Isuzu Trooper (1998-2002 year). Manual - part 794

TRANSMISSION CONTROL SYSTEM (4L30–E)

7A1–85

DTC P1850 Brake Band Apply Solenoid Malfunction  (Cont’d)

Step

No

Yes

Action

21

The brake band apply solenoid is faulty, or the internal wiring
harness from the brake band apply solenoid is open.

Was a problem found and corrected?

Go to Step 27

—

22

The wiring harness between the PCM connector terminal S–10
and transmission 16–way connector terminal H69–9 (LHD) or
H69–12 (RHD) is shorted to ground.

Was a problem found and corrected?

Go to Step 27

—

23

The wiring harness between the transmission 16–way connector
terminal H69–9 (LHD) or H69–12 (RHD) and the transmission
main case connector terminal M7–7(B) is shorted to ground.

Was a problem found and corrected?

Go to Step 27

—

24

The wiring harness between the PCM connector terminal S–10
and the 16–way connector terminal H69–9 (LHD) or H69–12
(RHD) is open.

Was a problem found and corrected?

Go to Step 27

—

25

The wiring harness between the transmission 16–way connector
terminal H69–9 (LHD) or H69–12 (RHD) and the transmission
main case connector terminal M7–7(B) is open.

Was a problem found and corrected?

Go to Step 27

—

26

Check every connection at the PCM.
If OK, replace the PCM. Refer to Powertrain Control Module
(PCM) in Automatic Transmission (4L30–E) section.

Is the replacement complete?

Go to Step 27

—

27

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

then “Clear Info” function and ensure the following conditions
are met:

D

The brake band apply solenoid is commanded “on” and the
volts drop to zero.

D

The brake band apply solenoid is commanded “off” and the
volts increase to B+.

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

7A1–86 TRANSMISSION CONTROL SYSTEM (4L30–E)

DTC P1860 TCC PWM Solenoid Electrical

D07R200055

Circuit Description

The PCM allows current to flow through the solenoid coil
according to the duty cycle (percentage of “on” and “off”
time).  This current flow through the solenoid coil creates
a magnetic field that magnetizes the solid core.  The
magnetized core attracts the check ball to seat against
spring pressure.  This blocks the exhaust for the TCC
signal fluid and allows solenoid feed drive fluid to feed to
TCC signal circuit.  The TCC signal fluid pressure acts on
the TCC regulator valve to regulate line pressure and to
apply fluid pressure to the torque converter clutch shift
control valve.  When the TCC control valve is in the apply
position, regulated apply fluid pressure is directed
through the TCC valve to apply the torque converter
clutch.  The TCC PWM solenoid is used in conjunction
with the TCC reglator valve to regulate fluid to the torque
converter.  The TCC PWM solenoid is attached to the
valve body within the transmission.
This DTC detects a continuous open or short to ground or
ignition in the TCC circuit or the TCC PWM solenoid.  This
is a type “B” DTC.

Conditions For Setting The DTC

D

Battery voltage is between 10 and 16 volts.

D

No shift solenoid A DTCs P0751 or P0752 or P0753.

D

No shift solenoid B DTCs P0756 or P0757 or P0758.

D

Ignition is “on”, Engine “run”.

D

The PCM commands the solenoid “on” and the
voltage remains low (zero volts).

D

The PCM commands the solenoid “off” and the
voltage remains high (B+).

D

All conditions met for 0.875 

∼

 1.25 seconds.

Action Taken When The DTC Sets

D

Inhibit TCC engagement.

D

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

Conditions For Clearing The MIL/DTC

D

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

D

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

D

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

D

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

D

Inspect the wiring for poor electrical connections at
the PCM and at the transmission 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.

D

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:
3. This test checks for voltage to the solenoid.
4. This test checks the ability of the PCM and wiring to

control the ignition circuit.

9. This test checks the resistance of the TCC solenoid

and the internal wiring harness.

TRANSMISSION CONTROL SYSTEM (4L30–E)

7A1–87

DTC P1860 TCC PWM Solenoid Electrical 

Step

Action

Yes

No

1

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

2

1. Install the scan tool.
2. With the engine “on”, 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”.

Go to Step 3

Go to Step 4

3

Using the J39200 DVOM, back probe between PCM connector
terminals S–51 and S–33.

