Isuzu N-Series. Manual - part 715

6E-282    Engine Control System (4HK1) 

Chart for with ABS but without Smoother

30

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 31

—

31

1.

Reconnect all previously disconnected
harness connector(s).

2.

Clear the DTCs with the Tech 2.

3.

Turn OFF the ignition for 30 seconds.

4.

Start the engine.

Did the DTC fail this ignition?

—

Go to Step 3

Go to Step 32

32

Observe the DTC Information with the Tech 2.

Are there any DTCs that you have not diagnosed?

—

Go to Diagnostic 

Trouble Code (DTC) 

List

System OK

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.

Monitor the engine control module (ECM)
Diagnostic Trouble Code (DTC) Information
with the Tech 2.

4.

Start the engine.

Does the DTC fail this ignition?

—

Go to Step 3

Go to Diagnostic 

Aids

3

Attempt to communicate with the electrical
hydraulic control unit (EHCU) (ABS module) via the
ABS Data table.

Does the Tech 2 communicate with the EHCU?

—

Go to Step 4

Go to Diagnostic 

System Check – 

Anti-lock Brake 

System Controls

4

1.

Turn OFF the ignition.

2.

Measure the resistance across the controller
area network (CAN) Low and High circuits by
back probing the resistor 1 (pins 1 and 2 of B-
387 connector) (resistor 1 is located near the
driver’s side dash panel. It is blue connector).

Is the resistance within the specified value (parallel
resistance of the 120 

Ω resister 1 and the 120 Ω

resistor 2 should be 60 

Ω)?

50 – 70 

Ω

Go to Step 12

Go to Step 5

5

Is the resistance less than the specified value at
Step 4?

—

Go to Step 6

Go to Step 10

6

1.

Keep the DMM with connected.

2.

Disconnect the EHCU harness connector.

Is the resistance within the specified value?

110 – 130 

Ω

Go to Step 7

Go to Step 20

7

Measure the resistance across the CAN Low and
High circuits by back probing the resistor 2 (pins 1
and 2 of B-431 connector) (resistor 2 is located
behind the radio and above the heater unit. It is
blue connector).

Is the resistance within the specified value?

110 – 130 

Ω

Go to Step 29

Go to Step 8

Step

Action

Value(s)

Yes

No

 Engine Control System (4HK1)    6E-283

8

1.

Keep the DMM with connected.

2.

Disconnect the engine control module (ECM)
harness connectors.

Is the resistance within the specified value?

110 – 130 

Ω

Go to Step 30

Go to Step 9

9

1.

Keep the DMM with connected.

2.

Disconnect the data recording module (DRM)
harness connector (DRM is located behind the
glove box).

Is the resistance within the specified value?

110 – 130 

Ω

Go to Step 28

Go to Step 21

10

1.

Disconnect the resistor 1 harness connector.

2.

Measure the resistance of the resistor 1.

Is the resistance within the specified value?

110 – 130 

Ω

Go to Step 11

Go to Step 26

11

1.

Disconnect the resister 2 harness connector
(resistor 2 is located behind the radio and
above the heater unit. It is blue connector).

2.

Measure the resistance of the resistor 2.

Is the resistance within the specified value?

110 – 130 

Ω

Go to Step 22

Go to Step 27

12

1.

Disconnect the resistor 1 and resistor 2
harness connector.

2.

Turn ON the ignition, with the engine OFF.

3.

Connect a DMM between the CAN Low circuit
(pin 1 of B-387 connector) and a known good
ground at the resistor 1 harness connector.
Record the voltage reading.

4.

Connect a DMM between the CAN High circuit
(pin 2 of B-387 connector) and a known good
ground at the resistor 1 harness connector.
Record the voltage reading.

Are both voltage readings within the specified
value?

1.3 – 3.7 volts

Go to Step 13

Go to Step 15

13

1.

Turn OFF the ignition.

2.

Disconnect the ECM harness connectors.

3.

Disconnect the EHCU harness connector.

4.

Turn ON the ignition, with the engine OFF.

5.

Connect a DMM between the CAN Low circuit
(pin 1 of B-431 connector) and a known good
ground at the resistor 2 harness connector.
Record the voltage reading.

6.

Connect a DMM between the CAN High circuit
(pin 2 of B-431 connector) and a known good
ground at the resistor 2 harness connector.
Record the voltage reading.

Are both voltage readings within the specified
value?

1.3 – 3.7 volts

Go to Step 14

Go to Step 18

Step

Action

Value(s)

Yes

No

6E-284    Engine Control System (4HK1) 

14

1.

