Isuzu KB P190. Manual - part 1084

7A2-52 TRANSMISSION CONTROL SYSTEM (JR405E)

DTC P0731, P0732, P0733 or P0734 (Flash Code 41, 42, 43 or 44)

Circuit Description

The TCM calculates the gear ratio based on the input
shaft speed signal from the input shaft speed (ISS)
sensor and the output speed signal from the output
shaft speed (OSS) sensor. The TCM compares the
known transmission gear ratio to the calculated ratio for
the selected gear ranges. If the TCM detects an
unknown transmission gear ratio two consecutive
driving cycles, this DTC will set.

Condition for Running the DTC

• Other than DTCs P0731, P0732, P0733 and

P0734 are not set.

• The ignition switch is ON.

• The transmission fluid temperature is more than

°C (140°F).

• The input shaft speed is more than 1000 RPM.

• The vehicle speed is more than 10 km/h (6 MPH).

• The selector lever is forward range for longer than

2 seconds.

• The TCM is not under gearshift control.

Condition for Setting the DTC

• The TCM detects that the output shaft speed is

more than 500 RPM over the calculated speed
(based on the input shaft speed and the gear ratio)
for 7 seconds after each gearshift has completed.

Action Taken When the DTC Sets

• The TCM blinks the Check Trans lamp on the

second consecutive driving cycle 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.

• Electromagnetic interference in the ISS sensor or

OSS sensor circuits may set this DTC.

• An intermittent ISS sensor or OSS sensor signal

pulse may set this DTC.

• Ensure the ISS sensor and OSS sensor is tight.

• Use the Clutch, Brake, Solenoid and Pressure

Switch Logic table to verify each component works
properly within the selected gear range.

• A transmission mechanical problem will cause this

DTC to set.

• Sticking or contamination of shift valves may cause

intermittent incorrect gear ratios.

• If multiple incorrect gear ratio codes are set,

problem in fluid pressure, low ATF level, plugged
filter or oil pump problem may exist.

Notice:

• Each DTC agrees with the following gear

positions.
- P0731: 1st gear
- P0732: 2nd gear
- P0733: 3rd gear
- P0734: 4th gear

Schematic Reference: Transmission Controls
Schematics
Connector End View Reference: Transmission
Controls Connector End Views or TCM Connector End
Views

Circuit/ System Testing DTC P0731, P0732, P0733 or P0734

Step

Action

Value(s)

Yes

Did you perform the Diagnostic System Check -
Transmission Controls?

—

Go to Step 2

Go to Diagnostic

System Check -

Transmission

Controls

Perform the ATF level check. Refer to repair
instructions (On-Vehicle Service).

Did you perform the ATF level check?

—

Go to Step 3

Go to Transmission

Fluid Checking

Procedure

Install a scan tool.

Turn OFF the ignition for 30 seconds.

Drive the vehicle while observing the DTC
Information with a scan tool.

Is there any DTCs set other than P0731, P0732,
P0733 or P0734?

—

Refer to Applicable

DTC

Go to Step 4

TRANSMISSION CONTROL SYSTEM (JR405E) 7A2-53

Inspect all of the circuits going to the input
shaft speed (ISS) sensor and the output shaft
speed (OSS) sensor for the following
conditions:

• Routed too closely to fuel injection wiring

or components

• Routed too closely to after-market add-

on electrical equipment

• Routed too closely to solenoids and

relays

If you find incorrect routing, correct the
harness routing.

Did you find and correct the condition?

—

Go to Step 13

Go to Step 5

Disconnect the ISS sensor and the OSS
sensor harness connector.

Inspect for an intermittent, for poor
connections and corrosion at the harness
connector of the ISS sensor (pins 1, 2 and 3 of
E-31) and the OSS sensor (pins 1,2 and 3 of
E-30).

Disconnect the TCM harness connector.

Inspect for an intermittent, for poor
connections and corrosion at the harness
connector of the TCM (pins 3 and 13 of C-95).

Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 13

Go to Step 6

Inspect the ISS sensor and the OSS sensor
for the following conditions:

• Physical damage of sensor

• Loose or improper installation of sensor

• Excessive air gap

• Foreign material passing between ISS

sensor and reverse & high clutch drum

• Foreign material passing between OSS

sensor and parking gear

• Physical damage of reverse & high clutch

drum or parking gear

Repair or replace as necessary.

Did you find and correct the condition?

—

Go to Step 13

Go to Step 7

Place the selector lever in D range.

Observe the Low & Reverse Brake Pressure
Switch, 2-4 Brake Pressure Switch and High
Clutch Pressure Switch parameter with a scan
tool. Refer to Clutch, Brake, Solenoid and
Pressure Switch Logic table.

Does the each transmission fluid pressure (TFP)
switch display match each selected gear range?

—

Go to Step 8

Refer to DTC

P1853, P1858 or

P1863

Perform the line pressure test. Refer to Line
Pressure Test.

Is the line pressure within specifications for each
selected gear range?

—

Go to Step 9

Refer to appropriate

instructions in the

Line Pressure Test

Step

Action

Value(s)

Yes

7A2-54 TRANSMISSION CONTROL SYSTEM (JR405E)

Remove the transmission oil pan. Refer to
repair instruction (On-Vehicle Service).

Inspect the oil pan and the fluid for
contamination.

Was excessive contamination found?

—

Replace the

transmission fluid

and filter and Go to

Step 10

Go to Step 11

Drive the vehicle while observing the DTC
Information with a scan tool.

Does the DTC fail this ignition?

—

Go to Step 11

Go to Step 13

Remove the all shift solenoid valve and all
TFP switch from the valve body assembly and
perform function check. Refer to repair
instructions (On-Vehicle Service).

Repair or replace as necessary.

Did you find and correct the condition?

—

Go to Step 13

Go to Step 12

Repair or replace the valve body assembly/
clutches or brakes (On-Vehicle Service or Unit
Repair).

Did you complete the repair or replacement?

—

Go to Step 13

—

Reconnect all previously disconnected
components or harness connector(s).

Clear the DTCs with a scan tool.

Turn OFF the ignition for 30 seconds.

Start the engine.

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

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

TRANSMISSION CONTROL SYSTEM (JR405E) 7A2-55

DTC P0748 (Flash Code 35)

Circuit Description

The pressure control (PC) solenoid valve is installed to
the lower part of the valve body assembly. It controls
the transmission fluid supply to the pressure regulator
spool valve in the valve body. The TCM controls the
solenoid valve by ON/ OFF signal based on the vehicle
running conditions. The TCM turns ON the solenoid
valve when a lower line pressure is required and turns
OFF when a higher line pressure is required. With the
operation of this solenoid valve, the operation and shift
of the hydraulic circuit in the transmission can be
performed smoothly. The PC solenoid valve is
controlled according to the range position, speed
sensor signals, transmission fluid temperature signal
and the accelerator pedal position signal. The TCM
monitors the PC 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 PC solenoid valve control circuit.

Action Taken When the DTC Sets

• The TCM blinks the Check Trans lamp when the

diagnostic runs and fails.

• 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.

Schematic Reference: Transmission Controls
Schematics
Connector End View Reference: Transmission
Controls Connector End Views or TCM Connector End
Views

Circuit/ System Testing DTC P0748

Step

Action

Value(s)

Yes

Did you perform the Diagnostic System Check -
Transmission Controls?

—

Go to Step 2

Go to Diagnostic

System Check -

Transmission

Controls

Install a scan tool.

Perform the Pressure Control (PC) Solenoid
control with a scan tool.

Command the solenoid valve ON and OFF.

Does the PC solenoid valve click with each
command?

—

Go to Diagnostic

Aids

Go to Step 3

Turn OFF the ignition.

Disconnect the in-line harness connector (E-
54) near the transmission range switch.

Connect a test lamp between the control
circuit (pin 6 of E-54 female side) and a known
good ground.

Turn ON the ignition, with the engine OFF.

Perform the PC Solenoid control with a scan
tool.

Command the solenoid valve ON and OFF.

Does the test lamp turn ON and OFF with each
command?

—

Go to Step 8

Go to Step 4

Does the test lamp remain illuminated with each
command?

—

Go to Step 5

Go to Step 6

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