Isuzu N-Series. Manual - part 718

6E-294    Engine Control System (4HK1) 

Glow Control System Check

Description
The glow control system consists of the engine control
module (ECM), the glow relay, the glow indicator lamp
and glow plugs. The glow control system is operated
when the engine coolant temperature is low, which
allows easier engine starting. The ECM commands the
glow relay ON for a certain length of time at ignition
switch is ON with engine OFF. In after glow phase, the
glow plugs remain energized for a certain period with
engine run.

Glow Control Operation

• The glow control system operates when the engine

coolant temperature is less than 10

°C (50°F).

• The glow indicator lamp is illuminated between 0.5

seconds and 15 seconds according to the engine
coolant temperature. It illuminates 0.5 seconds at
10

°C (50°F) or more.

• The glow relay is energized between 1 second and

30 seconds according to the engine coolant
temperature. It energizes 1 second at 10

°C (50°F)

or more.

Glow Control System Check
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 Tech 2.

2.

Turn OFF the ignition for 30 seconds.

3.

Turn ON the ignition, with the engine OFF.

4.

Monitor the Diagnostic Trouble Code (DTC)
Information with the Tech 2.

Is DTC P0117, P0118, P0380 or P0381 set?

—

Refer to Applicable 

DTC

Go to Step 3

3

1.

Turn OFF the ignition.

2.

Make sure the metal bus bar that connects
switched battery voltage supply terminal (E-3)
and all glow plugs is secured tightly.

3.

Turn ON the ignition, with the engine OFF.

4.

Connect a test lamp between the metal bus
bar (glow plug power supply E-3 terminal) and
a known good ground.

5.

Perform the Glow Relay Test with the Tech 2.

6.

Command the Glow Relay ON with the Tech 2
while observing the test lamp.

Does the test lamp turn ON only when commanded
ON with the Tech 2?

—

Go to Step 4

Go to Step 5

4

1.

Turn OFF the ignition.

2.

Remove the metal bus bar from the glow
plugs.

3.

Measure resistance of each glow plug
between the glow plug terminals and a known
good ground. Make sure to record all
measurements and take them quickly as to
not allow engine temperature changes
between measurements.

Are the resistances within the specified value each
other?

1 

Ω

System OK

Go to Step 15

 Engine Control System (4HK1)    6E-295

5

1.

Turn OFF the ignition.

2.

Replace the glow relay with the starter relay or
replace with a known good relay.

3.

Turn ON the ignition, with the engine OFF.

4.

Connect a test lamp between the metal bus
bar (glow plug power supply E-3 connector)
and a known good ground.

5.

Perform the Glow Relay Test with the Tech 2.

6.

Command the Glow Relay ON with the Tech 2
while observing the test lamp.

Does the test lamp turn ON only when commanded
ON with the Tech 2?

—

Go to Step 9

Go to Step 6

6

Inspect the Glow (60A) slow blow fuse in the
chassis side fuse & relay box.

Is the Glow (60A) slow blow fuse open?

—

Go to Step 10

Go to Step 7

7

1.

Turn OFF the ignition.

2.

Remove the glow relay in the chassis side
fuse & relay box.

3.

Connect a test lamp between the voltage feed
circuit of the glow relay terminal (pin 3 of X-20
connector) and a known good ground.

4.

Turn ON the ignition, with the engine OFF.

Does the test lamp illuminate?

—

Go to Step 8

Go to Step 11

8

1.

Turn ON the ignition, with the engine OFF.

2.

Connect a test lamp between the power
supply circuit to the glow plugs (pin 2 of X-20
connector) and a known good ground.

Does the test lamp illuminate?

—

Go to Step 13

Go to Step 12

9

1.

Turn OFF the ignition.

2.

Inspect for an intermittent and for poor
connections at the glow relay terminals (pins 2
and 3 of X-20 connector).

3.

Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 16

Go to Step 14

10

1.

Replace the Glow (60A) slow blow fuse. If the
slow blow fuse continues to open, repair the
short to ground on a circuit fed by the slow
blow fuse or check for a shorted attached
component.

2.

