Mitsubishi 380. Manual - part 414

AUTOMATIC TRANSMISSION DIAGNOSIS

AUTOMATIC TRANSMISSION

23A-196

(P0731): 1st Gear Incorrect Ratio
(P0732): 2nd Gear Incorrect Ratio
(P0733): 3rd Gear Incorrect Ratio
(P0734): 4th Gear Incorrect Ratio
(P0735): 5th Gear Incorrect Ratio
(P0736): Reverse Gear Incorrect Ratio

CIRCUIT OPERATION

• The input shaft speed sensor generates a pulsed

signal of 0

⇔ 5 volts. The pulsed signal fre-

quency increases with an increase in the input
shaft speed.

• The A/T-ECU continuously monitors the input

shaft speed signal.

• The output shaft speed sensor generates a

pulsed signal of 0

⇔ 5 volts. The pulsed signal

frequency increases with an increase in the out-
put shaft speed.

• The A/T-ECU continuously monitors the output

shaft speed signal.

DTC SET CONDITIONS < (P0731)>

Check Conditions

• Engine speed: 450 r/min or more.

• Output speed: 350 r/min or more.

• Shift stage: 1st gear.

• Input speed: more than 0 r/min.

• Transmission fluid temperature sensor voltage:

4.5 volts or less.

• Voltage of battery: 10 volts or more.

• Transmission inhibitor switch rationality: only one

signal.

• Time after shift changing finish: 2 seconds or

more.

Judgement Criteria

• Output speed: [(input speed - 200 r/min) / 1st

gear ratio] or less. (4 seconds)

• If (P0731) 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 <
(P0731)>

Start the engine, and drive at 20 km/h (12 mph) or
more for 10 seconds, with 1st gear fixed (1st gear in
sport mode).

DTC SET CONDITIONS < (P0732)>

Check Conditions

• Engine speed: 450 r/min or more.

• Output speed: 500 r/min or more.

• Shift stage: 2nd gear.

• Input speed: more than 0 r/min.

• Transmission fluid temperature sensor voltage:

4.5 volts or less.

• Voltage of battery: 10 volts or more.

• Transmission inhibitor switch rationality: only one

signal.

• Time after shift changing finish: 2 seconds or

more.

Judgement Criteria

• Output speed: [(input speed + 200 r/min) / 2nd

gear ratio] or more. (4 seconds)

• Output speed: [(input speed - 200 r/min) / 2nd

gear ratio] or less. (4 seconds)

• If (P0732) 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 <
(P0732)>

Start the engine, and drive at 30 km/h (19 mph) or
more for 10 seconds, with 2nd gear fixed (2nd gear
in sport mode).

AUTOMATIC TRANSMISSION DIAGNOSIS

AUTOMATIC TRANSMISSION

23A-197

DTC SET CONDITIONS < (P0733)>

Check Conditions

• Engine speed: 450 r/min or more.

• Output speed: 900 r/min or more.

• Shift stage: 3rd gear.

• Input speed: more than 0 r/min.

• Transmission fluid temperature sensor voltage:

4.5 volts or less.

• Voltage of battery: 10 volts or more.

• Transmission inhibitor switch rationality: only one

signal.

• Time after shift changing finish: 2 seconds or

more.

Judgement Criteria

• Output speed: [(input speed + 200 r/min) / 3rd

gear ratio] or more. (4 seconds)

• Output speed: [(input speed - 200 r/min) / 3rd

gear ratio] or less. (4 seconds)

• If (P0733) 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 <
(P0733)>

Start the engine, and drive at 40 km/h (25 mph) or
more for 10 seconds, with 3rd gear fixed (3rd gear in
sport mode).

DTC SET CONDITIONS < (P0734)>

Check Conditions

• Engine speed: 450 r/min or more.

• Output speed: 900 r/min or more.

• Shift stage: 4th gear.

• Input speed: more than 0 r/min.

• Transmission fluid temperature sensor voltage:

4.5 volts or less.

• Voltage of battery: 10 volts or more.

• Transmission inhibitor switch rationality: only one

signal.

• Time after shift changing finish: 2 seconds or

more.

Judgement Criteria

• Output speed: [(input speed + 200 r/min) / 4th

gear ratio] or more. (4 seconds)

• Output speed: [(input speed - 200 r/min) / 4th

gear ratio] or less. (4 seconds)

• If (P0734) 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 <
(P0734)>

Start the engine, and drive at 40 km/h (25 mph) or
more for 10 seconds, with 4th gear fixed (4th gear in
sport mode).

DTC SET CONDITIONS < (P0735)>

Check Conditions

• Engine speed: 450 r/min or more.

• Output speed: 900 r/min or more.

• Shift stage: 5th gear.

• Input speed: more than 0 r/min.

• Transmission fluid temperature sensor voltage:

4.5 volts or less.

• Voltage of battery: 10 volts or more.

• Transmission inhibitor switch rationality: only one

signal.

• Time after shift changing finish: 2 seconds or

more.

Judgement Criteria

• Output speed: [(input speed + 200 r/min) / 4th

gear ratio] or more. (4 seconds)

• Output speed: [(input speed - 200 r/min) / 4th

gear ratio] or less. (4 seconds)

• If (P0735) 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 <
(P0735)>

Start the engine, and drive at 40 km/h (25 mph) or
more for 10 seconds, with 5th gear fixed (5th gear in
sport mode).

AUTOMATIC TRANSMISSION DIAGNOSIS

AUTOMATIC TRANSMISSION

23A-198

DTC SET CONDITIONS < (P0736)>

Check Conditions

• Engine speed: 450 r/min or more.

• Output speed: 100 r/min or more.

• Shift stage: reverse gear.

• Input speed: more than 0 r/min.

• Transmission fluid temperature sensor voltage:

4.5 volts or less.

• Voltage of battery: 10 volts or more.

• Transmission inhibitor switch rationality: only one

signal.

• Time after shift changing finish: 0.5 second or

more.

Judgement Criteria

• Output speed: [(input speed + 200 r/min) /

reverse gear ratio] or more. (1 second)

• Output speed: [(input speed - 200 r/min) / reverse

gear ratio] or less. (1 second)

• If (P0736) 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 <
(P0736)>

Start the engine, and drive in "R" range at 15 km/h (9
mph) or more for 10 seconds.

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

• Malfunction of the input shaft speed sensor

• Malfunction of the output shaft speed sensor

• Malfunction of the A/T-ECU

• Malfunction of the underdrive clutch retainer

• Malfunction of the transfer drive gear or driven

gear

• Malfunction of the low-reverse brake system ( or )

• Malfunction of the underdrive clutch system (, , or

)

• Malfunction of the second brake system ( or )

• Malfunction of the overdrive clutch system ( or )

• Malfunction of the reduction clutch system ( or )

• Malfunction of the reverse clutch system ()

• Electrical noise generated

Circuit drawings

• Refer to circuit diagrams GROUP-

• Refer to configuration diagrams GROUP-

• Refer to component locations GROUP-

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

AUTOMATIC TRANSMISSION DIAGNOSIS

AUTOMATIC TRANSMISSION

23A-199

STEP 1. Using diagnostic tool MB991958, read the A/T
diagnostic trouble code.

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

Q: Is DTC set?

YES <P0715 set> : Refer to

P.23A-55

, P0715: Input Shaft

Speed Sensor System.

YES <P0720 set> : Refer to

P.23A-72

, P0720: Output Shaft

Speed Sensor System.

YES <P0753 set> : Refer to

P.23A-133

, P0753: