2007 ISUZU KB P190 engine

TRANSMISSION CONTROL SYSTEM (JR405E) 7A2-67
DTC P0768 (Flash Code 34)
Circuit Description
The low clutch solenoid valve controls fluid acting on
spool valves in the low clutch hydraulic circuits, which
then controls low clutch apply and release. The
solenoid valve is installed to the lower part of the valve
body assembly. The TCM controls the solenoid valve
by a duty cycle (pulse width modulation [PWM]) signal
based on the commanded gear position. The solenoid
valve provides a smooth gearshift by operating on a
duty cycle percentage of ON time. The TCM monitors
the low clutch solenoid valve operating status through
the feedback circuit. If the TCM detects an improper
voltage level on the control circuit, this DTC will set.
Condition for Running the DTC • The ignition switch is ON.
Condition for Setting the DTC • The TCM detects an open circuit or short circuit on the low clutch solenoid valve control circuit.
Action Taken When the DTC Sets • The TCM blinks the Check Trans lamp when the diagnostic runs and fails.
During the vehicle running;
• The TCM holds the last gear position when the diagnostic runs and fails.
• The TCM stops low clutch solenoid valve. • The TCM inhibits lock up control.
After the vehicle stopped;
• The TCM stops all shift solenoid valves and fixes to the 3rd gear. If a fail-safe valve problem is
detected, the shift solenoid valves are not stopped
but gear is fixed to the 3rd gear.
• The TCM stops PC solenoid valve.
Condition for Clearing the DTC • The TCM turns OFF the Check Trans lamp when the diagnostic runs and does not fail at next
ignition cycle.
• A current DTC clears when the diagnostic runs and does not fail at next ignition cycle.
Diagnostic Aids • If an intermittent condition is suspected, refer to Intermittent Conditions in this section.
• Use the Clutch, Brake, Solenoid and Pressure Switch Logic table to verify each component works
properly within the selected gear range.
Schematic Reference: Transmission Controls
Schematics
Connector End View Reference: Transmission
Controls Connector End Views or TCM Connector End
Views
Circuit/ System Testing DTC P0768
Step Action Value(s)Yes No
1 Did you perform the Diagnostic System Check -
Transmission Controls? —
Go to Step 2 Go to Diagnostic
System Check - Transmission Controls
2 1. Install a scan tool.
2. Turn OFF the ignition for 30 seconds.
3. Lift the driving wheels or drive the vehicle while observing the DTC Information with a
scan tool.
Is DTC P1875 also set? —
Go to DTC P1875 Go to Step 3
3 1. Park the vehicle.
2. Turn ON the ignition, with the engine OFF.
3. Perform the Low Clutch Solenoid control with a scan tool.
4. Command the solenoid valve ON and OFF.
Does the low clutch solenoid valve click with each
command? —
Go to Diagnostic Aids Go to Step 4

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ISUZU KB P190 2007

7A2-68 TRANSMISSION CONTROL SYSTEM (JR405E)
41. Turn OFF the ignition.
2. Disconnect the in-line harness connector (E- 54) near the transmission range switch.
3. Connect a test lamp between the control circuit (pin 3 of E-54 female side) and a known
good ground.
4. Turn ON the ignition, with the engine OFF.
5. Perform the Low Clutch Solenoid control with a scan tool.
6. Command the solenoid valve ON and OFF.
Does the test lamp turn ON and OFF with each
command? —
Go to Step 9 Go to Step 5
5 Does the test lamp remain illuminated with each
command? —
Go to Step 6 Go to Step 7
6 1. Test the control circuit between the TCM (pin 9
of C-95) and the in-line harness connector (pin
3 of E-54 female side) 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 13 Go to Step 12
7 1. Test the control circuit between the TCM (pin 9
of C-95) and the in-line harness connector (pin
3 of E-54 female side) for the following
conditions:
• An open circuit
• A short to ground
• High resistance
2. Repair the circuit(s) as necessary.
Did you find and correct the condition? —
Go to Step 13 Go to Step 8
8 1. Turn OFF the ignition.
2. Disconnect the TCM harness connector.
3. Inspect for an intermittent and for a poor connection at the harness connector of the
TCM (pin 9 of C-95).
4. Repair the connection(s) as necessary.
Did you find and correct the condition? —
Go to Step 13 Go to Step 12
9 1. Inspect for an intermittent and for a poor
connection at the in-line harness connector
(pin 3 of E-54).
2. Repair the connection(s) as necessary.
Did you find and correct the condition? —
Go to Step 13 Go to Step 10
Step
Action Value(s)Yes No