Turn OFF the ignition.

2.

Reconnect the ECM harness connectors.

3.

Disconnect the DRM harness connectors.

4.

Turn ON the ignition, with the engine OFF.

5.

Connect a DMM between the CAN Low circuit
(pin 1 of B-431 connector) and a known good
ground at the resistor 2 harness connector.
Record the voltage reading.

6.

Connect a DMM between the CAN High circuit
(pin 2 of B-431 connector) and a known good
ground at the resistor 2 harness connector.
Record the voltage reading.

Are both voltage readings within the specified
value?

1.3 – 3.7 volts

Go to Diagnostic 

Aids

Go to Step 19

15

1.

Turn OFF the ignition.

2.

Disconnect the ECM harness connectors.

3.

Disconnect the EHCU harness connector.

4.

Disconnect the DRM harness connector.

5.

Turn ON the ignition, with the engine OFF.

6.

Test the CAN Low and CAN High circuits
among the resistor 1, resistor 2, ECM, EHCU
and DRM for a short to ground and short to
voltage.

Did you find and correct the condition?

—

Go to Step 31

Go to Step 16

16

1.

Turn OFF the ignition.

2.

Keep the ECM and DRM harness connectors
with disconnect.

3.

Reconnect the EHCU harness connector.

4.

Turn ON the ignition, with the engine OFF.

5.

Connect a DMM between the CAN Low circuit
(pin 1 of B-387 connector) and a known good
ground at the resistor 1 harness connector.
Record the voltage reading.

6.

Connect a DMM between the CAN High circuit
(pin 2 of B-387 connector) and a known good
ground at the resistor 1 harness connector.
Record the voltage reading.

Are both voltage readings within the specified
value?

1.3 – 3.7 volts

Go to Step 17

Go to Step 29

17

1.

Turn OFF the ignition.

2.

Reconnect the ECM harness connectors.

3.

Turn ON the ignition, with the engine OFF.

4.

Connect a DMM between the CAN Low circuit
(pin 1 of B-387 connector) and a known good
ground at the resistor 1 harness connector.
Record the voltage reading.

5.

Connect a DMM between the CAN High circuit
(pin 2 of B-387 connector) and a known good
ground at the resistor 1 harness connector.
Record the voltage reading.

Are both voltage readings within the specified
value?

1.3 – 3.7 volts

Go to Step 28

Go to Step 30

Step

Action

Value(s)

Yes

No

 Engine Control System (4HK1)    6E-285

18

1.

Test for an open or high resistance in the CAN
Low or High circuit (which ever voltage
reading did not read between 1.3 – 3.7 volts in
Step 13) between the DRM and joint
connection.

2.

Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 31

Go to Step 23

19

1.

Test for an open or high resistance in the CAN
Low or High circuit (which ever voltage
reading did not read between 1.3 – 3.7 volts in
Step 14) between the ECM and joint
connection.

2.

Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 31

Go to Step 25

20

Repair the short circuit each other across the CAN
Low and High circuits between the resistor 1 and
EHCU.

Did you complete the repair?

—

Go to Step 31

—

21

Repair the short circuit each other across the CAN
Low and High circuits among the resistor 2, ECM,
DRM and EHCU.

Did you complete the repair?

—

Go to Step 31

—

22

1.

Test the CAN Low and High circuits between
the resistor 1 (pins 1 and 2 of B-387
connector) and the EHCU (pins 14 and 15 of
J-177 connector) for an open circuit or high
resistance.

2.

Test the CAN Low and High circuits between
the resistor 2 (pins 1 and 2 of B-431
connector) and the EHCU (pins 26 and 27 of
J-177 connector) for an open circuit or high
resistance.

3.

Inspect for an intermittent, for poor
connections and corrosion on the CAN Low
and High circuits at the harness connector of
the each resistor.

4.

Repair the circuit(s) or connection(s) as
necessary.

Did you find and correct the condition?

—

Go to Step 31

Go to Step 24

23

1.

Inspect for an intermittent, for poor
connections and corrosion on the CAN Low
and High circuits at the harness connector of
the DRM (pins 2 and 8 of B-429 connector).

2.

Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 31

Go to Step 28

24

1.

Inspect for an intermittent, for poor
connections and corrosion on the CAN Low
and High circuits at the harness connector of
the EHCU (pins 14, 15, 26 and 27 of J-177
connector).

2.

Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 31

Go to Step 29

Step

Action

Value(s)

Yes

No