Isuzu KB P190. Manual - part 419

ENGINE CONTROL SYSTEM (4JK1/4JJ1)   6E-59

12

1.

Turn OFF the ignition.

2.

Reconnect the ECM J1 (E-90) and J2 (C-58)
harness connectors if disconnected.

3.

Reconnect the TCM C-94 and C-95 harness
connectors if disconnected.

4.

Disconnect the instrument panel (IP) cluster
B-23 and B-24 harness connector.

5.

Turn ON the ignition, with the engine OFF.

6.

Attempt to communicate with the ECM and
TCM.

Does the scan tool communicate with the ECM and
TCM?

—

Go to Step 18

Go to Step 13

13

Repair the open circuit, short to ground or short to
voltage on the CAN Low or High serial data circuit
between the DLC and ECM, TCM, ICU, DRM or IP
cluster.

Did you complete the repair?

—

Go to Step 19

—

14

Replace the DRM. Refer to DRM Replacement.

Did you complete the replacement?

—

Go to Step 19

—

15

Important: Replacement ECM must be
programmed and learned.
Replace the ECM.  Refer to ECM Replacement.

Did you complete the replacement?

—

Go to Step 19

—

16

Important: Replacement TCM must be
programmed.
Replace the TCM.  Refer to TCM Replacement.

Did you complete the replacement?

—

Go to Step 19

—

17

Important: Replacement ICU must be
programmed.
Replace the ICU.  Refer to ICU Replacement.

Did you complete the replacement?

—

Go to Step 19

—

18

Replace the IP cluster. Refer to IP Cluster
Replacement.

Did you complete the replacement?

—

Go to Step 19

—

19

Attempt to establish communication with the ECM,
TCM and ICU.

Does the scan tool communicate with the ECM,
TCM and ICU?

—

System OK

Go to Step 2

Step

Action

Value(s)

Yes

No

6E-60   ENGINE CONTROL SYSTEM (4JK1/4JJ1)

Lost Communication with The Engine Control Module (ECM)

Circuit Description

The ECM, transmission control module (TCM) (AISIN
A/T only) and immobilizer control unit (ICU) all
communicate with the scan tool over the controller area
network (CAN) link. The ECM, TCM, ICU and the data
recording module (DRM) communicate with each other
over the same CAN link. If no immobilizer system is
installed, the instrument panel (IP) cluster has a CAN
terminating resistor instead of the ICU.

Schematic Reference: Engine Controls Schematics

Connector End View Reference: Engine Controls
Connector End Views or ECM Connector End Views

Circuit/ System Testing Lost Communication with The Engine Control Module (ECM)

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

Attempt to establish communication with the ECM.
Does the scan tool communicate with the ECM?

—

Go to Intermittent 

Conditions

Go to Step 3

3

Check the ECM C-58 and E-90 connectors for poor
connections.

Did you find and correct the condition?

—

Go to Step 16

Go to Step 4

4

1.

Check the ECM (40A) slow blow fuse, ECM
(B) (10A) fuse and Engine (10A) fuse.
Replace and retest if open. If any fuse
continues to open, repair the short to ground
on each circuit fed by that fuse.

2.

Turn OFF the ignition.

3.

Disconnect the ECM C-58 harness connector.

4.

Turn ON the ignition, with the engine OFF.

5.

Connect a test lamp to ground and check for
voltage at the ignition voltage supply circuit at
the ECM (pin 72 of C-58).

Does the test lamp illuminate?

—

Go to Step 5

Go to Step 13

5

1.

Turn OFF the ignition.

2.

Disconnect the scan tool from the data link
connector (DLC) if connected.

3.

Measure the resistance across the CAN Low
and High circuits by probing the DLC (pins 6
and 14 of B-58).

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

Ω resistor in the ECM and the

120 

Ω resistor in the ICU or IP cluster should be

60

Ω)?

50 to 70 

Ω

Go to Step 7

Go to Step 6

6

1.

Turn OFF the ignition.

2.

Disconnect the ECM harness connector.

3.

Inspect for an intermittent, for poor
connections and corrosion at the harness
connector of the ECM (pins 66 and 67 of C-
58).

4.

Test for high resistance on each circuit.

5.

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

Did you find and correct the condition?

—

Go to Step 16

Go to Step 15

ENGINE CONTROL SYSTEM (4JK1/4JJ1)   6E-61

7

1.

Check ECM ground for corrosion and
tightness.

2.

Clean or tighten grounds as necessary.

Did you find and correct the condition?

—

Go to Step 16

Go to Step 8

8

1.

Turn OFF the ignition.

2.

Reconnect the ECM harness connector if
disconnected.

3.

Replace the ECM main relay with the heater
relay or replace with a known good relay.

4.

Turn ON the ignition, with the engine OFF.

5.

Attempt to establish communication with the
ECM.

Does the scan tool communicate with the ECM?

—

Go to Step 14

Go to Step 9

9

1.

Turn OFF the ignition.

2.

Remove the ECM main relay.

3.

Turn ON the ignition, with the engine OFF.

4.

Using a test lamp, check for both voltage
supply circuits to the ECM main relay (pins 4
and 5 of X-12).

5.

Repair the open circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 16

Go to Step 10

10

1.

Reinstall the ECM main relay.

2.

Turn the ignition ON and OFF while listening
of feeling for the ECM main relay click. Wait 7
seconds between transitions.

Does the ECM main relay click when the ignition
switch is turned ON or OFF?

—

Go to Step 12

Go to Step 11

11

Repair the ECM main relay ground circuit between
the ECM main relay (pin 2 of X-12) and engine
room ground terminal (C-36) for the following
conditions:

• An open circuit

• High resistance or a poor connection at the

ECM main relay or ground terminal

Did you complete the repair?

—

Go to Step 16

—

12

1.

Test the battery voltage circuit between the
ECM (pin 73 of C-58) and the ECM main relay
(pin 1 of X-12) for the following conditions:

• An open circuit

• High resistance or a poor connection at

ECM or ECM main relay

2.

Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 16

Go to Step 15

13

Repair the open in the ignition voltage circuit to the
ECM.

Did you complete the repair?

—

Go to Step 16

—

14

Replace the ECM main relay.

Did you complete the replacement?

—

Go to Step 16

—

Step

Action

Value(s)

Yes

No

6E-62   ENGINE CONTROL SYSTEM (4JK1/4JJ1)

15

Important: Replacement ECM must be
programmed and learned.
Replace the ECM.  Refer to ECM Replacement.

Did you complete the replacement?

—

Go to Step 16

—

16

1.

Turn OFF the ignition.

2.

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

3.

Turn ON the ignition, with the engine OFF.

4.

Attempt to establish communication with the
ECM.

Does the scan tool communicate with the ECM?

—

System OK

Go to Step 3

Step

Action

Value(s)

Yes

No