Mitsubishi Galant. Manual — part 421

AUTOMATIC TRANSAXLE DIAGNOSIS

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AUTOMATIC TRANSAXLE

23A-151

CIRCUIT OPERATION

•

4.8

−

5.2 volt voltage is applied to the vehicle

speed sensor output terminal (terminal 3) from
the PCM (terminal 80). The vehicle speed sensor
generates a pulse signal when the output
terminal is opened and ground.

•

The PCM compares the vehicle speed sensor
signal to input shaft and output shaft speed
sensor signals.

•

If the vehicle speed sensor becomes inoperative,
the transmission will not shift normally.

DTC SET CONDITIONS
If the PCM detects no pulse signal from the vehicle
speed sensor for continuous period of 30 seconds
under following conditions, it is judged as a vehicle
sensor system malfunction and DTC number "29" is
displayed.

•

Driving forward

•

Output shaft speed is 900 r/min or more

TROUBLESHOOTING HINTS (The most likely

causes for this code to be set:)

•

Malfunction of the vehicle speed sensor circuit

•

Damaged harness, connector

•

Malfunction of the PCM

DIAGNOSIS

Required Special Tool:
MB991502: Scan Tool (MUT-II)

STEP 1. Check the speedometer.

Q: Is the speedometer operating properly?

YES : Go to Step 2.
NO : Check the vehicle speed sensor. Refer to GROUP

54A, Combination Meters Assembly and Vehicle
Speed Sensor

−

On-vehicle Service

P.54A-65

.

AC004197

PCM

AC

CONNECTOR: C-41

AC004287

CONNECTOR: C-56

AF

AUTOMATIC TRANSAXLE DIAGNOSIS

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STEP 2. Using scan tool MB991502, check data list item 29:
Vehicle Speed Sensor.

CAUTION

To prevent damage to scan tool MB991502, always turn the
ignition switch to "LOCK" (OFF) position before
connecting or disconnecting scan tool MB991502.
(1) Connect scan tool MB991502 to the data link connector.
(2) Start the engine.
(3) Set scan tool MB991502 to data reading mode for item 29:

Vehicle Speed Sensor.

•

Check that the speedometer and MUT-II display speed
match when driving at a vehicle speed of 40 km/h (25
mph).

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

Q: Is the sensor operating properly?

YES : This malfunction is intermittent. Refer to GROUP 00,

How to Use Troubleshooting/Inspection Service
Points

−

How to Cope with Intermittent Malfunction

P.00-8

.

NO : Go to Step 3.

AC003081AC

MB991502

DATA LINK
CONNECTOR

AUTOMATIC TRANSAXLE DIAGNOSIS

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STEP 3. Using the oscilloscope, check the waveform at
PCM connector C-41.
(1) Do not disconnect connector C-41.

(2) Connect an oscilloscope probe to PCM connector C-41

terminal 80 by backprobing.

(3) Start the engine.

(4) Check the waveform.

•

The waveform should show a pattern similar to the
illustration when running the vehicle.

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

Q: Is the waveform normal?

YES : Go to Step 5.
NO : Go to Step 4.

AC004197

PCM

AC

CONNECTOR: C-41

AC001954

OSCILLO-
SCOPE

PROBE

C-41 CONNECTOR
HARNESS SIDE VIEW

AE

ACX02131

NORMAL WAVEFORM

(V)

AC

AUTOMATIC TRANSAXLE DIAGNOSIS

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STEP 4. Check connectors C-41 at PCM and C-17 at
intermediate connector for damage.
Q: Are the connectors in good condition?

YES : Repair it because of harness open circuit or damage

between PCM connector C-41 terminal 80 and
intermediate connector C-17 terminal 3.

NO : Repair or replace it. Refer to GROUP 00E, Harness

Connector Inspection

P.00E-2

.

STEP 5. Check connector C-41 at PCM for damage.
Q: Is the connector in good condition?

YES : Go to Step 6.
NO : Repair or replace it. Refer to GROUP 00E, Harness

Connector Inspection

P.00E-2

.

AC004197

PCM

AC

CONNECTOR: C-41

AC004308AB

CONNECTOR: C-17

AC004197

PCM

AC

CONNECTOR: C-41