Isuzu KB P190. Manual - part 965

Automatic Transmission – 4L60E – Electrical Diagnosis

Page 7C2–74

•

Tech 2 can clear the DTC.

•

The TCM clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without a non-emission
related diagnostic fault occurring.

•

The TCM cancels the DTC default actions when the ignition is off long enough to power down the TCM.

Test Description

The following numbers refer to the step numbers in the diagnostic table:

Checks the ability of the TCM to control the solenoid.

Checks for supply voltage to the 3-2 SS valve.

Checks the ability of the TCM and wiring to control the ground circuit.

Checks the resistance of the control valve body wiring harness and the 3-2 SS valve.

Checks if the 3-2 SS or control valve body wiring harness is shorted to the transmission housing.

Checks if the control valve body wiring harness is shorted to ground.

Checks if any of the other solenoids in the transmission are shorted to ground.

DTC P0787 Diagnostic Table

Step Action

Yes

Has the Diagnostic System Check been performed?

Go to Step 2

Refer to

4.7 Diagnostic

System Check

Connect Tech 2 to the DLC.

Turn on the ignition, with the engine off.

N O T E

Before clearing the DTC, use the Tech

2 Freeze

Frame/Failure Record to record the transmission
parameters at the time the DTC set. Using Tech 2 to clear
the DTC(s) erases the Freeze Frame/Failure Record
records from the TCM.

On Tech 2 select:
Transmission / Automatic Transmission / Diagnostic
Trouble Codes / Freeze Frame.

Select the relevant DTC and note the parameters at the time of
the DTC setting.

On Tech 2 select:
Diagnostic Trouble Codes / Clear Engine & Transmission
DTCs.

Follow the instructions on Tech 2 and clear the DTCs.

Are any of the following DTCs also set?

•

P0961

•

P0973

•

P0976

•

P2764

•

P2769.

Go to Step 3

Go to Step 4

Inspect fuse C-8 and check if it is blown, refer to 8A Electrical-Body
and Chassis.

Is the fuse blown?

Replace the fuse

Go to Step 12

Go to Step 5

Automatic Transmission – 4L60E – Electrical Diagnosis

Page 7C2–75

Step Action

Yes

On Tech 2 select:
Automatic Transmission / Miscellaneous Tests / 3-2
Downshift Solenoid.

With Tech 2 command the 3-2 shift solenoid ON and OFF.

Does Tech 2 display the 3-2 Downshift Solenoid as Active and
Inactive respectively?

Check for an

intermittent fault in

the circuit, refer to

8A Electrical-Body

and Chassis

Go to Step 5

Turn off the ignition.

Disconnect connector E-95 from the transmission.

N O T E

Additional DTCs may set

Install Tool No. J 44152 Jumper Harness (20 pins) on to the
harness connector E-95.

Turn on the ignition, with the engine off.

Using a test lamp, probe between connector E-95 pin 10 and a
known ground.

Does the test lamp illuminate?

Go to Step 6

Test between

E-95 pin 10 and

C-107 pin 9 for an

open circuit

Repalce affected

circuit

Go to Step 18

Using a test lamp, probe connector E-95 pin 10 with the ground
lead to connector E-95 pin 11.

On Tech 2 select:
Automatic Transmission / Miscellaneous Tests / 3-2
Downshift Solenoid.

With Tech 2 command the 3-2 shift solenoid ON and OFF three
times.

Does the test lamp turn on and off with each command?

Go to Step 8

Go to Step 7

Is the test lamp always illuminates?

Go to Step 15

Go to Step 16

Remove Tool No. J44152 from the harness connector E-95 and
install on to the transmission connector E-95.

Using a multimeter set to measure resistance, probe across
transmission connector E-95 pins 10 and 11.

Does the multimeter display 20 – 32

Ω?

Go to Step 9

Go to Step 10

Using a multimeter set to measure resistance, probe between:

•

Transmission connector E-95 pin 10 and a known ground.

•

Transmission connector E-95 pin 11 and a known ground.

Does the multimeter display greater than 250 k

Ω in both instances?

Check for an

intermittent fault in

the circuit, refer to

8A Electrical-Body

and Chassis

Go to Step 11

10 1

Remove Tool No. J44152 from the transmission.

Gain access to the 3-2 SS and the control valve body wiring
harness, refer to 7C4 Automatic Transmission – 4L60E – On-
vehicle Servicing.

Disconnect the internal connector from the 3-2 SS.

Using a multimeter set to measure resistance, probe across the
3-2 SS pins.

Does the multimeter display 20 – 32

Ω?

Replace the control

valve body wiring

harness, refer to

7C4 Automatic

Transmission –

4L60E – On-vehicle

Servicing.

Go to Step 18

Replace the 3-2 SS,

refer to

7C4 Automatic

Transmission –

4L60E – On-vehicle

Servicing.

Go to Step 18

Automatic Transmission – 4L60E – Electrical Diagnosis

Page 7C2–76

Step Action

Yes

11 1

Remove Tool No. J44152 from the transmission.

Gain access to the 3-2 SS and the control valve body wiring
harness, refer to 7C4 Automatic Transmission – 4L60E – On-
vehicle Servicing.

Disconnect the internal connector from the 3-2 SS.

