Mitsubishi 380. Manual — part 417

AUTOMATIC TRANSMISSION DIAGNOSIS

AUTOMATIC TRANSMISSION

23A-208

CIRCUIT OPERATION

• A/T control relay (terminal 1) receives the battery

positive voltage through a dedicated 20 amp
fuse.

• When the ignition switch is turned to the "ON"

position, the A/T-ECU connector B-22 (terminal
4) receives battery voltage from the ignition
switch. The A/T-ECU connector B-22 (terminal 4)
applies voltage to energize the A/T control relay
(terminal 3). With the A/T control relay energized,
system voltage is applied to the A/T-ECU connec-
tor B-22 (terminals 9 and 3).

.

DTC SET CONDITIONS

Check Conditions

• Voltage of battery: 9 volts or more.

• Time after A/T-ECU turns on A/T control relay:

0.5 second or more.

Judgement Criteria

• A/T control relay output voltage: 7 volts or less.

(0.1 second)

• If (P1751) 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 A/T control relay

• 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 data list
item 8: A/T Control Relay Output Voltage.

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 data reading mode.

• Item 8: A/T Control Relay Output Voltage.

• The voltage should equal battery positive voltage.

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

Q: Is the measured voltage equal battery positive voltage?

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-209

STEP 2. Check the A/T control relay.
(1) Remove the A/T control relay from the engine component

relay box connector B-16X.

(2) Using jumper wires, connect terminal 2 to the positive

battery terminal, and terminal 3 to the negative battery
terminal.

(3) Measure the resistance between terminals 1 and 4 of the

A/T control relay.

• The resistance should be measured less than 2 ohms.

• Disconnect the jumper wires. The resistance between

terminals 1 and 4 should measure over limits (open cir-
cuit).

Q: Is the measured resistance less than 2 ohms when the

relay is energized, and open circuit when the relay is
de-energized?
YES : Go to Step 3.
NO : Replace the A/T control relay.

STEP 3. Check A/T control relay socket B-16X in the
engine compartment relay box for loose, corroded or
damaged terminals, or terminals pushed back in the
socket.
Q: Is the relay connector 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

.

10DB098A

RELAY BOX

CONNECTOR: B-16X

2

1

3 4

FRONT OF
VEHICLE

AC210725

2

1

3 4

AD

B-16X HARNESS CONNECTOR:
A/T CONTROL RELAY SIDE

FRONT OF VEHICLE

10DB098A

RELAY BOX

CONNECTOR: B-16X

2

1

3 4

FRONT OF
VEHICLE

AUTOMATIC TRANSMISSION DIAGNOSIS

AUTOMATIC TRANSMISSION

23A-210

STEP 4. Measure the supply voltage at A/T control relay
connector B-16X in the engine component relay box.
(1) Disconnect the A/T control relay.

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

• The measured voltage should equal battery positive

voltage.

Q: Is the measured voltage equal to battery positive

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

STEP 5. Check intermediate connector A-13 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 6.
NO : Repair or replace the damaged components. Refer to

GROUP 00E, Harness Connector Inspection

P.00E-2

.

STEP 6. Check the harness for open circuit or short circuit
to ground between A/T control relay connector B-16X
terminal 1 in the engine component relay box and battery.
Q: Is the harness wire in good condition?

YES : Go to Step 15.
NO : Repair or replace the harness wire.

10DB098A

RELAY BOX

CONNECTOR: B-16X

2

1

3 4

FRONT OF
VEHICLE

AC210728

1
3

2
4

AC

B-16X HARNESS
CONNECTOR:
RELAY BOX SIDE

FRONT OF
VEHICLE

AC306223

A-13 (GR)

AB

CONNECTOR: A-13

1

4

7

8

2 3

5

13 14

17

15

12

16

11

10

9

6

10DB098A

RELAY BOX

CONNECTOR: B-16X

2

1

3 4

FRONT OF
VEHICLE

AUTOMATIC TRANSMISSION DIAGNOSIS

AUTOMATIC TRANSMISSION

23A-211

STEP 7. Measure the supply voltage at A/T control relay
connector B-16X in the engine component relay box.
(1) Disconnect the A/T control relay.
(2) Turn the ignition switch to the "ON" position.

(3) Measure the voltage between terminal 2 and ground.

• The measured voltage should equal battery positive

voltage.

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

Q: Is the measured voltage equal to battery positive

voltage?
YES : Go to Step 10.
NO : Go to Step 8.

STEP 8. Check intermediate connector A-13 and junction
block connector C-214 for loose, corroded or damaged
terminals, or terminals pushed back in the connector.
Q: Are the connectors in good condition?

YES : Go to Step 9.
NO : Repair or replace the damaged components. Refer to

GROUP 00E, Harness Connector Inspection

P.00E-2

.

10DB098A

RELAY BOX

CONNECTOR: B-16X

2

1

3 4

FRONT OF
VEHICLE

AC210734

1
3

2
4

AC

B-16X HARNESS
CONNECTOR:
RELAY BOX SIDE

FRONT OF
VEHICLE

AC306223

A-13 (GR)

AB

CONNECTOR: A-13

1

4

7

8

2 3

5

13 14

17

15

12

16

11

10

9

6

10DB085A

CONNECTOR: C-214

6

1
7

2

9

8

10

3

5

12

11

4

1314