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TRANSMISSION CONTROL SYSTEM (JR405E) 7A2-85
4Place the selector lever in P, R and N range while
observing the High Clutch Pressure Switch
parameter with a scan tool.
Does the High Clutch Pressure Switch parameter
indicate OFF? —
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 high clutch Switch parameter with a scan tool while momentarily jumping 3-
amp fused jumper wire between pin 1 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
20 of C-95) and the in-line harness connector
(pin 1 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 20 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 1 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
Page 4370 of 6020

7A2-86 TRANSMISSION CONTROL SYSTEM (JR405E)
91. Remove the transmission oil pan. Refer to
repair instructions (On-Vehicle Service).
2. Inspect the high clutch solenoid valve and transmission fluid pressure (TFP) switch for
the following conditions:
• Physical damage
• Loose or improper installation
3. Inspect for an intermittent and for a poor connection at the harness connector of the
high clutch TFP switch or in-line harness
connector.
4. Test the signal circuit between the high clutch TFP switch and the in-line harness connector
(pin 1 of E-54 male side) for the following
conditions:
• An open circuit
• A short to ground
• A short to the solenoid valve circuit
• High resistance
5. Repair the connection(s), circuit(s) or replace as necessary.
Did you find and correct the condition? —
Go to Step 13 Go to Step 10
10 1. Remove the high clutch 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 13 Go to Step 11
11 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 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. 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 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
Page 4371 of 6020

TRANSMISSION CONTROL SYSTEM (JR405E) 7A2-87
DTC P1875 (Flash Code 25)
Circuit Description
The all shift solenoid valves feed drive voltage from the
TCM and low side circuit is connected to the TCM
through the ground return circuit. The TCM monitors
the ground return circuit through the feedback circuit. If
the TCM detects an improper status on the ground
return 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 on the ground return circuit.
Action Taken When the DTC Sets • The TCM blinks the Check Trans lamp when the diagnostic runs and fails.
• 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.
• The TCM inhibits lock up control.
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.
Schematic Reference: Transmission Controls
Schematics
Connector End View Reference: Transmission
Controls Connector End Views or TCM Connector End
Views
Circuit/ System Testing DTC P1875
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 DTC Information with a scan tool.
Does the DTC fail this ignition? —
Go to Step 3 Go to Diagnostic
Aids
3 1. 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 ground return circuit (pin 11 of E-54 male side) and
battery voltage.
Does the test lamp illuminate? —
Go to Step 4 Go to Step 7
4 1. Inspect for an intermittent and for a poor
connection at the in-line harness connector
(pin 11 of E-54).
2. Repair the connection(s) as necessary.
Did you find and correct the condition? —
Go to Step 9 Go to Step 5
5 1. Test the circuit between the TCM (pin 22 of C-
95) and the in-line harness connector (pin 11
of E-54 female side) for an open circuit or high
resistance.
2. Repair the circuit(s) as necessary.
Did you find and correct the condition? —
Go to Step 9 Go to Step 6
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ISUZU KB P190 2007
Page 4372 of 6020

7A2-88 TRANSMISSION CONTROL SYSTEM (JR405E)
61. 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 22 of C-95).
4. Repair the connection(s) as necessary.
Did you find and correct the condition? —
Go to Step 9 Go to Step 8
7 1. Remove the transmission oil pan. Refer to
repair instructions (On-Vehicle Service).
2. Inspect for an intermittent and for a poor connection at the ground terminal or in-line
harness connector. Clean or tighten grounds
as necessary.
3. Repair the open circuit or high between the ground terminal and the in-line harness
connector (pin 11 of E-54 male side).
Did you complete the repair? —
Go to Step 9 —
8 Important:
Replacement TCM must be
programmed.
Replace the TCM. Refer to TCM Replacement.
Did you complete the replacement? —
Go to Step 9 —
9 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.
Did the DTC fail this ignition? —
Go to Step 3 Go to Step 10
10 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
Page 4373 of 6020

