Mitsubishi 380. Manual - part 401

AUTOMATIC TRANSMISSION DIAGNOSIS

AUTOMATIC TRANSMISSION

23A-144

(P0758): Underdrive Solenoid Valve System

.

SOLENOID VALVE SYSTEM CIRCUIT

 Refer to 

P.23A-133

.

.

CIRCUIT OPERATION

 Refer to 

P.23A-133

.

.

DTC SET CONDITIONS

Check Conditions

• Solenoid status: either solid ON or OFF.

• Shift status: in-gear.

• Voltage of battery: 10 volts or more.

Judgement Criteria

• Solenoid voltage: 3 volts or less. (0.3 second)

• If (P0758) is set consecutively four times, the 

transmission is locked into 3rd gear as a fail-safe 
measure, and the "N" range light flashes once 
per second.

.

OBD-II DRIVE CYCLE PATTERN

Start the engine, and keep the vehicle stopped in "P" 
range for 5 seconds.

.

TROUBLESHOOTING HINTS (THE MOST 
LIKELY CAUSES FOR THIS CODE TO BE 
SET ARE:)

• Malfunction of the underdrive solenoid valve

• Damaged harness or connector

• Malfunction of the A/T-ECU

Circuit drawings

• Refer to circuit diagrams GROUP-

90

• Refer to configuration diagrams GROUP-

80

• Refer to component locations GROUP-

70

DIAGNOSIS

Required Special Tool:

• MB991958: Diagnostic Tool (MUT-III Sub Assembly)

• MB991824: V.C.I.

• MB991827: MUT-III USB Cable

• MB991910: MUT-III Main Harness A

STEP 1. Using diagnostic tool MB991958, check actuator 
test item 02: Underdrive Solenoid Valve.

CAUTION

To prevent damage to diagnostic tool MB991958, always 
turn the ignition switch to the "LOCK" (OFF) position 
before connecting or disconnecting diagnostic tool 
MB991958.
(1) Connect diagnostic tool MB991958 to the data link 

connector.

(2) Turn the ignition switch to the "ON" position.
(3) Set diagnostic tool MB991958 to the actuator test mode.

• Item 02: Underdrive Solenoid Valve.

• An audible clicking or buzzing should be heard when 

the underdrive solenoid valve is energized.

(4) Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the solenoid valve operating properly?

YES : It can be assumed that this malfunction is intermittent. 

Refer to GROUP 00, How to Use 
Troubleshooting/Inspection Service Points 

− How to 

Cope with Intermittent Malfunctions 

P.00-14

.

NO :  Go to Step 2.

00DB076A

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

AUTOMATIC TRANSMISSION DIAGNOSIS

AUTOMATIC TRANSMISSION

23A-145

STEP 2. Using diagnostic tool MB991958, read the A/T 
diagnostic trouble code.
(1) Connect diagnostic tool MB991958 to the data link 

connector.

(2) Turn the ignition switch to the "ON" position.
(3) Check for A/T diagnostic trouble code.
(4) Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is (P1751) set? (P1751 may be set along with multiple 

DTCs).
YES : Refer to 

P.23A-207

 (P1751): A/T Control Relay 

System.

NO :  Go to Step 3.

STEP 3. Using diagnostic tool MB991958, read the A/T 
diagnostic trouble code.
(1) Connect diagnostic tool MB991958 to the data link 

connector.

(2) Turn the ignition switch to the "ON" position.
(3) Check for A/T diagnostic trouble code.
(4) Turn the ignition switch to the "LOCK" (OFF) position.

Q: Are (P0763) and (P0768) set? (Multiple DTCs may be 

set).
YES : Go to Step 8.
NO :  Go to Step 4.

00DB076A

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

00DB076A

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

AUTOMATIC TRANSMISSION DIAGNOSIS

AUTOMATIC TRANSMISSION

23A-146

STEP 4. Measure the underdrive solenoid valve resistance 
at A/T control solenoid valve assembly connector B-108.
(1) Disconnect connector B-108 and measure at the solenoid 

valve side.

(2) Measure the resistance between solenoid valve assembly 

connector B-108 terminals 3 and 9.

Resistance value: 2.7

−3.4 Ω [at 20°C (68°F)]

Q: Is the measured resistance 2.7

−3.4 Ω [at 20°C (68°F)]?

YES : Go to Step 6.
NO :  Go to Step 5.

STEP 5. Measure the solenoid valve resistance at the 
underdrive solenoid valve assembly inside the 
transmission.
(1) Disconnect connector B-108-1 and measure at the solenoid 

valve side.

(2) Measure the resistance between Underdrive solenoid valve 

terminals 1 and 2.

Resistance value: 2.7

−3.4 Ω [at 20°C (68°F)]

Q: Is the measured resistance 2.7

−3.4 Ω [at 20°C (68°F)?

YES : Replace the harness wire between A/T control 

solenoid valve assembly connector B-108 and the 
solenoid valves.

NO :  Replace the Underdrive solenoid valve. Refer to 

GROUP 23B, Valve Body 

23B-62

.

AC306322

CONNECTOR: B-108

B-108 (GR)

AC

TRANSMISSION
RANGE SWITCH

2

7

1

8

3

9

4

6

10

5

AC210677

2

7

1

8

3

9

4

6

10

5

AB

B-108 HARNESS CONNECTOR: 
A/T CONTROL SOLENOID VALVE 
ASSEMBLY SIDE

VALVE BODY
ASSEMBLY

10DB109A

CONNECTORS:  B-108-1     

B-108-1

2

1

AC201141

B-108-1 HARNESS CONNECTOR: 
UNDERDRIVE 
SOLENOID VALVE SIDE

BA

AUTOMATIC TRANSMISSION DIAGNOSIS

AUTOMATIC TRANSMISSION

23A-147

STEP 6. Check A/T-ECU connector B-22 and A/T control 
solenoid valve assembly connector B-108 for loose, 
corroded or damaged terminals, or terminals pushed back 
in the connector.
Q: Are the connectors and terminals in good condition?

YES : Go to Step 7.
NO :  Repair or replace the damaged components. Refer to 

GROUP 00E, Harness Connector Inspection 

P.00E-2

.

16DB564A

COVER

AIR

CLEANER

A/T

CONTROL

UNIT

CONNECTORS:  B-19, B-22

AC306322

CONNECTOR: B-108

B-108 (GR)

AC

TRANSMISSION
RANGE SWITCH

2

7

1

8

3

9

4

6

10

5