2007 ISUZU KB P190 Neutral switch

6E-62 Engine Control System (4JH1)
DTC
(Symptom Code) Flash
Code MIL
Status DTC Name on
scan tool Condition for
Running the DTC Condition for
Setting the DTC Possible Cause
P1173
(3) 22 OFF Limitation of
Injection Quantity •
The ignition switch
is ON. •
The ECM detects
an excessive high
coolant temperature
for longer than 30
seconds.
•
Engine overheat.
• Faulty engine cooling system.
• Faulty ECT sensor.

P1173 (7) 22 OFF Limitation of
Injection Quantity
•
The ignition switch
is ON. •
The ECM detects
an excessive high
FT for longer than
30 seconds.
•
Faulty PCU.


P1173 (A) 22 OFF Limitation of
Injection Quantity
•
The ignition switch
is ON. •
The ECM detects
an excessive low
FT for longer than
30 seconds.
•
Faulty PCU.

P1335 (A) 43 ON Crankshaft
Position (CKP)
Sensor Circuit •
The ignition switch
is ON. •
The PCU detects
CKP sensor signal
from the ECM is
faulty.
•
CKP sensor signal output circuit
is open circuit, high resistance,
short to ground, short to battery
or ignition voltage.
• Poor harness connector
connection.
• Faulty PCU.
• Faulty ECM.

P1345 (A) 41 ON Crankshaft
Position (CKP) –
Camshaft Position
(CMP) Correlation

•
The PCU received
faulty fuel injection
pump CMP sensor
signal for 1 second.
•
Faulty fuel injection pump.
• Faulty PCU.

P1520 (A) 47 ON Park/Neutral
Position Switch
Circuit •
The ignition switch
is ON.
• The engine speed
is higher than 1500
RPM.
• The vehicle speed
is higher than 63
km/h (39 MPH)
(M/T) or 78 km/h
(49 MPH) (A/T).
• The clutch pedal is
released. (M/T)
•
The ECM detects
that the neutral
switch signal is
continuously ON
(neutral or P/N
range) during three
consecutive driving
cycles.
•
Manual Transmission
• Neutral switch signal circuit is
short to battery or ignition
voltage.
• Faulty neutral switch.
• Faulty ECM.
• Automatic Transmission
• P & N position switch signal
circuit is short to battery or
ignition voltage.
• Misadjusted inhibitor switch.
• Faulty inhibitor switch.
• Faulty ECM.

P1520 (B) 47 ON Park/Neutral
Position Switch
Circuit •
The ignition switch
is ON.
• The engine speed
is higher than 665
RPM
• The vehicle speed
is lower than 2 km/h
(1.2 MPH).
• The clutch pedal is
released after once
depressed.
•
The ECM detects
that the neutral
switch signal is
continuously OFF
(other than neutral)
during three
consecutive driving
cycles.
•
ECM (10A) fuse (EB-4) open.
• Neutral switch ignition voltage
feed circuit is open circuit or high
resistance.
• Neutral switch signal circuit is
open circuit or high resistance.
• Poor harness connector
connection.
• Faulty neutral switch.
• Faulty ECM.

P1605 (C) 55 ON Control Module
Internal
Performance  •
The ECM detects
internal seed or key
file in EEPROM
data is destroyed.
•
Faulty ECM.

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ISUZU KB P190 2007

6E-210 Engine Control System (4JH1)
DTC P1520 (Symptom Code A) (Flash Code 47)
Circuit Description
(Manual Transmission)
The neutral switch is installed on the transmission gea
r
control box. W hen the gear position is neutral, the
switch is closed and the switch signal is provided to the
engine control module (ECM). If the ECM detects the
neutral switch signal is not changed from neutral during
the predetermined engine speed and vehicle speed
range, this DTC will set.
(Automatic Transmission)
The inhibitor switch is installed to the transmission case.
W hen the selector position is P or N range, the switch is
closed and the switch signal is provided to the Emir the
ECM detects the neutral switch signal is not changed
from P or N during the predetermined engine speed and
vehicle speed range, this DTC will set.
Condition for Running the DTC • The ignition switch is ON.
• The engine speed is higher than 1500 RPM.
• The vehicle speed is higher than 63 km/h (39
MPH) (M/T) or 78 km/h (49 MPH) (A/T).
• The clutch pedal is released. (M/T).

