Isuzu KB P190. Manual - part 1017

7A2-102  TRANSMISSION CONTROL SYSTEM (AW30–40LE) 

 

Circuit/System Testing DTC P1790 

 

Step Action  Value(s) 

YES 

NO 

1 

 

Was the On-Board Diagnostic (OBD) System Check 
performed? 

— Go 

to 

Step 2 

Go to OBD 

System Check

2 

 1. Install a scan tool. 

 2. Turn “OFF” the ignition and keep the position for 

more than 30 seconds. 

 3. Turn “ON” the ignition. 

 4. Check the DTC on a scan tool. 

 

Does a scan tool indicate DTC P1791? 

— Go 

to 

Step 3 

Refer to 

Diagnostic Aids

3 

Perform the SPS for the TCM. 

 

Is the action complete? 

— Go 

to 

Step 4 

— 

4 

Recheck the DTC on the scan tool. 

 

Does the scan tool indicate DTC P1790? 

— Go 

to 

Step 5 

Go to Step 6 

5 

Replace the TCM. 

Important: 

The replacement TCM must be 

programmed (Refer to SPS for procedure). 

 

Is the action complete? 

— Go 

to 

Step 6 — 

6 

 

1. Reconnect all previously disconnected harness 

connector(s). 

 2. Clear the DTCs with a scan tool. 

 3. Turn “OFF” the ignition. 

 4. Start the engine. 

 

5. Operate the vehicle within the Conditions For 

Running the DTC. You may also operate the 
vehicle within the conditions that you observed 
from the Freeze Frame/ Failure Records. 

 

Did the DTC fail this ignition? 

— 

Go to Step 2 Go 

to 

Step 7 

7 

Observe the stored information, Capture info with a 
scan tool. 

 

Are there any DTCs that you have not diagnosed? 

— 

Go to 

Diagnostic 

Trouble Code 

(DTC) List 

Verify repair 

 

TRANSMISSION CONTROL SYSTEM (AW30–40LE)  7A2-103 

 

DTC P1791 (Flash Code 62) 

Description 

DTC P1791 is recorded by TCM when there is
malfunction in the RAM. 

Condition For Running The DTC 

Execute only one time after ignition “ON”. 

Condition For Setting The DTC 

One of the following conditions are met two times
continuously. 

•  Write Ox5a5a5a5a into RAM, and read value is not

same as Ox5a5a5a5a. 

•  Write Oxa5a5a5a5 into RAM, and read value is not

same as Oxa5a5a5a5. 

Action Taken The DTC Sets 

•  Check Trans “ON”. 

• DTC 

stored. 

•  MIL request “ON”. (EURO 4 only) 

Conditions For Clearing The DTC 

•  The DTC can be cleared from the TCM history by

using a scan tool. 

•  The DTC will be cleared from history when the

vehicle has achieved 40 warm-up cycles without a
failure reported. 

•  After more than 1 second has elapsed after the

ignition key has been turned “ON”, short between
No.11 and No.4 (ground) of DLC (Data Link
Connector). Then, after 1 second, but within 6
seconds, discontinue shorting. 

Diagnostic Aids 

•  Inspect the wiring for poor electrical connection at the

TCM. 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. 

 

 

 

 

7A2-104  TRANSMISSION CONTROL SYSTEM (AW30–40LE) 

 

Circuit/System Testing DTC P1791 

 

Step Action  Value(s) 

YES 

NO 

1 

 

Was the On-Board Diagnostic (OBD) System Check 
performed? 

— Go 

to 

Step 2 

Go to OBD 

System Check

2 

 1. Install a scan tool. 

 2. Turn “OFF” the ignition and keep the position for 

more than 30 seconds. 

 3. Turn “ON” the ignition. 

 4. Check the DTC on the scan tool. 

 

Does a scan tool indicate DTC P1791? 

— Go 

to 

Step 3 

Refer to 

Diagnostic Aids

3 

Replace the TCM. 

Important: 

The replacement TCM must be 

programmed (Refer to SPS for procedure). 

 

Is the action complete? 

— Go 

to 

Step 4 — 

4 

 

1. Reconnect all previously disconnected harness 

connector(s). 

 2. Clear the DTCs with a scan tool. 

 3. Turn “OFF” the ignition. 

 4. Start the engine. 

 

5. Operate the vehicle within the Conditions For 

Running the DTC. You may also operate the 
vehicle within the conditions that you observed 
from the Freeze Frame/ Failure Records. 

 

Did the DTC fail this ignition? 

— 

Go to Step 2 Go 

to 

Step 5 

5 

Observe the stored information, Capture info with a 
scan tool. 

 

Are there any DTCs that you have not diagnosed? 

— 

Go to 

Diagnostic 

Trouble Code 

(DTC) List 

Verify repair 

 

TRANSMISSION CONTROL SYSTEM (AW30–40LE)  7A2-105 

 

DTC P2769 or P2770 (Flash Code 33) 

 

 
 

 

 

RTW77ALF001501 

 

Circuit Description 

The lock-up solenoid SL of the torque converter clutch
(TCC) controls the lock-up clutch by a signal according
to the lock-up position judgment of the TCM when the
vehicle runs. 

This function can improve the fuel consumption to 
almost the same extent as the manual transmission.
The lock-up solenoid SL is put into B+ by the TCM, so
that the solenoid is actuated with the result of lock-up. 

 

 

Condition For Running The DTC 

All of the following conditions are met. 

 (1) All of the following conditions are met for 2 

seconds or more continuously. 

•  The supply voltage is more than 10.2 volts and 

less than 15.5 volts. 

  (2) Not emergency mode. 

  (3) 0.025 seconds or more passed after the state of 

energized solenoid is changed.