Isuzu KB P190. Manual - part 302

6E-174  Engine Control System (4JH1) 

DTC P0602 

Description 
The engine control module (ECM) has the ability to set
a diagnostic trouble code (DTC) if it detects that there is 
no vehicle identification (VIN) programmed. 
 

 

Diagnostic Aids 
Notice: 

•  Production and service ECM does not require 

software programming when it is replaced except 
calibration software update. This DTC indicates 
that a production or service ECM does not 
program VIN. 

 
DTC P0602 

 

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 scan tool. 
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 scan tool. 

Does the DTC fail this ignition? 

 

Go to Step 3 

Go to Step 6 

3 

Important: Blank engine control module (ECM) must 
be programmed. 
Program the ECM. Refer to Engine Control Module 
(ECM) Replacement in this section. 
Did you complete the programming? 

 

Go to Step 4 

 

4 

1.  Clear the DTCs with the scan tool. 
2.  Turn OFF the ignition for 30 seconds. 
3.  Turn ON the ignition, with the engine OFF. 
4.  Monitor the DTC Information with the scan tool. 
Does the DTC fail this ignition? 

 

Go to Step 5 

Go to Step 7 

5 

Important: Replacement ECM must be 
programmed. 
Replace the ECM. Refer to Engine Control Module 
(ECM) Replacement in this section. 
Did you complete the replacement? 

 

Go to Step 6 

 

6 

1.  Clear the DTCs with the scan tool. 
2.  Turn OFF the ignition for 30 seconds. 
3.  Start the engine. 
4.  Monitor the DTC Information with the scan tool. 
Did the DTC fail this ignition? 

 

Go to Step 3 

Go to Step 7 

7 

Observe the DTC Information with the scan tool. 
Are there any DTCs that you have not diagnosed? 

 

Go to Diagnostic 

Trouble Code (DTC) 

List System 

OK 

 

Engine Control System (4JH1)  6E-175 

DTC P0606 (Symptom Code A, B) (Flash Code 28) 

Description 
This diagnostic applies to internal microprocessor 
integrity conditions within the engine control module
(ECM). 
Condition for Running the DTC 
Symptom Code B 

•  The accelerator pedal position is less than 1%. 
•  The desired fuel injection quantity is 0 mg/strk. 

Condition for Setting the DTC 
Symptom Code A 

•  The ECM detects that the internal CPU does not

react. 

Symptom Code B 

•  The ECM detects that the engine speed is higher

than 2000 RPM. 

 

Action Taken When the DTC Sets 

•  The ECM illuminates the malfunction indicator 

lamp (MIL) when the diagnostic runs and fails. 

•  The ECM cuts fuel injection. 

Condition for Clearing the MIL/DTC 

•  The ECM turns OFF the MIL when the diagnostic 

runs and does not fail. 

•  A history DTC clears after 40 consecutive driving 

cycles without a fault. Or clear with the scan tool. 

 

DTC P0606 (Symptom Code A, B) (Flash Code 28) 
 

 

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 scan tool. 
2.  Turn OFF the ignition for 30 seconds. 
3.  Start the engine. 
4. Monitor the Diagnostic Trouble Code (DTC) 

Information with the scan tool. 

Does the DTC fail this ignition? 

 

Go to Step 3 

Go to Step 4 

3 

Important: Replacement ECM must be 
programmed. 
Replace the ECM. Refer to Engine Control Module 
(ECM) Replacement in this section. 
Did you complete the replacement? 

 

Go to Step 4 

 

4 

1.  Clear the DTCs with the scan tool. 
2.  Turn OFF the ignition for 30 seconds. 
3.  Start the engine. 
4.  Monitor the DTC Information with the scan tool. 
Did the DTC fail this ignition? 

 

Go to Step 3 

Go to Step 5 

5 

Observe the DTC Information with the scan tool. 
Are there any DTCs that you have not diagnosed? 

 

Go to Diagnostic 

Trouble Code (DTC) 

List System 

OK 

 
 

6E-176  Engine Control System (4JH1) 

DTC P0645 (Symptom Code 4) (Flash Code 46) 

Circuit Description 
The engine control module (ECM) controls the air 
conditioning (A/C) compressor relay, which supplies 
power to the A/C compressor clutch based on A/C
request input to the ECM from the heating, ventilation
and air conditioning (HVAC) controls. The ECM 
commands the A/C compressor relay ON at engine run. 
If the ECM detects an open circuit or short to ground on 
the A/C compressor relay control circuit, this DTC will
set. 
Condition for Running the DTC 

•  The ignition switch is ON.

 

•  The A/C compressor relay is once commanded

ON. 

Condition for Setting the DTC 

•  The ECM detects a low voltage condition on the

A/C compressor relay control circuit for longer than
3 seconds when the relay is commanded OFF. 

Action Taken When the DTC Sets 

•  The ECM illuminates the malfunction indicator

lamp (MIL) when the diagnostic runs and fails. 