Condition for Setting the DTC
• The ECM detects that the neutral switch signal is
continuously ON (neutral or P/N range) during
three consecutive driving cycles.
Action Taken When the DTC Sets
• The ECM illuminates the malfunction indicato
r
lamp (MIL) when the diagnostic runs and fails.
Condition for Clearing the MIL/DTC
Important: • Following conditions must be met two consecutive
driving cycles. (One driving cycle: Ignition switch
ON > Engine run > Vehicle run > Ignition switch
OFF for 10 seconds)
- The engine speed is higher than 1500 RPM
- The vehicle speed is higher than 63 km/h (39 MPH) (M/T) or 78 km/h (49 MPH) (A/T)
- The clutch pedal is released (M/T)

- Other than neutral or P/N range
- After the above procedure is done, 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 P1520 (Symptom Code A) (Flash Code 47)
Schematic Reference: Engine Controls Schematics
Connector End View Reference: Engine Controls
Connector End Views or Engine Control Module (ECM)
Connector End Views

Chart for M/T
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. Observe the Neutral Switch parameter with the scan tool while shift to neutral and other
positions.
Does the scan tool indicate ON when the position is
neutral and OFF when other than the neutral? 

Go to Diagnostic Aids Go to Step 3
3 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.
Does the scan tool indicate ON? 

Go to Step 4 Go to Step 5
4 1. Test the neutral switch input 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 a short to battery or
ignition voltage.
2. Repair the circuit(s) as necessary.
Did you find and correct the condition? 

Go to Step 7 Go to Step 6

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ISUZU KB P190 2007

Engine Control System (4JH1) 6E-211
Step Action Value(s) Yes No
5 Replace the neutral switch. Refer to Neutral Switch
Replacement in Transmission Section.
Did you complete the replacement? 

Go to Step 7 
6 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 7 
7 1. Reconnect all previously disconnected harness
connector(s).
2. Clear the DTCs with the scan tool.
Important: Following conditions must be met two
consecutive driving cycles before clear with the scan
tool. (One driving cycle: Ignition switch ON > Engine
run > Vehicle run > Ignition switch OFF for 10
seconds) • The engine speed is higher than 1500 RPM
• The vehicle speed is higher than 63 km/h
(39 MPH)
• The clutch pedal is released
• Other than neutral
3. Turn ON the ignition, with the engine OFF.
4. Observe the Neutral Switch parameter with the scan tool while shift to neutral and other
positions.
Does the scan tool indicate ON when the position is
neutral and OFF when other than the neutral? 

Go to Step 8 Go to Step 3
8 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

Chart for A/T
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. Select the “JR405E Automatic Transmission” in the system selection menu.
5. Monitor the Read Diagnostic Trouble Code (DTC) Info As Stored By ECU with the scan tool.
Does the transmission control module (TCM) DTC
P0705 set? 

Go to Applicable
DTC in Automatic Transmission Section Go to Step 3
3 1. Install the scan tool. 2. Turn ON the ignition, with the engine OFF.
3. Observe the Neutral Switch parameter with the scan tool while shift to P or N and other
positions.
Does the scan tool indicate ON when the position is
P or N and OFF when other than the P or N? 

Go to Diagnostic Aids Go to Step 4

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ISUZU KB P190 2007

6E-212 Engine Control System (4JH1)
Step Action Value(s) Yes No
4 1. Check to ensure the inhibitor switch is adjusted
correctly.
2. Adjust the inhibitor switch as necessary. Refer to Inhibitor Switch Adjustment in Automatic
Transmission Section.
Did you find and correct the condition? 

Go to Step 7 Go to Step 5
5 1. Test the P & N position switch signal circuit between the engine control module (ECM) (pin
87 of C-57 connector) and the diode (pin 2 of X-
16 connector) for a short to battery or ignition
voltage.
2. Repair the circuit(s) as necessary.
Did you find and correct the condition? 

Go to Step 7 Go to Step 6
6 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 7 
7 1. Reconnect all previously disconnected harness
connector(s).
2. Clear the DTCs with the scan tool.
Important: Following conditions must be met two
consecutive driving cycles before clear with the scan
tool. (One driving cycle: Ignition switch ON > Engine
run > Vehicle run > Ignition switch OFF for 10
seconds) • The engine speed is higher than 1500 RPM
• The vehicle speed is higher than 78 km/h
(49 MPH)
• Other than P/N range
3. Turn ON the ignition, with the engine OFF.
4. Observe the Neutral Switch parameter with the scan tool while shift to P or N and other
positions.
Does the scan tool indicate ON when the position is
P or N and OFF when other than the P or N? 

