness (pin 1 and 2 of J-40
connector).

2.

Turn ON the ignition, with the engine OFF.

3.

Perform the Exhaust Brake Control test with
the Tech 2.

4.

Command the Exhaust Brake ON with the
Tech 2.

Does the test lamp illuminate when commanded
ON with the Tech 2, then goes out?

—

Go to Step 15

Go to Step 13

13

1.

Test the control circuit of the intake throttle
solenoid valve between the engine control
module (ECM) (pin 102 of E-111 connector)
and the intake throttle solenoid valve (pin 2 of
J-40 connector) for the following conditions:

• An open circuit
• A short to ground
• A short to battery or ignition voltage
• High resistance

2.

Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 30

Go to Step 16

14

Repair the open circuit or high resistance on the
voltage feed circuit between the ECM (10A) fuse
and the intake throttle solenoid valve (pin 1 of J-40
connector).

Did you complete the repair?

—

Go to Step 30

—

15

1.

Turn OFF the ignition.

2.

Disconnect the intake throttle valve.

3.

Inspect for an intermittent and for poor
connections at the harness connector of the
intake throttle solenoid valve (pins 1 and 2 of
J-40 connector).

4.

Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 30

Go to Step 17

16

1.

Turn OFF the ignition.

2.

Disconnect the ECM harness connector.

3.

Inspect for an intermittent and for a poor
connection on the intake throttle solenoid
valve control circuit at the harness connector
of the ECM (pin 102 of E-111 connector).

4.

Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 30

Go to Step 29

17

Replace the intake throttle solenoid valve.

Did you complete the replacement?

—

Go to Step 30

—

18

1.

Turn ON the ignition, with the engine OFF.

2.

Observe the Clutch Pedal Switch parameter
with the Tech 2 while fully depressing and
releasing the clutch pedal.

Does the Tech 2 indicate Applied when the clutch
pedal is applied and Released when the clutch
pedal is released?

—

Problem is 

intermittent. Refer to 

Condition for 

Running the 

Exhaust Brake 

Control

Go to Step 19

Step

Action

Value(s)

Yes

No

6E-304    Engine Control System (4HK1) 

19

1.

Check to ensure the clutch pedal switch is
adjusted correctly. The plunger should be all
the way in when the pedal is released, yet
should not impede with the clutch pedal full
upward travel.

2.

Adjust the clutch pedal switch as necessary.

Did you find and correct the condition?

—

Go to Step 30

Go to Step 20

20

1.

Turn OFF the ignition.

2.

Disconnect the clutch pedal switch harness
connector.

3.

Turn ON the ignition, with the engine OFF.

4.

Observe the Clutch Pedal Switch parameter
with the Tech 2 while momentarily jumping
across the clutch pedal switch harness
connector between pins 1 and 2 of B-89
connector.

Does the Tech 2 indicate Applied when the circuit is
jumpered and Released when the circuit is not
jumpered?

—

Go to Step 26

Go to Step 21

21

1.

Connect a test lamp between the ignition
voltage feed circuit of the clutch pedal switch
harness (pin 1 of B-89 connector) and a
known good ground.

2.

Turn ON the ignition, with the engine OFF.

Does the test lamp illuminate?

—

Go to Step 22

Go to Step 23

22

1.

Connect a test lamp between the signal circuit
of the clutch pedal switch harness (pin 2 of B-
89 connector) and a known good ground.

2.

Turn ON the ignition, with the engine OFF.

Does the test lamp illuminate?

—

Go to Step 24

Go to Step 25

23

Repair the open circuit or high resistance on the
ignition voltage feed circuit between the ENG (IG)
(10A) fuse and the clutch pedal switch (pin 1 of B-
89 connector). Check the ENG (IG) (10A) fuse is
first.

Did you complete the repair?

—

Go to Step 30

—

24

1.

Test the clutch pedal switch signal circuit
between the ECM (pin 47 of J-191 connector)
and the clutch pedal switch (pin 2 of B-89
connector) for a short to battery or ignition
voltage.

2.

Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 30

Go to Step 29

25

1.

Test the clutch pedal switch signal circuit
between the ECM (pin 47 of J-191 connector)
and the clutch pedal switch (pin 2 of B-89
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 30

Go to Step 27

Step

Action

Value(s)

Yes

No

 Engine Control System (4HK1)    6E-305

Chart 2 of 2

26

1.

Turn OFF the ignition.

2.

Inspect for an intermittent and for poor
connections at the harness connector of the
clutch pedal switch (pins 1 and 2 of B-89
connector).

3.

Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 30

Go to Step 28

27

1.

Turn OFF the ignition.

2.

Disconnect for an intermittent and for a poor
connection on the clutch pedal switch signal
circuit at the harness connector of the ECM
(pin 47 of J-191 connector).

3.

Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 30

Go to Step 29

28

Replace the clutch pedal switch. Refer to Clutch
Pedal Switch Replacement.

Did you complete the replacement?

—

Go to Step 30

—

29

Important:
Replacement ECM must be programmed.

Replace the ECM. Refer to Engine Control Module
(ECM) Replacement / Fuel Injector ID Code Data
Programming in this section.

Did you complete the replacement?

—

Go to Step 30

—

30

Reconnect all previously disconnected fuse or
harness connector(s).

Is the action complete?

—

Go to Step 2

—

Step

Action

Value(s)

Yes

No

1

1.

Start the engine, if stopped.

2.

Turn ON the exhaust brake switch.

3.

Observe the Exhaust Brake Switch parameter
with the Tech 2.

Does the Exhaust Brake Switch parameter indicate
ON?

—

Go to Step 14

Go to Step 5

2

1.

Start the engine, if stopped.

2.

Turn OFF the exhaust brake switch.

3.

Observe the Exhaust Brake Switch parameter
with the Tech 2.

Does the Exhaust Brake Switch parameter indicate
OFF?

—

Go to Step 16

Go to Step 3

3

1.

Turn OFF the ignition.

2.

Disconnect the exhaust brake switch B-69
harness connector (located on the steering
column support bracket).

3.

Start the engine.

4.

Observe the Exhaust Brake Switch parameter
with the Tech 2.

Does the Exhaust Brake Switch parameter indicate
OFF?

—

Go to Step 13

Go to Step 4

Step

Action

Value(s)

Yes

No