2007 ISUZU KB P190 air condition

6E-214 Engine Control System (4JH1)
Step Action Value(s) Yes No
5 1. Turn OFF the ignition.
2. Disconnect the neutral switch harness connector.
3. Turn ON the ignition, with the engine OFF.
4. Observe the Neutral Switch parameter with the scan tool while momentarily jumping across the
neutral switch harness connectors between pin 1
of E-11 connector and pin 1 of E-12 connector.
Does the scan tool indicate ON when the circuit is
jumped and OFF when the circuit is not jumped? 

Go to Step 9 Go to Step 6
6 1. Connect a test lamp between the ignition voltage feed circuit of the neutral switch harness (pin 1 of
E-12 connector) and a known good ground.
2. Turn ON the ignition, with the engine OFF.
Does the test lamp illuminate? 

Go to Step 8 Go to Step 7
7 Repair the open circuit or high resistance on the ignition voltage feed circuit between the ECM (10A)
fuse (EB-4) and the neutral switch (pin 1 of E-12
connector).
Did you complete the repair? 

Go to Step 13 
8 1. Test the neutral switch signal circuit between the
engine control module (ECM) (pin 87 of C-57
connector) and the neutral switch (pin 1 of E-11
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 13 Go to Step 10
9 1. Turn OFF the ignition. 2. Inspect for an intermittent and for poor connections at the harness connectors of the
neutral switch (pin 1 of E-11 connector and pin 1
of E-12 connector).
3. Repair the connection(s) as necessary.
Did you find and correct the condition? 

Go to Step 13 Go to Step 11
10 1. Turn OFF the ignition. 2. Disconnect the ECM harness connector.
3. Inspect for an intermittent and for a poor connection on the neutral switch circuit at the
harness connector of the ECM (pin 87 of C-57
connector).
4. Repair the connection(s) as necessary.
Did you find and correct the condition? 

Go to Step 13 Go to Step 12
11 Replace the neutral switch. Refer to Neutral Switch Replacement in Transmission Section.
Did you complete the replacement? 

Go to Step 13 
12 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 13 

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ISUZU KB P190 2007

6E-222 Engine Control System (4JH1)
DTC P1625 (Symptom Code A) (Flash Code 76)
Circuit Description
The engine control module (ECM) main relay is
energized when the ECM receives an ignition voltage
switch ON signal. W hen the ignition switch is OFF, the
ECM main relay is de-energized after a certain length o
f
time passed. If the ECM detects the ECM main relay is
turned OFF before ECM commanded OFF, this DTC
will set.
Condition for Setting the DTC
• The ECM detects that the ECM main relay is
turned OFF before commanded turned OFF.
Action Taken When the DTC Sets • The ECM does not illuminate the malfunction
indicator lamp (MIL) when the diagnostic runs and
fails.
Condition for Clearing the DTC
• 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.
• Faulty ECM main relay may set this DTC.

DTC P1625 (Symptom Code A) (Flash Code 76)
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. Monitor the Diagnostic Trouble Code (DTC) Information with the scan tool.
5. Turn OFF the ignition.
6. Turn ON the ignition, with the engine OFF.
Does the DTC fail this ignition? 

Go to Step 3 Go to Diagnostic
Aids
3 1. Turn OFF the ignition. 2. Disconnect the ECM main relay.
3. Inspect for an intermittent, for poor connections and corrosion at the harness connector of the
ECM main relay (pins 1, 2, 4 and 5 of X-12
connector).
4. Disconnect the engine control module (ECM) harness connector.
5. Inspect for an intermittent, for poor connections and corrosion on ECM main relay control and
battery voltage feed circuit at the harness
connector of the ECM (pins 3 and 58 of C-56
connector).
6. Test for high resistance on each ECM main relay circuit.
7. Repair the connection(s) or circuit(s) as necessary.
Did you find and correct the condition? 

Go to Step 5 Go to Step 4
4 Replace the ECM main relay. Did you complete the replacement? 