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ISUZU KB P190 2007

TRANSMISSION CONTROL SYSTEM (JR405E) 7A2-69
101. Remove the transmission oil pan. Refer to
repair instructions (On-Vehicle Service).
2. Inspect the low clutch solenoid valve for the following conditions:
• Physical damage of solenoid valve
• Loose or improper installation of solenoid valve
3. Inspect for an intermittent and for a poor connection at the harness connector of the
low clutch solenoid valve or in-line harness
connector.
4. Inspect for an intermittent and for a poor connection of ground wire.
5. Test the control circuit between the low clutch solenoid valve and the in-line harness
connector (pin 3 of E-54 male side) for the
following conditions:
• An open circuit
• A short to ground
• A short to the other solenoid valve circuit
• High resistance
6. Repair the connection(s) or circuit(s) as necessary.
Did you find and correct the condition? —
Go to Step 13 Go to Step 11
11 Replace the low clutch solenoid valve. Refer to
repair instructions (On-Vehicle Service).
Did you complete the replacement? —
Go to Step 13 —
12 Important:
Replacement TCM must be
programmed.
Replace the TCM. Refer to TCM Replacement.
Did you complete the replacement? —
Go to Step 13 —
13 1. Reconnect all previously disconnected
components or harness connector(s).
2. Clear the DTCs with a scan tool.
3. Turn OFF the ignition for 30 seconds.
4. Start the engine.
5. Lift the driving wheels or drive the vehicle while observing the DTC Information with a
scan tool.
Did the DTC fail this ignition? —
Go to Step 4 Go to Step 14
14 Observe the DTC Information with a scan tool.
Are there any DTCs that you have not diagnosed? —
Go to DTC List System OK
Step
Action Value(s)Yes No

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ISUZU KB P190 2007

7A2-70 TRANSMISSION CONTROL SYSTEM (JR405E)
DTC P1120 (Flash Code 22)
Circuit Description
The accelerator pedal position (APP) sensor is
mounted on the accelerator pedal control assembly.
The analogue APP signals are converted by the engine
control module (ECM) into a pulse width modulation
(PWM) signal. This converted signal is continually sent
from the ECM to the TCM to determine appropriate
shift points depending on the accelerator pedal
pressing amount. If the TCM fails to receive a PWM
signal from the ECM, this DTC will set.
Condition for Running the DTC • The ignition switch is ON.
Condition for Setting the DTC • The TCM detects that the APP PWM signal from the ECM is not being received.
Action Taken When the DTC Sets • The TCM blinks the Check Trans lamp when the diagnostic runs and fails.
During the vehicle running; • The TCM holds the last gear position when the
diagnostic runs and fails.
• The TCM inhibits lock up control.
After the vehicle stopped;
• The TCM stops all shift solenoid valves and fixes to the 3rd gear. If a fail-safe valve problem is
detected, the shift solenoid valves are not stopped
but gear is fixed to the 3rd gear.
• The TCM stops PC solenoid valve.
Condition for Clearing the DTC • The TCM turns OFF the Check Trans lamp when the diagnostic runs and does not fail.
• A current DTC clears when the diagnostic runs and does not fail.
Diagnostic Aids • If an intermittent condition is suspected, refer to Intermittent Conditions in this section.
Circuit/ System Testing DTC P1120
Step Action Value(s)Yes No
1 Did you perform the Diagnostic System Check -
Transmission Controls? —
Go to Step 2 Go to Diagnostic
System Check - Transmission
Controls
2 1. Install a scan tool.
2. Turn OFF the ignition for 30 seconds.
3. Start the engine.
4. Monitor the ENGINE DTC Information with a scan tool.
Is DTC P2621 or P2622 set? —
Go to Applicable DTC in engine
control section Go to Diagnostic
Aids

