Isuzu Trooper (1998-2002 year). Manual - part 788

TRANSMISSION CONTROL SYSTEM (4L30–E)

7A1–61

Diagnostic Aids

If the TCC is mechanically stuck “on” with the parking
brake applied and any gear range selected, the TCC
fluid will mechanically apply the TCC, possibly
causing an engine stall.

Test Description

The number below refers to the step number on the
diagnostic chart:
3. This test checks the mechanical state of the TCC.

(When the PCM commands the TCC solenoid “off”,
the slip speed should increase).

DTC P0742 Torque Converter Clutch (TCC) System Stuck On

Step

Action

Yes

Were you sent here from the “Powertrain On–Board Diagnostic
(OBD) System Check”?

Go to Step 2

Go to OBD

System Check

Refer to

Driveability and

Emissions in

Engine section

1. Install the scan tool.
2. With the engine “off”, turn the ignition switch “on”.

NOTE: Before clearing DTC(s), use the scan tool to record “Freeze
Frame” and “Failure Records” for reference, as data will be lost
when the “Clear Info” function is used.

3. Record the DTC “Freeze Frame” and “Failure Records”.
4. Using the scan tool, verify the “TP Sensor” operation.

Are the “TP Sensor” values within 0.6 – 5.0 volts?

Go to Step 3

Go to Diagnostic

Aids

Drive the vehicle in the D4 drive range in fourth gear under steady
acceleration, with a TP angle greater than 20%.

Does the scan tool display “TCC Slip Speed” between –30 and
+30 rpm, while the displayed TCC solenoid state is “off”?

Go to Step 4

Go to Diagnostic

Aids

The TCC is mechanically stuck “on”. Check the following items:

Clogged exhaust orifice in the TCC solenoid.

Converter clutch apply valve stuck in the apply position.

Misaligned or damaged valve body gasket.

Restricted release passage.

Was a problem found and corrected?

Go to Step 5

—

1. After the repair is complete, use the scan tool to select “DTC”,

then “Clear Info” function and ensure the following conditions
are met:
TCC slip speed must be between 200 and 2,500 rpm for 4
seconds.

2. Review the scan tool “DTC Info”.

Has the last test failed or is the current DTC displayed?

Begin diagnosis

again

Go to Step 1

Repair verified
Exit DTC table

7A1–62 TRANSMISSION CONTROL SYSTEM (4L30–E)

DTC P0748 Pressure Control Solenoid (PCS) (Force Motor) Circuit Electrical

D07R200052

Circuit Description

The PCS is a PCM–controlled device used to regulate
transmission line pressure. The PCM compares TPS
voltage, engine rpm, and other inputs to determine the
line pressure appropriate for a given load. The PCM will
regulate the pressure by applying a varying amperage to
the PCS. The applied amperage can vary from 70 to 1060
milliampere (mA), and is monitored by the PCM.
This DTC detects a continuous open or short to ground in
the PCS circuit or the PCS. This is a type “C” DTC.

Conditions For Setting The DTC

Battery voltage is between 10 and 16 volts.

The PCM detects that the different between
commanded and actual current is 200 milliampere
(mA) for over 1 second.

Engine speed is greater than 300 rpm.

Action Taken When the DTC Sets

The PCM will not illuminate the Malfunction Indicator
Lamp (MIL).

Maximum line pressure.

The PCM will illuminate the CHECK TRANS Lamp.

Turn force motor OFF (Durability).

Conditions For Clearing The DTC/CHECK
TRANS Lamp

The PCM will turn “off” the CHECK TRANS Lamp
after three consecutive ignition cycles without a
failure reported.

The DTC can be cleared from PCM history by using a
scan tool.

The DTC will be cleared from memory when the
vehicle has achieved 40 warmup cycles without a
failure reported.

The PCM will cancel the DTC default actions when
the fault no longer exists and the ignition is cycled “off”
long enough to power down the PCM.

Diagnostic Aids

Inspect the wiring for poor electrical connection at the
PCM and at the transmission 4–way connector. Look
for possible bent, backed out, deformed or damaged
terminals. Check for weak terminal tension as well.
Also check for a chafed wire that could short to bare
metal or other wiring. Inspect for a broken wire inside
the insulation.

When diagnosing for a possible intermittent short or
open condition, move the wiring harness while
observing test equipment for a change.

Test Description

The numbers below refer to the step numbers on the
diagnostic chart:
2. This test checks the ability of the PCM to command

the PCS.

3. This test checks the PCS and internal wiring harness

for incorrect resistance.

TRANSMISSION CONTROL SYSTEM (4L30–E)

7A1–63

DTC P0748 Pressure Control Solenoid (PCS) (Force Motor) Circuit Electrical

Step

Action

Yes

Were you sent here from the “Powertrain On–Board Diagnostic
(OBD) System Check”?