Go to Step 5 

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ISUZU KB P190 2007

6E-224 Engine Control System (4JH1)
DTC P1625 (Symptom Code B) (Flash Code 76)
Circuit Description
The engine control module (ECM) main relay is
energized when the ECM receives an ignition voltage
switch ON signal. W hen the ignition switch is OFF, the
ECM main relay is de-energized after a certain length o
f
time passed. If the ECM detects the ECM main relay
has been ON since the ignition switch was turned OFF,
this DTC will set.
Condition for Running the DTC
• The ignition switch is OFF.
Condition for Setting the DTC • The ECM detects that the ECM main relay is
turned ON for longer than 2 seconds.
Action Taken When the DTC Sets • The ECM does not illuminate the malfunction
indicator lamp (MIL) when the diagnostic runs and
fails.
Condition for Clearing the DTC
• 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.
• Faulty or sticking ECM main relay may set this
DTC.
Test Description
The numbers below refer to the step number on the
diagnostic table.
2. If this DTC is present, scan tool can communicate
with the ECM when the ignition switch is OFF.

DTC P1625 (Symptom Code B) (Flash Code 76)
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. Monitor the Diagnostic Trouble Code (DTC) Information with the scan tool.
Does the DTC fail with the ignition switch OFF? 

Go to Step 3 Go to Diagnostic
Aids
3 1. Disconnect the ECM main relay. 2. Monitor the DTC Information with the scan tool.
Does the DTC fail with the ignition switch OFF? 

Go to Step 6 Go to Step 4
4 1. Turn OFF the ignition. 2. Disconnect the ECM main relay.
3. Connect a test lamp between the control circuit of the ECM main relay harness (pin 4 of X-12
connector) and battery voltage.
4. Keep the ignition switch OFF.
Does the test lamp illuminate? 

Go to Step 5 Go to Step 7
5 1. Test the control circuit of the ECM main relay between the engine control module (ECM) (pin
58 of C-56 connector) and the ECM main relay
(pin 4 of X-12 connector) for a short to ground.
2. Repair the circuit(s) as necessary.
Did you find and correct the condition? 

Go to Step 9 Go to Step 8
6 Repair the short to battery on the voltage feed supply circuit to the ECM between the ECM (pin 3 of
C-56 connector) and the ECM main relay (pin 1 of X-
12 connector).
Did you complete the repair? 

Go to Step 9 
7 Replace the ECM main relay.
Did you complete the replacement? 

Go to Step 9 

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ISUZU KB P190 2007

6E-228 Engine Control System (4JH1)
Step Action Value(s) Yes No
7 1. Turn OFF the ignition.
2. Reconnect the PCU harness connector.
3. Disconnect the engine control module (ECM) C- 57 harness connector. Keep the ECM C-56
harness connector with connected.
4. Connect a DMM across the CAN harness (pins 99 and 100 of C-57 connector).
5. Measure the resistance across the CAN terminals.
Is the resistance within the specified value? 110-130
Ω
Go to Step 8 Go to Step 14
8 1. Connect a DMM between the CAN Low signal circuit of the ECM harness (pin 99 of C-57
connector) and a known good ground.
2. Turn ON the ignition, with the engine OFF.
Is the DMM voltage within the specified value? 1.5 – 2.5 volts
Go to Step 9 Go to Step 16
9 1. Keep the ignition switch ON, with the engine OFF.
2. Connect a DMM between the CAN High signal circuit of the ECM harness (pin 100 of C-57
connector) and a known good ground.
Is the DMM voltage within the specified value? 3.0 – 4.0 volts
Go to Step 13 Go to Step 16
10 1. Test the CAN Low and High circuit between the ECM (pins 99 and 100 of C-57 connector) and
the PCU (pins 1 and 2 of E-6 connector) for the
following conditions: • An open circuit
• A short each other
• High resistance.
2. Repair the circuit(s) as necessary.
Did you find and correct the condition? 

Go to Step 18 Go to Step 15
11 1. Test the CAN Low circuit between the ECM (pin 99 of C-57 connector) and the PCU (pin 1 of E-9
connector) for the following conditions: • A short to ground
• A short to battery or ignition voltage
2. Repair the circuit(s) as necessary.
Did you find and correct the condition? 

Go to Step 18 Go to Step 17
12 1. Test the CAN Low circuit between the ECM (pin 100 of C-57 connector) and the PCU (pin 2 of E-
9 connector) for the following conditions: • A short to ground
• A short to battery or ignition voltage
2. Repair the circuit(s) as necessary.
Did you find and correct the condition? 