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ISUZU KB P190 2007

7A2-72 TRANSMISSION CONTROL SYSTEM (JR405E)
41. Remove the transmission oil pan. Refer to
repair instructions (On-Vehicle Service).
2. Inspect the low & reverse brake solenoid valve and transmission fluid pressure (TFP) switch
for the following conditions:
• Physical damage
• Loose or improper installation
3. Test the signal circuit between the low & reverse brake TFP switch and the in-line
harness connector (pin 12 of E-54 male side)
for a short to ground.
4. Repair the circuit(s) or replace as necessary.
Did you find and correct the condition? —
Go to Step 7 Go to Step 5
5 1. Remove the low & reverse brake solenoid
valve and TFP switch from the valve body
assembly and perform function check. Refer
to repair instructions (On-Vehicle Service).
2. Repair or replace as necessary.
Did you find and correct the condition? —
Go to Step 7 Go to Step 6
6 Repair or replace the valve body assembly. Refer
to repair instructions (On-Vehicle Service or Unit
Repair).
Did you complete the repair or replacement? —
Go to Step 7 —
7 1. Reconnect all previously disconnected
components or harness connector(s).
2. Clear the DTCs with a scan tool.
3. Turn OFF the ignition for 30 seconds.
4. Start the engine.
5. Drive the vehicle while observing the DTC Information with a scan tool.
Did the DTC fail this ignition? —
Go to Step 2 Go to Step 8
8 Observe the DTC Information with a scan tool.
Are there any DTCs that you have not diagnosed? —
Go to DTC List System OK
Step
Action Value(s)Yes No

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ISUZU KB P190 2007

7A2-74 TRANSMISSION CONTROL SYSTEM (JR405E)
41. Remove the transmission oil pan. Refer to
repair instructions (On-Vehicle Service).
2. Inspect the 2-4 brake solenoid valve and transmission fluid pressure (TFP) switch for
the following conditions:
• Physical damage
• Loose or improper installation
3. Test the signal circuit between the 2-4 brake TFP switch and the in-line harness connector
(pin 7 of E-54 male side) for a short to ground
4. Repair the circuit(s) or replace as necessary.
Did you find and correct the condition? —
Go to Step 7 Go to Step 5
5 1. Remove the 2-4 brake solenoid valve and TFP
switch from the valve body assembly and
perform function check. Refer to repair
instructions (On-Vehicle Service).
2. Repair or replace as necessary.
Did you find and correct the condition? —
Go to Step 7 Go to Step 6
6 Repair or replace the valve body assembly. Refer
to repair instructions (On-Vehicle Service or Unit
Repair).
Did you complete the repair or replacement? —
Go to Step 7 —
7 1. Reconnect all previously disconnected
components or harness connector(s).
2. Clear the DTCs with a scan tool.
3. Turn OFF the ignition for 30 seconds.
4. Start the engine.
5. Drive the vehicle while observing the DTC Information with a scan tool.
Did the DTC fail this ignition? —
Go to Step 2 Go to Step 8
8 Observe the DTC Information with a scan tool.
Are there any DTCs that you have not diagnosed? —
Go to DTC List System OK
Step
Action Value(s)Yes No