Using a multimeter set to measure resistance, probe between
each of the 3-2 SS pins and the transmission case.

Does the multimeter display 250 k

Ω in both instances?

Replace the control

valve body wiring

harness, refer to

7C4 Automatic

Transmission –

4L60E – On-vehicle

Servicing.

Go to Step 18

Replace the 3-2

shift solenoid, refer

to 7C4 Automatic

Transmission –

4L60E – On-vehicle

Servicing.

Go to Step 18

12 Using a multimeter, test between E-95 pin 10 and C-107 pin 9 for a

short to ground.

Did you find and correct the condition?

Go to Step 18

Go to Step 13

13 1

Gain access to the control valve body wiring harness, refer to
7C4 Automatic Transmission – 4L60E – On-vehicle Servicing.

Test for a short to ground in the control valve body wiring
harness.

Did you find a short to ground condition?

Replace the control

valve body wiring

harness, refer to

7C4 Automatic

Transmission –

4L60E – On-vehicle

Servicing.

Go to Step 18

Go to Step 14

14 1

Test each solenoid in the transmission for a short to ground,
refer to 8A Electrical-Body and Chassis.

Replace the faulty solenoid as necessary.

Did you complete the replacement?

Go to Step 18

—

15 Using a multimeter, test between E-95 pin 11 and C-96 pin 14 for a

short to ground.

Did you find and correct the condition?

Go to Step 18

Go to Step 17

16 Using a multimeter, test between E-95 pin 11 and C-96 pin 14 for an

open circuit.

Did you find and correct the condition?

Go to Step 18

Go to Step 17

17 Replace the TCM, refer to 7C4 Automatic Transmission – 4L60E –

On-vehicle Servicing.

Did you complete the replacement?

Go to Step 18

—

18 Perform the following procedure to verify the repair:

On Tech 2 select:
Diagnostic Trouble Codes / Clear Engine & Transmission
DTCs.

Follow the instructions on Tech 2 and clear any DTCs.

On Tech 2 select:
Automatic Transmission / Data Display / Transmission Data.

Drive the vehicle in D3 or D4 and perform a 3-2 downshift.
Ensure the 3-2 Downshift Solenoid parameter displays On
when the shift occurs.

On Tech 2 select:
Diagnostic Trouble Codes / Read DTC Information.

Has DTC P0787 set?

Go to Step 2

Go to Step 19

19 On Tech 2 select:

Diagnostic Trouble Codes / Read DTC Information.

Does Tech 2 display any DTCs you have not diagnosed?

Refer to

4.8 Diagnostic

Trouble Code List

System OK

Automatic Transmission – 4L60E – Electrical Diagnosis

Page 7C2–77

Step Action

Yes

When all diagnosis and repairs are completed, check the system for correct operation.

4.25 DTC P0788 – 3-2 Shift Solenoid Control

Circuit High Voltage

DTC Description

This diagnostic procedure supports DTC P0788 3-2 Shift Solenoid (SS) Control Circuit High Voltage.

Circuit Description

The 3-2 shift solenoid (SS) valve is a normally-closed, 3-port, on/off device that controls the 3-2 downshift. The solenoid
attaches to the control valve body within the transmission. The solenoid receives ignition voltage through the ignition 1
circuit. The transmission control module (TCM) controls the solenoid by providing a ground path on the 3-2 shift solenoid
valve control circuit. During a 3-2 downshift, the 2-4 band applies as the 3-4 clutch releases. The TCM varies the timing
between the 3-4 clutch release and the 2-4 band apply depending on the vehicle speed and the throttle position.

When the TCM detects a continuous short to voltage in the 3-2 shift solenoid valve control circuit, then DTC P0788 sets.
DTC P0788 is a type A DTC.

Refer to 2

Wiring Diagrams and Connector Chart to aid in diagnosis.

Conditions for Running the DTC

•

The system voltage is 10 – 18 V.

•

The engine speed is 450 r.p.m. for 5 seconds.

•

The engine is not in fuel cut off.

Conditions for Setting the DTC

DTC P0788 sets if the TCM commands the solenoid on and the voltage feedback remains high, battery voltage.

Action Taken When the DTC Sets

•

The TCM requests the ECM to illuminate the MIL during the second consecutive trip in which the Conditions for
Setting the DTC are met.

•

The TCM commands maximum line pressure.

•

The TCM freezes transmission adaptive functions.

•

The TCM commands 3rd gear.

•

The TCM inhibits TCC engagement.

•

At the time of the first failure, the TCM records the operating conditions when the conditions for setting the DTC are
met. The TCM stores this information as a Failure Record.

•

At the time of the second failure, the ECM records the operating conditions when the conditions for setting the DTC
are met. The ECM stores this information as a Freeze Frame.

•

The TCM stores DTC P0788 in TCM history during the second consecutive trip in which the conditions for setting
the DTC are met.

Conditions for Clearing the DTC

•

The ECM turns off the MIL after the fourth consecutive drive trip in which the TCM does not send a MIL illumination
request.

•

Tech 2 can clear the DTC.

•

The TCM clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without a non-emission
related diagnostic fault occurring.

•

The TCM cancels the DTC default actions when the ignition is off long enough to power down the TCM.

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