Go to Step 18 Go to Step 17
13 1. Reconnect all previously disconnected harness connector(s).
2. Clear the DTCs with the scan tool.
3. Turn OFF the ignition for 30 seconds.
4. Turn ON the ignition, with the engine OFF.
5. Monitor the DTC Information with the scan tool.
Is DTC P0251 (Symptom Code E) set? 

Go to Step 16 Go to Diagnostic
Aids

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ISUZU KB P190 2007

Engine Control System (4JH1) 6E-229
Step Action Value(s) Yes No
14 1. Turn OFF the ignition.
2. Disconnect the PCU harness connector.
3. Inspect for an intermittent and for poor connections at the harness connector of the PCU
(pins 1 and 2 of E-6 connector).
4. Repair the connection(s) as necessary.
Did you find and correct the condition? 

Go to Step 18 Go to Step 16
15 1. Turn OFF the ignition. 2. Disconnect the ECM harness connector.
3. Inspect for an intermittent and for poor connections on the CAN Low or High circuits at
the harness connector of the ECM (pins 99 and
100 of C-57 connector).
4. Repair the connection(s) as necessary.
Did you find and correct the condition? 

Go to Step 18 Go to Step 17
16 Important: The fuel injection pump must be timed to
the engine.
Replace the fuel injection pump. Refer to Fuel
Injection Pump Replacement in engine mechanical
section. (PCU is part of the fuel injection pump
assembly)
Did you complete the replacement? 

Go to Step 18 
17 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 18 
18 1. Reconnect all previously disconnected harness
connector(s).
2. Clear the DTCs with the scan tool.
3. Turn OFF the ignition for 30 seconds.
4. Start the engine.
5. Monitor the DTC Information with the scan tool.
Does the DTC fail this ignition? 

Go to Step 2 Go to Step 19
19 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


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ISUZU KB P190 2007

6E-232 Engine Control System (4JH1)
Step Action Value(s) Yes No
6 1. Turn OFF the ignition.
2. Reconnect the PCU harness connector.
3. Disconnect the engine control module (ECM) C- 57 harness connector. Keep the ECM C-56
harness connector with connected.
4. Connect a DMM across the CAN harness pins 99 and 100 of C-57 connector).
5. Measure the resistance across the CAN terminals.
Is the resistance within the specified value? 110-130
Ω
Go to Step 7 Go to Step 13
7 1. Connect a DMM between the CAN Low signal circuit of the ECM harness (pin 99 of C-57
connector) and a known good ground.
2. Turn ON the ignition, with the engine OFF.
Is the DMM voltage within the specified value? 1.5 – 2.5 volts
Go to Step 8 Go to Step 15
8 1. Keep the ignition switch ON, with the engine OFF.
2. Connect a DMM between the CAN High signal circuit of the ECM harness (pin 100 of C-57
connector) and a known good ground.
Is the DMM voltage within the specified value? 3.0 – 4.0 volts
Go to Step 12 Go to Step 15
9 1. Test the CAN Low and High circuit between the ECM (pins 99 and 100 of C-57 connector) and
the PCU (pins 1 and 2 of E-6 connector) for the
following conditions: • An open circuit
• A short each other
• High resistance
2. Repair the circuit(s) as necessary.
Did you find and correct the condition? 

Go to Step 17 Go to Step 14
10 1. Test the CAN Low circuit between the ECM (pin 99 of C-57 connector) and the PCU (pin 1 of E-9
connector) for the following conditions: • A short to ground
• A short to battery or ignition voltage
2. Repair the circuit(s) as necessary.
Did you find and correct the condition? 

Go to Step 17 Go to Step 16
11 1. Test the CAN Low circuit between the ECM (pin 100 of C-57 connector) and the PCU (pin 2 of E-
9 connector) for the following conditions: • A short to ground
• A short to battery or ignition voltage
2. Repair the circuit(s) as necessary.
Did you find and correct the condition? 

Go to Step 17 Go to Step 16
12 1. Reconnect all previously disconnected harness connector(s).
2. Clear the DTCs with the scan tool.
3. Turn OFF the ignition for 30 seconds.
4. Turn ON the ignition, with the engine OFF.
5. Monitor the DTC Information with the scan tool.
Is DTC P0251 (Symptom Code E) set? 