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ISUZU KB P190 2007

TRANSMISSION CONTROL SYSTEM (JR405E) 7A2-75
DTC P1853 (Flash Code 26)
Circuit Description
The low & reverse brake transmission fluid pressure
(TFP) switch is installed to the lower part of the valve
body assembly and it feedbacks fluid pressure in the
low & reverse brake hydraulic circuit. When the
solenoid valve is energized, fluid pressure is drained to
disengage the low & reverse brake and the TFP switch
is OFF. When the solenoid valve is not energized, fluid
pressure is applied to engage the low & reverse brake
and the TFP switch is ON. The TCM monitors the low &
reverse brake TFP switch ON/ OFF status through the
signal circuit. If the TCM detects an improper status on
the signal circuit, this DTC will set.
Condition for Running the DTC • DTCs P0560, P0705, P0717, P0722, P0753, P0758, P0763, P0768, P1120, P1750, P1755 and
P1875 are not set.
AND following conditions are met for longer than 2.5
seconds.
• The ignition switch is ON.
• The transmission fluid temperature is more than 60 °C (140 °F).
• The engine speed is more than 500 RPM.
• The TCM is not under gearshift control.
Condition for Setting the DTC
Either of following condition is met: • The TCM detects that the low & reverse brake TFP switch signal is stuck at the ON for longer than 2
seconds when the selector lever in D range with
4th gear. • The TCM detects that the low & reverse brake TFP
switch signal is stuck at the OFF for longer than 2
second when the selector lever in R range.
Action Taken When the DTC Sets • The TCM blinks the Check Trans lamp when the diagnostic runs and fails.
Condition for Clearing the DTC • The TCM turns OFF the Check Trans lamp when the diagnostic runs and does not fail.
• A current DTC clears when the diagnostic runs and does not fail.
Diagnostic Aids • If an intermittent condition is suspected, refer to Intermittent Conditions in this section.
• Use the Clutch, Brake, Solenoid and Pressure Switch Logic table to verify each component works
properly within the selected gear range.
• A sticking or intermittently sticking the low & reverse brake solenoid valve will cause this DTC to
set.
Schematic Reference: Transmission Controls
Schematics
Connector End View Reference: Transmission
Controls Connector End Views or TCM Connector End
Views
Circuit/ System Testing DTC P1853
Step Action Value(s)Yes No
1 Did you perform the Diagnostic System Check -
Transmission Controls? —
Go to Step 2 Go to Diagnostic
System Check -
Transmission Controls
2 1. Install a scan tool.
2. Turn OFF the ignition for 30 seconds.
3. Lift the driving wheels or drive the vehicle while observing the DTC Information with a
scan tool.
Is DTC P0753 also set? —
Go to DTC P0753 Go to Step 3
3 Place the selector lever in forward range while
observing the Low & Reverse Brake Pressure
Switch parameter with a scan tool.
Does the Low & Reverse Brake Pressure Switch
parameter ever indicate ON when gear is shifted
between 1st and 4th? —
Go to Step 5 Go to Step 4

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ISUZU KB P190 2007

7A2-76 TRANSMISSION CONTROL SYSTEM (JR405E)
4Place the selector lever in R range while observing
the Low & Reverse Brake Pressure Switch
parameter with a scan tool.
Does the Low & Reverse Brake Pressure Switch
parameter indicate ON? —
Go to Diagnostic Aids Go to Step 5
5 1. Turn OFF the ignition.
2. Disconnect the in-line harness connector (E- 54) near the transmission range switch.
3. Turn ON the ignition, with the engine OFF.
4. Observe the Low & Reverse Brake Switch parameter with a scan tool while momentarily
jumping 3-amp fused jumper wire between pin
12 of E-54 (female side) and a known good
ground.
Does the scan tool indicate ON when the circuit is
jumpered and OFF when the circuit is not
jumpered? —
Go to Step 8 Go to Step 6
6 1. Test the signal circuit between the TCM (pin
12 of C-95) and the in-line harness connector
(pin 12 of E-54 female side) for the following
conditions:
• An open circuit
• A short to ground
• High resistance
2. Repair the circuit(s) as necessary.
Did you find and correct the condition? —
Go to Step 13 Go to Step 7
7 1. Turn OFF the ignition.
2. Disconnect the TCM harness connector.
3. Inspect for an intermittent and for a poor connection at the harness connector of the
TCM (pin 12 of C-95).
4. Repair the connection(s) as necessary.
Did you find and correct the condition? —
Go to Step 13 Go to Step 12
8 1. Inspect for an intermittent and for a poor
connection at the in-line harness connector
(pin 12 of E-54).
2. Repair the connection(s) as necessary.
Did you find and correct the condition? —
Go to Step 13 Go to Step 9
Step
Action Value(s)Yes No

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ISUZU KB P190 2007