Is the voltage 0 ?

Go to Step 5

Go to Step 6

4

1. Apply brake pedal and select transmission range “D”.
2. Do a test drive, and increase the vehicle speed to TCC “on” at

4th.

Does the scan tool display DTC P1860 at TCC “ON”?

Go to Step 10

Go to Diagnostic

Aids

5

1. Turn the ignition “off”.
2. Disconnect the S (RED) PCM connector.
3. Using the J39200 DVOM, measure the resistance between

PCM connector terminals S–51 and S–33.

Is the resistance 10

±

0.5 ohms at 20

°

C (68

°

F) ?

Go to Step 7

Go to Step 8

6

The wiring harness between PCM connector terminal S–51 and
transmission adapter case connector terminal M6–1(A) is shorted
to voltage.

Was a problem found and corrected?

Go to Step 19

Go to Step 20

7

Intermittent condition.
Check the wiring harness and terminals between PCM connector
S and transmission adapter case connector M–6.

Was a problem found and corrected?

Go to Step 19

Go to Step 20

8

1. Disconnect the transmission 4–way connector H–54.
2. Using the J39200 DVOM, measure the resistance between

terminal H54–2 and ground.

Is the resistance 10

±

0.5 ohms at 20

°

C (68

°

F) ?

Go to Step 16

Go to Step 9

9

1. Disconnect the transmission adapter case connector M–6.
2. Using the J39200 DVOM, measure the resistance between

terminal M6–1(A) and ground.

Is the resistance 10

±

0.5 ohms at 20

°

C (68

°

F) ?

Go to Step 17

Go to Step 18

10

1. Turn the ignition “off”.
2. Disconnect the S (RED) PCM connector.
3. Using the J39200 DVOM, measure the resistance between

terminals S–51 and S–33.

Is the resistance 10

±

0.5 ohms at 20

°

C (68

°

F) ?

Go to Step 19

Go to Step 11

11

1. Disconnect the transmission 4–way connector H–54.
2. Using the J39200 DVOM, measure the resistance between

terminal H54–2 and ground.

Is the resistance 10

±

0.5 ohms at 20

°

C (68

°

F) ?

Go to Step 13

Go to Step 12

7A1–88 TRANSMISSION CONTROL SYSTEM (4L30–E)

DTC P1860 TCC PWM Solenoid Electrical  (Cont’d)

Step

No

Yes

Action

12

1. Disconnect the transmission adapter case connector M–6.
2. Using the J39200 DVOM, measure the resistance between

terminal M6–1(A) and ground.

Is the resistance 10

±

0.5 ohms at 20

°

C (68

°

F) ?

Go to Step 14

Go to Step 15

13

The wiring harness between PCM connector terminal S–51 and
transmission 4–way connector terminal H54–2 is shorted to
ground.

Was a problem found and corrected?

Go to Step 21

—

14

The wiring harness between transmission 4–way connector H–54
and adapter case connector M–6 is shorted to ground.

Was a problem found and corrected?

Go to Step 21

—

15

The TCC solenoid is faulty, or the internal wiring harness from the
TCC solenoid is shorted to ground.

Was a problem found and corrected?

Go to Step 21

—

16

The wiring harness between PCM connector terminal S–51 and
transmission 4–way connector terminal H54–2 is open.

Was a problem found and corrected?

Go to Step 21

—

17

The wiring harness between transmission 4–way connector
terminal H54–2 and adapter case terminal M6–1(A) is open.

Was a problem found and corrected?

Go to Step 21

—

18

The TCC solenoid is faulty, or the internal wiring harness from the
TCC solenoid is open.

Was a problem found and corrected?

Go to Step 21

—

19

Check every connection at the PCM.
If OK, replace the PCM. Refer to Powertrain Control Module
(PCM) in Automatic Transmission (4L30–E) section.

Is the replacement complete?

Go to Step 21

—

20

Check the PCM connector terminal S–51, transmission 4–way
connector terminal H54–2 and transmission adapter case
connector terminal M6–1(A).

Was a problem found and corrected?

Go to Step 21

—

21

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

then “Clear Info” function and ensure the following conditions
are met:

D

The TCC solenoid is commanded “on” and the volts increase
to B+.

D

The TCC solenoid is commanded “off” and the volts drop to
zero.

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