TRANSMISSION CONTROL SYSTEM (JR405E) 7A2-89
Check Trans Lamp Inoperative, Always On or Always Blinking
Circuit Description
The Check Trans Lamp is located on the instrument
panel (IP) cluster. The Check Trans Lamp informs the
driver that a transmission control system fault has
occurred and that system requires service. The ignition
voltage is supplied to the Check Trans Lamp via meter
fuse. The TCM turns ON by grounding the lamp control
circuit. Check Trans Lamp Illumination
• The Check Trans Lamp illuminates for approximately 3 seconds when the ignition switch
is turned ON, with the engine OFF.
• The Check Trans Lamp blinks if the TCM detects a fault.
Schematic Reference: Transmission Controls
Schematics
Connector End View Reference: Transmission
Controls Connector End Views or TCM Connector End
Views
Circuit/ System Testing Check Trans Lamp Inoperative, Always On or Always Blinking
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. Verify whether the instrument panel (IP)
cluster is operational.
2. Turn OFF the ignition for 30 seconds.
3. Turn ON the ignition, with the engine OFF.
Does the check trans lamp turn ON then turn OFF
after 3 seconds passed? —
Go to Intermittent Conditions Go to Step 3
3 Does the check trans lamp blink?
—Check for DTCs and
if none exist Go to
Step 4 Go to Step 6
4 1. Install a scan tool.
2. Turn ON the ignition, with the engine OFF.
3. Observe the Diagnostic Switch parameter with a scan tool.
Does the Diagnostic Switch parameter indicate
ON? —
Go to Step 5 Check for DTCs
5 Repair the short to ground between the TCM (pin
18 of C-94) and the data link connector (DLC) (pin
11 o f B - 5 8 ) .
Did you complete the repair? —
Go to Step 21 —
6 1. Perform the Check Light control with a scan
tool.
2. Command the lamp ON and OFF.
Does the check trans lamp turn ON and OFF with
each command? —
Go to Intermittent Conditions Go to Step 7
7 1. Turn OFF the ignition.
2. Inspect the Meter (10A) fuse in the cabin fuse block.
Is the Meter (10A) fuse open? —
Go to Step 8 Go to Step 9
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ISUZU KB P190 2007
Page 4374 of 6020

7A2-90 TRANSMISSION CONTROL SYSTEM (JR405E)
8Replace the Meter (10A) fuse. If the fuse continues
to open, repair the short to ground on one of the
circuits that is fed by the Meter (10A) fuse or
replace the shorted attached component.
Did you complete the repair? —
Go to Step 21 —
9 1. Turn OFF the ignition.
2. Disconnect the TCM C-94 harness connector.
3. Turn ON the ignition, with the engine OFF.
Is the check trans lamp OFF? —
Go to Step 10 Go to Step 16
10 1. Remove the Meter (10A) fuse that supplies
voltage to the Check Trans Lamp.
2. Turn ON the ignition, with the engine OFF.
3. Measure the voltage from the check trans lamp control circuit in the TCM harness
connector (pin 20 of C-94) to a known good
ground.
Is the voltage less than the specified value? 1 volt
Go to Step 11 Go to Step 17
11 1. Turn OFF the ignition.
2. Reinstall the Meter (10A) fuse.
3. Turn ON the ignition, with the engine OFF.
4. Connect a 3-amp fused jumper wire between the TCM harness connector (pin 20 of C-94)
and a known good ground.
Is the check trans lamp illuminated? —
Go to Step 15 Go to Step 12
12 1. Turn OFF the ignition.
2. Remove the IP cluster.
3. Connect a test lamp between the ignition voltage feed circuit of the IP cluster harness
connector (pin 8 of B-24) and a known good
ground.
4. Turn ON the ignition, with the engine OFF.
Does the test lamp illuminate? —
Go to Step 13 Go to Step 18
13 1. Test the control circuit between the TCM (pin
20 of C-94) and the IP cluster (pin 25 of B-23)
for an open circuit or high resistance.
2. Repair the circuit(s) as necessary.
Did you find and correct the condition? —
Go to Step 21 Go to Step 14
14 1. Inspect for an intermittent and for poor
connections at the harness connector of the
IP cluster (pin 25 of B-23 and pin 8 of B-24).
2. Repair the connection(s) as necessary.
Did you find and correct the condition? —
Go to Step 21 Go to Step 19
15 1. Inspect for an intermittent and for a poor
connection at the harness connector of the
TCM (pin 20 of C-94).
2. Repair the connection(s) as necessary.
Did you find and correct the condition? —
Go to Step 21 Go to Step 20
16 Repair the short to ground between the TCM (pin
20 of C-94) and the IP cluster (pin 25 of B-23).
Did you complete the repair? —
Go to Step 21 —
Step
Action Value(s)Yes No
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ISUZU KB P190 2007
Page 4375 of 6020
TRANSMISSION CONTROL SYSTEM (JR405E) 7A2-91
17Repair the short to battery or ignition voltage
between the TCM (pin 20 of C-94) and the IP
cluster (pin 25 of B-23).
Did you complete the repair? —
Go to Step 21 —
18 Repair the open circuit or high resistance on
ignition the voltage feed circuit between the Meter
(10A) fuse and the IP cluster (pin 8 of B-24).
Did you complete the repair? —
Go to Step 21 —
19 Repair or replace the IP cluster.
Did you complete the repair or replacement? —
Go to Step 21 —
20 Important:
Replacement TCM must be
programmed.
Replace the TCM. Refer to TCM Replacement.
Did you complete the replacement? —
Go to Step 21 —
21 1. Reconnect all previously disconnected fuse or
harness connector(s).
2. Perform the Check Light control with a scan tool.
3. Command the lamp ON and OFF.
Does the check trans lamp turn ON and OFF with
each command? —
System OK Go to Step 7
Step
Action Value(s)Yes No
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ISUZU KB P190 2007
Page 4376 of 6020