Repair the short to ground or replace the
component as necessary.

Did you complete the repair?

—

Go to Step 16

—

11

Repair the open circuit in the battery voltage supply
circuit between the Glow (60A) slow blow fuse and
the glow relay (pin 3 of X-20 connector).

Did you complete the repair?

—

Go to Step 16

—

12

Repair the open circuit in the switched battery
voltage supply circuit between the glow relay (pin 2
of X-20 connector) and the glow plugs (E-3
terminal).

Did you complete the repair?

—

Go to Step 16

—

Step

Action

Value(s)

Yes

No

6E-296    Engine Control System (4HK1) 

13

Important:
The glow plugs may be burnt out if the battery
voltage supply circuit is shorted to a voltage
source.

Repair the short to battery or ignition voltage on the
switched battery voltage supply circuit between the
glow relay (pin 2 of X-20 connector) and the glow
plugs (E-3 terminal).

Did you complete the repair?

—

Go to Step 16

—

14

Replace the glow relay.

Did you complete the replacement?

—

Go to Step 16

—

15

Replace the appropriate glow plug.

Did you complete the replacement?

—

Go to Step 16

—

16

1.

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

2.

Turn OFF the ignition for 30 seconds.

3.

Turn ON the ignition, with the engine OFF.

4.

Connect a test lamp between the metal bus
bar (glow plug power supply E-3 connector)
and a known good ground.

5.

Perform the Glow Relay Test with the Tech 2.

6.

Command the Glow Relay ON with the Tech 2
while observing the test lamp.

Does the test lamp turn ON only when commanded
ON with the Tech 2?

—

Go to Step 4

Go to Step 5

Step

Action

Value(s)

Yes

No

 Engine Control System (4HK1)    6E-297

Engine Warm Up Control System Check

Description
The engine warm up system consists of the engine
control module (ECM), the intake throttle valve, the
intake throttle solenoid valve, the exhaust brake valve,
the exhaust brake solenoid valve and the engine warm
up switch. The engine warm up system is operated
when the engine coolant temperature is low, which
promotes engine warm up. The ECM commands the
both intake throttle solenoid valve and the exhaust
brake solenoid valve to close each valve by applying
vacuum pressure based on engine coolant temperature
and warm up request switch input signal.

Condition for Running the Engine Warm Up Control

• The engine warm up switch is ON.
• The accelerator pedal is not depressed.
• The engine coolant temperature is less than 65

°C

(149

°F).

• The vehicle is stationary.

Test Description
The number below refers to the step number on the
diagnostic table.
7. Use the Tech 2 to observe the Accelerator Pedal
Position (APP) Angle. The APP Angle parameter
should change linearly from 0% to 100% according to
the accelerator pedal operation.
8. Use the Tech 2 to observe the Vehicle Speed. The
Vehicle Speed parameter should indicate correct
vehicle speed.

Engine Warm Up Control System Check
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

Does the exhaust brake operate correctly?

—

Go to Step 3

Go to Exhaust 

Brake Control 

System Check

3

1.

Install the Tech 2.

2.

Turn OFF the ignition for 30 seconds.

3.

Turn ON the ignition, with the engine OFF.

4.

Monitor the Diagnostic Trouble Code (DTC)
Information with the Tech 2.

Is DTC P0117, P0118, P1271, P1277, P1278,
P1282, P1283, P1631, P1632, P1635, P1681 or
P1682 set?

—

Refer to Applicable 

DTC

Go to Step 4

4

1.

Park the vehicle.

2.

Make sure the idle up control knob to the
lowest position. (Full counterclockwise
direction)

3.

Cool down the engine as necessary (allow
engine coolant temperature to cool down at
least 60

°C [140°F]).

4.

Start the engine.

5.

Turn ON the engine warm up switch.

Are the intake throttle valve and the exhaust brake
valve closed when switched ON?

—

Go to Step 5

Go to Step 9

5

Does the engine warm up switch indicator lamp
illuminate?

—

Go to Step 6

Go to Step 15

6

Turn OFF the engine warm up switch.

Does the engine warm up system cancel?

—

Go to Step 7

Go to Step 19