Go to Step 8 Go to Step 2
8 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

Engine Control System (4JH1) 6E-213
DTC P1520 (Symptom Code B) (Flash Code 47)
Circuit Description
The neutral switch is installed on the transmission gea
r
control box. W hen the gear position is neutral, the
switch is closed and the switch signal is provided to the
engine control module (ECM). If the ECM detects the
neutral switch signal is not changed from other than
neutral during the predetermined engine speed and
vehicle speed range, this DTC will set. This DTC runs
only manual transmission.
Condition for Running the DTC

• The ignition switch is ON.
• The engine speed is higher than 665 RPM
• The vehicle speed is lower than 2 km/h (1.2 MPH).
• The clutch pedal is released after once depressed.
Condition for Setting the DTC • The ECM detects that the neutral switch signal is
continuously OFF (other than neutral) during three
consecutive driving cycles.
Action Taken When the DTC Sets • The ECM illuminates the malfunction indicato
r
lamp (MIL) when the diagnostic runs and fails.
Condition for Clearing the MIL/DTC
Important: • Following conditions must be met two consecutive
driving cycles. (One driving cycle: Ignition switch
ON > Engine run > Ignition switch OFF for 10
seconds)
- The engine speed is higher than 665 RPM
- The vehicle speed is lower than 2 km/h (1.2 MPH)
- The clutch pedal is released after once depressed
- Neutral position

- After the above procedure is done, 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 P1520 (Symptom Code B) (Flash Code 47)
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. Observe the Neutral Switch parameter with the scan tool while shift to neutral and other
positions.
Does the scan tool indicate ON when the position is
neutral and OFF when other than the neutral? 

Go to Diagnostic Aids Go to Step 3
3 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 4 Go to Step 5
4 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 13 

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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

Engine Control System (4JH1) 6E-215
Step Action Value(s) Yes No
13 1. Reconnect all previously disconnected harness
connector(s).
2. Clear the DTCs with the scan tool.
Important: Following conditions must be met two
consecutive driving cycles before clear with the scan
tool. (One driving cycle: Ignition switch ON > Engine
run > Ignition switch OFF for 10 seconds) • The engine speed is higher than 665 RPM
• The vehicle speed is lower than 2 km/h (1.2
MPH)
• The clutch pedal is released after once
depressed
• Neutral position
3. Turn ON the ignition, with the engine OFF.
4. Observe the Neutral Switch parameter with the scan tool while shift to neutral and other
positions.
Does the scan tool indicate ON when the position is
neutral and OFF when other than the neutral? 

Go to Step 14 Go to Step 3
14 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

ENGINE CONTROL SYSTEM (4JK1/4JJ1) 6E-25
Transmission Range Switch and Neutral Switch
RTW76EXF005001
E-51
H-5
E-51
Transmission
range
switch
3
2
8 NP
X-16
X-16 C-94 C-95
TCM
Diode
4
2
3 0.75
WHT
0.5
RED/
BLK
0.5
RED/
BLK
0.5
RED/
BLK 0.5
YEL/
VIO
0.5
YEL/
VIO
0.5
YEL/
VIO 0.5
YEL/
VIO 0.5
RED/
BLK
0.5
RED/
GRN
9
2
10
2 Neutral
switch
M/T
Standard output
A/T
0.5
BLK/
WHT Reverse
lamp
switch
0.5
BLK/
WHT
0.85
WHT
0.85
WHT
0.75
WHT
1 E-11
13 H-4 1 E-12 0.85
WHT
3 H-4
3 H-4 E-51
H-5
E-51
Transmission
range
switch
4
5
6 NP
X-16
X-16 C-95
TCM
Diode
4
2
3 0.75
WHT
0.5
RED/
BLK
0.5
RED/
BLK
0.5
RED/
BLK 0.5
YEL/
VIO
0.5
YEL/
VIO
0.5
YEL/
VIO 0.5
YEL/
VIO 0.5
RED/
BLK
0.5
RED/
GRN
9
2
8
20 Neutral
switch
M/T
High output
A/T
0.5
BLK/
WHT
0.5
BLK/
WHT
0.85
WHT
0.75
WHT
2 E-111
13 H-4 1 E-111
C-10
Back up
15A
Fuse/
relay
box
(Cabin)
3 C-58 ECM
PorN
range/
Neutral
switch
signal

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ISUZU KB P190 2007