Mitsubishi 380. Manual — part 377

AUTOMATIC TRANSMISSION DIAGNOSIS

AUTOMATIC TRANSMISSION

23A-48

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 data list
item 7: Transmission Fluid Temperature Sensor.

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) Start the engine.
(3) Set diagnostic tool MB991958 to the data reading mode.

• Item 7: Transmission Fluid Temperature Sensor.

• When the engine is cool: Diagnostic tool display is

almost equal to the ambient temperature (atmo-
spheric temperature)

NOTE: Set diagnostic tool MB991958 to the Engine
MPI data list reading mode for item number 5, Intake
Air Temperature (IAT) Sensor and note the tempera-
ture measurement. When the engine is cool, the
temperature should be almost equal to the ambient
temperature (atmospheric temperature), and the IAT
sensor measurement should be approximately the
same as the Transmission Fluid Temperature Sen-
sor.

• When the engine is warm, at approximately running

temperature: 70

− 80°C.

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

Q: Is the sensor 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 Malfunction

P.00-14

.

NO : Go to Step 2.

00DB076A

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

AUTOMATIC TRANSMISSION DIAGNOSIS

AUTOMATIC TRANSMISSION

23A-49

STEP 2. Measure the sensor output voltage at the A/T
control solenoid valve assembly connector B-108 by
backprobing.
(1) Do not disconnect connector B-108.
(2) Turn the ignition switch to the "ON" position.

(3) Measure the voltage between terminal 1 and ground by

backprobing.

• When transmission fluid temperature is 20°C (68°F),

voltage should measure between 3.8 and 4.0 volts.

• When transmission fluid temperature is 40°C (104°F),

voltage should measure between 3.2 and 3.4 volts.

• When transmission fluid temperature is 80°C (176°F),

voltage should measure between 1.7 and 1.9 volts.

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

Q: Is the measured voltage within the specified range?

YES : Go to Step 6.
NO : Go to Step 3.

STEP 3. Check 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 connector and terminals in good condition?

YES : Go to Step 4.
NO : Repair or replace the damaged components. Refer to

GROUP 00E, Harness Connector Inspection

P.00E-2

.

AC306322

CONNECTOR: B-108

B-108 (GR)

AC

TRANSMISSION
RANGE SWITCH

2

7

1

8

3

9

4

6

10

5

5

2

1

7

3

8

4

9

6

10

AC200996

B-108 HARNESS

CONNECTOR:

HARNESS SIDE

AG

AC306322

CONNECTOR: B-108

B-108 (GR)

AC

TRANSMISSION
RANGE SWITCH

2

7

1

8

3

9

4

6

10

5

AUTOMATIC TRANSMISSION DIAGNOSIS

AUTOMATIC TRANSMISSION

23A-50

STEP 4. Check the sensor output voltage at A/T control
solenoid valve assembly connector B-108.
(1) Disconnect connector B-108 and measure at the harness

side.

(2) Turn the ignition switch to the "ON" position.

(3) Measure the voltage between terminal 1 and ground.

• The voltage should measure between 4.5 and 4.9 volts.

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

Q: Is the measured voltage between 4.5 and 4.9 volts?

YES : Go to Step 5.
NO : Go to Step 7.

AC306322

CONNECTOR: B-108

B-108 (GR)

AC

TRANSMISSION
RANGE SWITCH

2

7

1

8

3

9

4

6

10

5

2

5

6

10

4

9

3

8

1

7

AC201006AE

B-108 HARNESS
CONNECTOR:
COMPONENT SIDE

AUTOMATIC TRANSMISSION DIAGNOSIS

AUTOMATIC TRANSMISSION

23A-51

STEP 5. Check the transmission fluid temperature sensor
at A/T control solenoid valve assembly connector B-108.
(1) Disconnect connector B-108 and measure at the sensor

side.

(2) Measure the resistance between terminal 1 and 2.

• When transmission fluid temperature is 0°C (32°F),

resistance should be between 16.7 and 20.5 k

Ω.

• When transmission fluid temperature is 20°C (68°F),

resistance should be between 7.3 and 8.9 k

Ω.

• When transmission fluid temperature is 40°C (104°F),

resistance should be between 3.4 and 4.2 k

Ω.

• When transmission fluid temperature is 60°C (140°F),

resistance should be between 1.9 and 2.2 k

Ω.

• When transmission fluid temperature is 80°C (176°F),

resistance should be between 1.0 and 1.2 k

Ω.

• When transmission fluid temperature is 100°C (212°F),

resistance should be between 0.57 and 0.69 k

Ω.

Q: Is the measured resistance within the specified range?

YES : Go to Step 6.
NO : Replace the transmission fluid temperature sensor.

Refer to GROUP 23B, Transmission

P.23B-13

.

AC306322

CONNECTOR: B-108

B-108 (GR)

AC

TRANSMISSION
RANGE SWITCH

2

7

1

8

3

9

4

6

10

5

2

7

1

8

3

9

4

6

10

5

AC210626AB

B-108 HARNESS
CONNECTOR:
TRANSMISSION FLUID
TEMPERATURE
SENSOR SIDE