Go to Step 15 Go to Diagnostic
Aids

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ISUZU KB P190 2007

Engine Control System (4JH1) 6E-233
Step Action Value(s) Yes No
13 1. Turn OFF the ignition.
2. Disconnect the PCU harness connector.
3. Inspect for an intermittent and for poor connections at the harness connector of the PCU
(pins 1 and 2 of E-6 connector).
4. Repair the connection(s) as necessary.
Did you find and correct the condition? 

Go to Step 17 Go to Step 15
14 1. Turn OFF the ignition. 2. Disconnect the ECM harness connector.
3. Inspect for an intermittent and for poor connections on the CAN Low or High circuits at
the harness connector of the ECM (pins 99 and
100 of C-57 connector).
4. Repair the connection(s) as necessary.
Did you find and correct the condition? 

Go to Step 17 Go to Step 16
15 Important: The fuel injection pump must be timed to
the engine.
Replace the fuel injection pump. Refer to Fuel
Injection Pump Replacement in engine mechanical
section. (PCU is part of the fuel injection pump
assembly)
Did you complete the replacement? 

Go to Step 17 
16 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 17 
17 1. Reconnect all previously disconnected harness
connector(s).
2. Clear the DTCs with the scan tool.
3. Turn OFF the ignition for 30 seconds.
4. Start the engine.
5. Monitor the DTC Information with the scan tool.
Does the DTC fail this ignition? 

Go to Step 3 Go to Step 18
18 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


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ISUZU KB P190 2007

6E-234 Engine Control System (4JH1)
DTC P1690 (Symptom Code 4) (Flash Code 77)
Circuit Description
The malfunction indicator lamp (MIL) is located on the
instrument panel cluster (IPC). The battery voltage is
supplied to the MIL. The engine control module (ECM)
turns the MIL ON by grounding the MIL control circuit.
After a fixed time passes, the ECM turns OFF the MIL
with the ignition ON and the engine OFF. The MIL has
the following functions:
• The MIL informs the driver that a malfunction has
occurred and the vehicle should be taken in fo
r
service as soon as possible.
• The MIL illuminates during a bulb test and a
system test.
•
A DTC will be stored if a MIL is requested by the
ECM.
If the ECM detects an open circuit or short circuit on the
MIL control circuit, this DTC will set.
Condition for Running the DTC • The ignition switch is ON.
Condition for Setting the DTC

• The ECM detects a low voltage condition on the
MIL control circuit for longer than 3 seconds when
the MIL is commanded OFF.
Action Taken When the DTC Sets • The ECM does not illuminates the MIL when the
diagnostic runs and fails.
Condition for Clearing the DTC • 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.

DTC P1690 (Symptom Code 4) (Flash Code 77)
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 ON the ignition, with the engine OFF.
3. Perform the Malfunction Indicator Lamp (MIL) test with the scan tool.
4. Command the MIL ON with the scan tool.
Does the MIL turn ON when commanded ON with
the scan tool? 

Go to Step 3 Go to Step 4
3 Command the MIL OFF with the scan tool. Does the MIL OFF? 

Go to Step 17 Go to Step 10
4 1. Turn OFF the ignition.
2. Inspect the Meter (15A) fuse (C-14) in the cabin fuse block.
Is the Meter (15A) fuse (C-14) open? 

Go to Step 5 Go to Step 6
5 Replace the Meter (15A) fuse (C-14). If the fuse continues to open, repair the short to ground on one
of the circuits that fed by the Meter (15A) fuse (C-14)
or replace the shorted attached component fed by
the Meter (15A) fuse (C-14).
Did you complete the repair? 

Go to Step 19 
6 1. Turn OFF the ignition.
2. Disconnect the engine control module (ECM) harness connector.
3. Turn ON the ignition, with the engine OFF.
4. Connect a 3-amp fused jumper wire between the MIL control circuit of the ECM harness connector
(pin 42 of C-56 connector) and a known good
ground.
Does the MIL illuminate? 

Go to Step 11 Go to Step 7

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ISUZU KB P190 2007