 

Condition for Clearing the MIL/DTC 

•  The ECM turns OFF the MIL when the diagnostic 

runs and does not fail. 

•  A history DTC clears after 40 consecutive driving 

cycles without a fault. Or clear with the scan tool. 

Diagnostic Aids 

•  If an intermittent condition is suspected, refer to

Intermittent Conditions in this section. 

Notice:  

•  The A/C compressor relay is commanded OFF 

when the engine coolant temperature is reached 
around 105°C (221°F) and it commanded ON 
again below 100°C (212°F). 

 

DTC P0645 (Symptom Code 4) (Flash Code 46) 
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 scan tool. 
2.  Turn OFF the ignition for 30 seconds. 
3.  Turn ON the ignition, with the engine OFF. 
4.  Turn ON the blower motor switch and the A/C 

compressor switch. 

5.  Turn OFF the A/C compressor switch. 
6. Monitor the Diagnostic Trouble Code (DTC) 

Information with the scan tool. 

Does the DTC fail this ignition? 

 

Go to Step 3 

Go to Diagnostic 

Aids 

3 

1.  Turn OFF the ignition. 
2.  Replace the A/C compressor relay with the tail 

relay or replace with a known good relay. 

3.  Turn ON the ignition, with the engine OFF. 
4.  Turn ON the blower motor switch and the A/C 

compressor switch. 

5.  Turn OFF the A/C compressor switch. 
6.  Monitor the DTC Information with the scan tool. 
Does the DTC fail this ignition? 

 

Go to Step 4 

Go to Step 14 

4 

1.  Turn OFF the ignition. 
2.  Inspect the ECM (10A) fuse (EB-4) in the engine 

room fuse block. 

Is the ECM (10A) fuse (EB-4) open? 

 

Go to Step 5 

Go to Step 6 

5 

Replace the ECM (10A) fuse (EB-4). If the fuse 
continues to open, repair the short to ground on one 
of the circuits that is fed by the ECM (10A) fuse (EB-
4) or replace the shorted attached component fed by 
the ECM (10A) fuse (EB-4). 
Did you complete the repair? 

 

Go to Step 16 

 

Engine Control System (4JH1)  6E-177 

Step Action 

Value(s) 

Yes 

No 

6 

1.  Turn OFF the ignition. 
2.  Remove the A/C compressor relay. 
3.  Connect a test lamp between the voltage feed 

circuit of the A/C compressor relay coil side (pin 
3 of X-14 connector) and a known good ground. 

4.  Turn ON the ignition, with the engine OFF. 
Does the test lamp illuminate? 

 

Go to Step 7 

Go to Step 9 

7 

1.  Turn OFF the ignition. 
2. Connect a test lamp between the A/C 

compressor relay control circuit (pin 5 of X-14 
connector) and battery voltage. 

3.  Turn ON the ignition, with the engine OFF. 
Does the test lamp illuminate? 

 

Go to Step 10 

Go to Step 8 

8 

1.  Keep the test lamp with connected. 
2.  Start the engine. 
3.  Turn ON the blower motor switch and the A/C 

compressor switch. 

Does the test lamp illuminate when the A/C 
Compressor Relay parameter is ON? 

 

Go to Step 12 

Go to Step 11 

9 

Repair the open circuit or high resistance on the 
voltage feed circuit between the ECM (10A) fuse 
(EB-4) and the A/C compressor relay (pin 3 of X-14 
connector). 
Did you complete the repair? 

 

Go to Step 16 

 

10 

1.  Test the control circuit of the A/C compressor 

relay between the ECM (pin 41 of C-56 
connector) and the A/C compressor relay (pin 5 
of X-14 connector) for a short to ground. 

2.  Repair the circuit(s) as necessary. 
Did you find and correct the condition? 

 

Go to Step 16 

Go to Step 15 

11 

1.  Test the control circuit of the A/C compressor 

relay between the engine control module (ECM) 
(pin 41 of C-56 connector) and A/C compressor 
relay (pin 5 of X-14 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 16 

Go to Step 13 

12 

1.  Turn OFF the ignition. 
2. Inspect for an intermittent and for poor 

connections on the A/C compressor relay 
terminal (pins 3 and 5 of X-14 connector). 

3.  Repair the connection(s) as necessary. 
Did you find and correct the condition? 

 

Go to Step 16 

Go to Step 14 

13 

1.  Turn OFF the ignition. 
2.  Disconnect the ECM harness connector. 
3. Inspect for an intermittent and for a poor 

connection on the A/C compressor relay control 
circuit at the harness connector of the ECM (pin 
41 of C-56 connector). 

4.  Repair the connection (s) as necessary. 
Did you find and correct the condition? 

 

Go to Step 16 

Go to Step 15 

14 

Replace the A/C compressor relay. 
Did you complete the replacement? 

 

Go to Step 16 