Go to Step 2

Go to OBD

System Check

Refer to

Driveability and

Emission in

Engine section

1. Install the scan tool.
2. With the engine “off”, turn the ignition switch “on”.

NOTE: Before clearing DTC(s), use the scan tool to record “Failure
Records” for reference, as data will be lost when the “Clear Info”
function is used.

3. Record the DTC “Failure Records”.
4. While the engine is operating, put the transmission in Park.
5. Using the scan tool, apply 70 through 1060 milliampere (mA)

while observing “PC Ref. Current” and “PC Act. Current”.

Is the “PC Act. Current” reading always within 160 mA?

Go to Diagnostic

Aids

Go to Step 3

1. Turn the ignition “off”.
2. Disconnect the transmission 4–way connector M–6.
3. Using the J39200 DVOM, measure the resistance between

terminals M6–2(B) and M6–4(C).

Is the resistance within 3–7 ohms?

Go to Step 7

Go to Step 4

1. Remove the transmission oil pan. Refer to Solenoid (Adapter

Case Valve Body) in Automatic Transmission (4L30–E)
section.

2. Disconnect the internal wiring harness at the PCS.
3. Measure the resistance of the PCS.

Is the resistance within 3–7 ohms?

Go to Step 6

Go to Step 5

Replace the PCS.

Is the replacement complete?

Go to Step 10

—

Repair the internal wiring harness for an open.

Is the repair complete?

Go to Step 10

—

Inspect/repair circuits F–47, M6–2(B), F–43, and M6–4(C).

Was a problem found?

Go to Step 10

Go to Step 8

Inspect/repair circuits F–47, M6–2(B), F–43, and M6–4(C) for a
short to ground or poor connections.

Was a problem found?

Go to Step 10

Go to Step 9

Replace the PCM. Refer to Powertrain Control Module (PCM) in
Automatic Transmission (4L30–E) section.

Is the replacement complete?

Go to Step 10

—

1. After the repair is complete, use the scan tool to select “DTC”,

then “Clear Info” function and ensure the following conditions
are met:
The PCS duty cycle is not at its electrical high or low limit.

2. Review the scan tool “DTC Info”.

Has the last test failed or is the current DTC displayed?

Begin diagnosis

again

Go to Step 1

Repair verified
Exit DTC table

7A1–64 TRANSMISSION CONTROL SYSTEM (4L30–E)

DTC P0751 Shift Solenoid A Performance (Stuck OFF)

D07RT011

Circuit Description

The shift solenoid A is used to control fluid flow acting on
the 1–2 and 3–4 shift valves. The solenoid is a normally
close exhaust valve that is used with the shift solenoid B
to allow four different shifting combinations.
The DTC detects when there is only a 1–1–4–4 shift
pattern depending on the state of the mechanical failure
instead of a 1–2–3–4 shift pattern. This is a type “B” DTC.

Conditions For Setting The DTC

No ETC DTCs.

No OSS DTCs P0722 or P0723.

No TCC solenoid DTC P0742, P1860, P1870.

No shift solenoid A DTC P0753.

No shift solenoid B DTC P0758.

Gear range is D4.

Output speed is greater than 375 rpm.

Transmission temperature is between 20

and 130

(68

and 266

F).

No range code P0705, P0706.

No torque code (to be confirmed).

Engine run for more 0 seconds and not influed cut-off
(to be confirmed).

All the above conditions have been met and the
combination of conditions 1, 2 occur two consecutive
times.

Condition 1:

2nd gear is commanded for

≥

1 sec

≤

Engine Torque

≤

400 N·m

Throttle positon

≥

10%

800

≤

TCC slip

≤

4000 rpm

Speed ratio

≥

0.6

2.75

≤

Modeled Ratio

≤

3.2 for 1 seconds.

Condition 2:

3rd Gear is commanded for

≥

1 sec.

≤

Engine Torque

≤

400 N·m

Trottle position

≥

10%

–8000

≤

TCC slip

≤

8000 rpm

Speed ratio

≥

0.45

0.62

≤

Modeled Ratio

≤

0.92 for 3 seconds

Action Taken When the DTC Sets

Maximum line pressure.

For lamp illuminate refer to DTC type definition (type
B).

Turn force motor OFF.

Conditions For Clearing The The MIL/DTC

The PCM will turn off the MIL and CHECK TRANS
Lamp after three consecutive ignition cycles without a
failure reported.

The DTC can be cleared from the PCM history by
using a scan tool.

The DTC will be cleared from history when the vehicle
has achieved 40 warmup cycles without a failure
reported.

The PCM will cancel the DTC default actions when
the fault no longer exists and the ignition is cycled “off”
long enough to power down the PCM.

Diagnostic Aids

Verify that the transmission meets the specifications
in the 4L30–E shift speed chart.

Other internal transmission failures may allow more
than one shift to occur.

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