Mitsubishi Galant. Manual — part 447

AUTOMATIC TRANSAXLE DIAGNOSIS

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AUTOMATIC TRANSAXLE

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INSPECTION PROCEDURE 16: Transaxle won't Downshift under Load with Auto-cruise Engaged.

CIRCUIT OPERATION
When the battery positive voltage from PCM
(terminal number 75) is grounded at auto-cruise
control-ECU (terminal number 3), the auto-cruise
control-ECU emits a overdrive cancel signal. When a

malfunction of the auto-cruise control circuit occurs,
the transmission may downshift harshly with the
auto-cruise control engaged.

AC004623

Auto-cruise Signal Line System Circuit

AB

AC004308AB

CONNECTOR: C-17

AC004197

PCM

AC

CONNECTOR: C-41

AC004376

CONNECTOR: C-52

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AUTOMATIC TRANSAXLE DIAGNOSIS

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COMMENT
A malfunction may be present on the auto-cruise
signal line circuit, auto-cruise control ECU or the
PCM.

TROUBLESHOOTING HINTS (The most likely

causes for this code to be set:)

•

Damaged harness, connector

•

Malfunction of the PCM

•

Malfunction of the auto-cruise control ECU

DIAGNOSIS

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

STEP 1. Using scan tool MB991502, check data list item 66:
Overdrive Off Signal (Auto-cruise ECM Signal).

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. (Operate the auto-cruise)
(3) Set scan tool MB991502 to data reading mode for item 66:

Overdrive Off Signal (Auto-cruise ECM Signal).

•

When driving at level road, the display should be "OFF."

•

When driving at uphill road, the display should be "ON."

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

Q: Is the sensor operating properly?

YES : This malfunction can be 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 2.

STEP 2. Check the auto-cruise system.
Check the auto-cruise system. Refer to GROUP 17, Auto-
cruise Control System Diagnostic Troubleshooting Strategy

P.17-7

.

Q: Is the auto-cruise system operating properly?

YES : Go to Step 3.
NO : Repair it, then check the symptom.

AC003081AC

MB991502

DATA LINK
CONNECTOR

AUTOMATIC TRANSAXLE DIAGNOSIS

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STEP 3. Check the signal voltage at PCM connector C-41
by backprobing.
(1) Do not disconnect connector C-41.
(2) Turn the ignition switch to "ON" position.

(3) Measure the voltage between terminal 75 and ground by

backprobing.

•

Voltage should be battery positive voltage.

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

Q: Is the voltage normal?

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

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

YES : Replace the PCM.
NO : Repair or replace it. Refer to GROUP 00E, Harness

Connector Inspection

P.00E-2

.

AC004197

PCM

AC

CONNECTOR: C-41

AC002097

C-41 CONNECTOR
HARNESS SIDE VIEW

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AC004197

PCM

AC

CONNECTOR: C-41

AC004308AB

CONNECTOR: C-17

AUTOMATIC TRANSAXLE DIAGNOSIS

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STEP 5. Check the signal voltage at auto-cruise control-
ECU connector C-52 by backprobing.
(1) Do not disconnect connector C-52.
(2) Turn the ignition switch to "ON" position.

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

backprobing.

•

Voltage should be battery positive voltage.

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

Q: Is the voltage normal?

YES : Go to Step 7.
NO : Go to Step 6.

STEP 6. Check harness for short circuit to ground, open
circuit or damage between PCM connector C-41 terminal
75 and auto-cruise control-ECU connector C-52 terminal 3.
Q: Is the harness wire in good condition?

YES : Go to Step 7.
NO : Repair it.

AC004376

CONNECTOR: C-52

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AC002119

C-52 CONNECTOR
HARNESS SIDE VIEW

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AC004197

PCM

AC

CONNECTOR: C-41

AC004376

CONNECTOR: C-52

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