7A2-92 TRANSMISSION CONTROL SYSTEM (JR405E)
Symptoms - Transmission Controls
Symptoms - Transmission Controls
Important Preliminary Inspections Before Starting
Perform Diagnostic System Check - Transmission
Controls before using the symptom tables, and verify
that all of the following are true:
• The TCM and check trans lamp is operating correctly.
• The scan tool data is within the normal operating range. Refer to Scan Tool Data List in this section.
• Verify the customer concern and locate the correct symptom in the table of contents. Inspect the items
indicated under that symptom.
Visual and Physical Inspection
Several of the symptom procedures ask for careful
visual and physical inspection. This step is extremely
important. The visual and physical inspection can lead
to correcting a problem without further inspections, and
can save valuable time. Ensure that:
• The TCM grounds are clean, tight, and in their proper location.
• The transmission harness wiring and terminals are properly connected and are not pinched or cut.
Intermittent
Important: Inspect for improper installation of electrical
components if an intermittent condition exists. Inspect
for aftermarket add-on electrical equipment devices,
lights, and cellular phones. Verify that no aftermarket
equipment is connected to the serial data circuit.
Important: The problem may or may not turn ON the
check trans lamp or store a DTC. Faulty electrical
connections or wiring cause most intermittent
problems.
Perform a careful visual and physical inspection of the
suspect connectors for the following conditions:
• Improperly mated connector halves
• Terminals that are not seated
• Terminals that are damaged or improperly formed
Reform or replace connector terminals in the problem
circuit in order to ensure proper contact tension.
Remove the terminal from the connector body in order
to inspect for poor terminal wire connection.
Road test the vehicle with the DMM connected to the
suspected circuit. An abnormal reading that occurs
when the malfunction occurs is a good indication that
there is a malfunction in the circuit being monitored.
Use the scan tool in order to help detect intermittent
conditions. Useful features of the Tech 2 includes the
following: • Trigger the Snapshot feature in order to capture
and store transmission parameters when the
malfunction occurs. Review this stored information
in order to see the specific running conditions that
caused the malfunction.
• Use the Plot Function on the scan tool in order to plot selected data parameters. Review this stored
information to aid in locating an intermittent
problem. Refer to the scan tool Users Guide for
more information.
Important: If the intermittent condition exists as a start
and then stall, test for DTCs relating to the vehicle theft
deterrent system. Test for improper installation of
electrical options such as lights, cellular phones, etc.
Any of the following may cause an intermittent check
trans lamp with no stored DTC:
• The TCM grounds are loose or dirty. Refer to Transmission Controls Schematics.
• The check trans lamp circuit intermittently shorted to ground
• Electrical system interference caused by a malfunctioning relay, TCM driven solenoid, or
switch. The electrical component can cause a
sharp electrical surge. Normally, the problem will
occur when the malfunctioning component is
operating.
• There are any open diodes.
Important: The following symptom tables contain
groups of possible causes for each symptom. The
order of these procedures is not important. If the scan
tool readings do not indicate the problems, then
proceed in a logical order, easiest to check or most
likely to cause first. In order to determine if a specific
vehicle is using a particular system or component, refer
to Transmission Controls Schematics for an
application.
Use the following tables when diagnosing a symptom
complaint:
• Intermittent Conditions
• Vehicle Does Not Run
• Trouble at Starting
• Faulty Gearshift
• Faulty Shift Pattern
• No or Error Gearshift
• Faulty Operation During Running
• Faulty Operation in Stopping
• Faulty Lock Up
• No Lock Up
• Transmission Fluid Leak
•Others
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ISUZU KB P190 2007