Isuzu N-Series. Manual - part 719

6E-298    Engine Control System (4HK1) 

7

1.

Turn ON the engine warm up switch.

2.

Press the accelerator pedal.

Does the engine warm up system cancel?

—

Go to Step 8

Observe the 

Accelerator Pedal 

Position (APP) 

Angle parameter 
and refer to APP 

sensor DTC

8

1.

Lift the driving wheels or drive the vehicle.

2.

Turn ON the engine warm up switch.

Does the engine warm up system cancel?

—

System OK

Observe the Vehicle 

Speed parameter 

and refer to DTC 

P0500

9

1.

Start the engine.

2.

Turn ON the engine warm up switch.

3.

Observe the Engine Warm Up Switch
parameter with the Tech 2.

Does the Engine Warm Up Switch parameter
indicate ON?

—

Go to Step 10

Go to Step 11

10

Observe the Exhaust Brake Solenoid Command
parameter with the Tech 2.

Does the Exhaust Brake Solenoid Command
parameter indicate ON when engine warm up
switch is ON?

—

Problem is relating 

to either solenoid 

valves, throttle 

valves and vacuum 

pressure lines. 

Refer to applicable 

diagnostic chart in 

the Exhaust System 

Section or refer to 

Exhaust Brake 

Control System 

Check

The ECM is not 
allowing engine 

warm up control. 

Refer to Condition 

for Running the 

Engine Warm Up 

Control

11

1.

Turn OFF the ignition.

2.

Remove the bezel surrounding the instrument
panel cluster (IPC) enough to disconnect the
engine warm up switch.

3.

Disconnect the engine warm up switch.

4.

Connect a test lamp between the voltage feed
circuit of the engine warm up switch harness
(pin 3 of B-31 connector) and a known good
ground.

5.

Start the engine.

Does the test lamp illuminate?

—

Go to Step 12

Go to Step 13

12

1.

Start the engine.

2.

Observe the Engine Warm Up Switch
parameter with the Tech 2 while momentarily
jumping 3-amp fused jumper wire across the
engine warm up switch harness connector
between pins 3 and 6 of B-31 connector.

Does the Tech 2 indicate ON when the circuit is
jumpered and OFF when the circuit is not
jumpered?

—

Go to Step 21

Go to Step 14

13

Repair the open circuit or high resistance on the
voltage feed circuit between the Fuel Heater (10A)
fuse and the engine warm up switch (pin 3 of B-31
connector).

Did you complete the repair?

—

Go to Step 25

—

Step

Action

Value(s)

Yes

No

 Engine Control System (4HK1)    6E-299

14

1.

Test the engine warm up switch signal circuit
between the engine control module (ECM)
(pin 51 of J-191 connector) and the engine
warm up switch (pin 6 of B-31 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 25

Go to Step 22

15

1.

Turn OFF the ignition.

2.

Remove the bezel surrounding the IPC
enough to disconnect the engine warm up
switch.

3.

Connect the engine warm up switch if
disconnected.

4.

Probe a test lamp between the engine warm
up switch indicator lamp harness (pin 4 of B-
31 connector) and a known good ground.

5.

Start the engine.

6.

Turn ON the engine warm up switch.

Does the test lamp illuminate?

—

Go to Step 16

Go to Step 17

16

1.

Probe a test lamp across the engine warm up
switch indicator lamp harness (pins 1 and 4 of
B-31 connector).

2.

Start the engine.

3.

Turn ON the engine warm up switch.

Does the test lamp illuminate?

—

Go to Step 21

Go to Step 18

17

Repair the open circuit between the engine warm
up switch signal circuit and the indicator lamp
circuit (pins 4 and 6 of B-31 connector).

Did you compete the repair?

—

Go to Step 25

—

18

Repair the open circuit or high resistance on the
engine warm up switch indicator lamp ground
circuit between the engine warm up switch (pin 1 of
B-31 connector) and ground terminal (B-1).

Did you complete the repair?

—

Go to Step 25

—

19

1.

Turn OFF the ignition.

2.

Remove the bezel surrounding the IPC
enough to disconnect the engine warm up
switch.

3.

Disconnect the engine warm up switch if
disconnected.

4.

Start the engine.

Does the engine warm up system cancel?

—

Go to Step 23

Go to Step 20

20

1.

Test the engine warm up switch signal circuit
between the ECM (pin 51 of J-191 connector)
and the engine warm up switch (pin 6 of B-31
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 25

Go to Step 24

Step

Action

Value(s)

Yes

No

6E-300    Engine Control System (4HK1) 

21

1.

Turn OFF the ignition.

2.

Disconnect the engine warm up switch
harness connector.

3.

Inspect for an intermittent and for poor
connections at the harness connector of the
engine warm up switch (pins 1, 3, 4 and 6 of
B-31 connector).

4.

Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 25

Go to Step 23

22

1.

Turn OFF the ignition.

2.

Disconnect the ECM harness connector.

3.

Inspect for an intermittent and for a poor
connection on the engine warm up switch
signal circuit at the harness connector of the
ECM (pin 51 of J-191 connector).

4.

Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 25

Go to Step 24

23

Replace the engine warm up switch.

Did you complete the replacement?

—

Go to Step 25

—

24

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 25

—

25

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

Is the action complete?

—

Go to Step 2

—

Step

Action

Value(s)

Yes

No

 Engine Control System (4HK1)    6E-301

Exhaust Brake Control System Check

Description
The exhaust brake control 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
exhaust brake switch. 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 vehicle running conditions and
exhaust brake switch input signal.

Condition for Running the Exhaust Brake Control

• The exhaust brake switch is ON.
• The accelerator pedal is not depressed.
• The clutch pedal is not depressed.
• The neutral switch is OFF (other than neutral).
• The vehicle speed is higher than predetermined

range.

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.
10. If the Exhaust Brake Solenoid Command parameter
indicates OFF, use the Tech 2 to observe the Vehicle
Speed, APP Angle, Clutch Switch and Neutral Switch
parameters which allows the exhaust brake control.
Refer to Engine Controls Schematic for each input.

Exhaust Brake 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

Chart 1 of 2

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.

Are any DTCs set in which the “Action Taken When
the DTC Sets” under that particular code states,
“The ECM inhibits exhaust brake control”?

—

Refer to Applicable 

DTC

Go to Step 3

3

1.

Start the engine.

2.

Turn ON the exhaust brake switch.

Does the exhaust brake indicator lamp in the
instrument panel cluster (IPC) illuminate?

—

Go to Step 4

Go to Chart 2 of 2 

Step 1

4

Turn OFF the exhaust brake switch.

Does the exhaust brake indicator lamp in the IPC
go out?

—

Go to Step 5

Go to Chart 2 of 2 

Step 2

5

1.

Turn ON the ignition, with the engine OFF.

2.

Perform the Exhaust Brake Control test with
the Tech 2.

3.

Command the Exhaust Brake ON with the
Tech 2.

Does the exhaust brake solenoid valve and intake
throttle solenoid valve click when commanded ON
with the Tech 2 (note that intake throttle solenoid
valve and exhaust brake solenoid valve energized
at the same time)?

—

Go to Step 6

If both solenoid 

valves or only 

exhaust brake 

solenoid valve is not 

operated, refer to 

DTC P1681 or 

P1682.

If only intake throttle 

solenoid valve is not 

operated, Go to 

Step 11