Isuzu D-Max / Isuzu Rodeo (TFR/TFS). Manual - part 74

4JA1-TC/4JH1-TC ENGINE DRIVEABILITY AND EMISSIONS

6E–291

Diagnostic Trouble Code (DTC) P1611 (Symptom Code A) (Flash Code 56) 

Wrong Security Code Entered

Step

Action

Value(s)

Yes

No

1

Was the “On-Board Diagnostic (OBD) System Check”
performed?

—

Go to Step 2

Go to On Board 

Diagnostic 

(OBD) System 

Check

2

1. Connect the Tech 2. 

2. Review and record the failure information. 

3. Select “F0: Read DTC Infor As Stored By ECU” in

“F0: Diagnostic Trouble Codes”. 

Is the DTC P1611 (Symptom Code A) stored as
“Present Failure”?

—

Go to Step 3

Refer to 

Diagnostic Aids 

and Go to Step 

3

3

1. Using the Tech 2, ignition “On” and engine “Off”. 

2. Select  “F1: Clear DTC Information” in “F0:

Diagnostic Trouble Codes” with the Tech 2 and
clear the DTC information. 

3. Operate the vehicle and monitor the “F0: Read

DTC Infor As Stored By ECU” in the “F0:
Diagnostic Trouble Codes”. 

Was the DTC P1611 (Symptom Code A) stored in this
ignition cycle?

—

Go to Step 4

Refer to 

Diagnostic Aids 

and Go to Step 

4

4

1. Using the Tech 2, ignition “On” and engine “Off”. 

2. Select “Immobiliser” in the system selection menu

“Body”. 

3. Select “Read DTC Info Ordered By Priority” in the

“Diagnostic Trouble Code”. 

Was the any DTC's B**** stored in this ignition cycle?

—

Refer to 

“Immobiliser 

Workshop 

Manual” & Go 

to DTC Chart 

B**** 

Go to Step 5

5

Is the ECM programmed with the latest software
release? 
If not, download the latest software to the ECM using
the “SPS (Service Programming System)”. 
Was the problem solved?

—

Verify repair

Go to Step 6

6

Replace the ECM. 
Is the action complete? 
IMPORTANT: The replacement ECM must be
programmed. Refer to section of the Service
Programming System (SPS) in this manual. 
Following ECM programming, the immobiliser system
(if equipped) must be linked to the ECM. Refer to
section 11 “Immobiliser System-ECM replacement” for
the ECM/Immobiliser linking procedure.

—

Verify repair

—

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4JA1-TC/4JH1-TC ENGINE DRIVEABILITY AND EMISSIONS

DIAGNOSTIC TROUBLE CODE (DTC) P1612 (SYMPTOM CODE A) 

(FLASH CODE 56) IMMOBILISER NO OR WRONG SIGNAL

Condition for setting the DTC and action taken when the DTC sets

Circuit Description

The ECM decides whether that is an abnormality in the
immobiliser control system. DTC P1612 (Symptom
Code A) is recorded when received immobiliser
challenge signal was not correct.

Diagnostic Aids

Check for the following conditions:

• Poor connection at ECM and immobiliser control unit-

Inspect harness connectors for backed out terminals,
improper mating, broken locks, improperly formed or
damaged terminals, and poor terminal to wire
connection.

• Damaged harness-Inspect the wiring harness for

damage. If the harness appears to be OK, observe
the DTC P1612 display on the Tech2 while moving
connectors and wiring harnesses. 

Flash 

Code

Code

Symptom 

Code

MIL

DTC Name

DTC Setting Condition

Fail-Safe (Back Up)

56

P1612

A

-

Immobiliser No or Wrong Sig-
nal

Received challenge signal is 
not correct or not received.

1. Engine does not start. 
2. Check engine lamp flash. 

Ignition
SW

Meter
15A

6 15

7

Batt

Batt

0.5
RED/
WHT

29

0.5
ORG/
BLU

43

0.5
BRN/
YEL

42

0.5
BLK/
RED

27

0.5
BLU/
WHT

0.5 BLU/BLK

68

0.5
WHT

2.0
BLK

35

VSS

0.85
YEL

Imnobiliser

Control Unit

7

8

0.5
BRN/
YEL

IC

0.85
YEL

Glow

Check

Engine

Tacho

Meter

Speed

Meter

A/T

TCM

µP

µP

µP

µP

Engine
Control
Module
(ECM)

4JA1-TC/4JH1-TC ENGINE DRIVEABILITY AND EMISSIONS

6E–293

Diagnostic Trouble Code (DTC) P1612 (Symptom Code A) (Flash Code 56) 

Immobiliser No or Wrong Signal

Step

Action

Value(s)

Yes

No

1

Was the “On-Board Diagnostic (OBD) System Check”
performed?

—

Go to Step 2

Go to On Board 

Diagnostic 

(OBD) System 

Check

2

1. Connect the Tech 2. 

2. Review and record the failure information. 

3. Select “F0: Read DTC Infor As Stored By ECU” in

“F0: Diagnostic Trouble Codes”. 

Is the DTC P1612 (Symptom Code A) stored as
“Present Failure”?

—

Go to Step 3

Refer to 

Diagnostic Aids 

and Go to Step 

3

3

1. Using the Tech 2, ignition “On” and engine “Off”. 

2. Select  “F1: Clear DTC Information” in “F0:

Diagnostic Trouble Codes” with the Tech 2 and
clear the DTC information. 

3. Operate the vehicle and monitor the “F0: Read

DTC Infor As Stored By ECU” in the “F0:
Diagnostic Trouble Codes”. 

Was the DTC P1612 (Symptom Code A) stored in this
ignition cycle?

—

Go to Step 4

Refer to 

Diagnostic Aids 

and Go to Step 

4

4

1. Using the Tech 2, ignition “On” and engine “Off”. 

2. Select “Immobiliser” in the system selection menu

“Body”. 

3. Select “Read DTC Info Ordered By Priority” in the

“Diagnositic Trouble Code”. 

Was the any DTC's B**** stored in this ignition cycle?

—

Refer to 

“Immobiliser 

Workshop 

Manual” & Go 

to DTC Chart 

B**** 

Go to Step 5

5

Check for poor/faulty connection at the immobiliser
control unit connector or ECM connector. If a poor/
faulty connection is found, repair as necessary. 
Was the problem found?

—

Verify repair

Go to Step 6

42

35

7

8

C-56

B-68

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4JA1-TC/4JH1-TC ENGINE DRIVEABILITY AND EMISSIONS

6

Using the DVM and check the “CHECK ENGINE”
lamp circuit.

1.  Ignition “Off”, engine “Off”. 

2. Disconnect the meter connector and immobiliser

control unit connector. 

3. Ignition “On”. 

4. Check the circuit for short to power supply circuit. 

Was DVM indicated specified value?

Less than 1V

Go to Step 7

Repair faulty 
harness and 

verify repair

Step

Action

Value(s)

Yes

No

7

V

B-68