Mitsubishi Eclipse. Manual — part 836

AUTOMATIC TRANSAXLE DIAGNOSIS

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AUTOMATIC TRANSAXLE

23A-353

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CIRCUIT OPERATION

• While the vehicle is being driven, the PCM sends

pulse signals (ranging from 0 to 12 volts) to the
combination meter according to output signals
from the output shaft speed sensor. The combi-
nation meter displays vehicle speed according to
the pulse signals.

• If the vehicle speed signal becomes inoperative,

the transaxle will not shift normally.

.

COMMENT
Failure may occur on vehicle speed signal circuit,
speedometer and PCM.

.

TROUBLESHOOTING HINTS (The most likely
causes for this case:)

• Malfunction of the output shaft speed sensor

• Malfunction of the speedometer

• Damaged harness, connector

• Malfunction of the PCM

DIAGNOSIS

Required Special Tool:

• MB991958: Scan Tool (MUT-III Sub Assembly)

• MB991824: V.C.I.

• MB991827: MUT-III USB Cable

• MB991911: MUT-III Main Harness B

AC106611AB

CONNECTOR: C-28

C-28

AC001729 BB

CONNECTOR: C-42

C-42

AC001657

CONNECTOR: C-57 <2.4L ENGINE> OR
C-59 <3.0L ENGINE>

AZ

PCM

C-57 <2.4L ENGINE> OR C-59 <3.0L ENGINE>

AC001729 BA

CONNECTOR: C-77

C-77

AUTOMATIC TRANSAXLE DIAGNOSIS

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AUTOMATIC TRANSAXLE

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

CAUTION

To prevent damage to scan tool MB991958, always turn the
ignition switch to the "LOCK" (OFF) position before con-
necting or disconnecting scan tool MB991958.
(1) Connect scan 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 23 set?

YES : Refer to

P.23A-131

, DTC 23: Output Shaft Speed

Sensor System.

NO : Go to Step 2.

STEP 2. Using scan tool MB991958, check data list item 29:
Vehicle Speed Signal.
(1) Connect scan tool MB991958 to the data link connector.
(2) Start the engine.
(3) Set scan tool MB991958 to data reading mode for item 29:

Vehicle Speed Signal.

• Check that the speedometer and scan tool MB991958

display speed match when driving at a vehicle speed of
40 km/h (25 mph).

(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.00-6

.

NO : Go to Step 3.

AC303127

AB

MB991911

16-PIN

MB991827

MB991824

AC303127

AB

MB991911

16-PIN

MB991827

MB991824

AUTOMATIC TRANSAXLE DIAGNOSIS

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AUTOMATIC TRANSAXLE

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STEP 3. Using an oscilloscope, check the vehicle speed
signal waveform at PCM connector C-57 <2.4L Engine> or
C-59 <3.0L Engine> by backprobing.
(1) Do not disconnect connector C-57 <2.4L Engine> or C-59

<3.0L Engine>.

(2) Connect an oscilloscope probe to PCM connector C-57

<2.4L Engine> or C-59 <3.0L Engine> terminal 80 by
backprobing.

(3) Start the engine and drive the vehicle.

(4) Check the vehicle speed signal waveform.

• The vehicle speed signal waveform should show a pat-

tern similar to the illustration. The maximum value
should be 11 volts and more and the minimum value 0.6
volt and less. The output waveform should not contain
electrical noise

(5) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the waveform normal?

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

STEP 4. Check PCM connector C-57 <2.4L Engine> or C-59
<3.0L Engine> 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 8.
NO : Repair or replace the damaged components. Refer to

GROUP 00E, Harness Connector Inspection

P.00E-2

.

AC001657

CONNECTOR: C-57 <2.4L ENGINE> OR
C-59 <3.0L ENGINE>

AZ

PCM

C-57 <2.4L ENGINE> OR C-59 <3.0L ENGINE>

AC001954

OSCILLO-
SCOPE

PROBE

C-57 <2.4L ENGINE> OR
C-59 <3.0L ENGINE> HARNESS
CONNECTOR: HARNESS SIDE

AN

AC102347AB

NORMAL WAVEFORM

(V)

0

12

(ms)

AC001657

CONNECTOR: C-57 <2.4L ENGINE> OR
C-59 <3.0L ENGINE>

AZ

PCM

C-57 <2.4L ENGINE> OR C-59 <3.0L ENGINE>

AUTOMATIC TRANSAXLE DIAGNOSIS

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AUTOMATIC TRANSAXLE

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STEP 5. Check PCM connector C-57 <2.4L Engine> or C-59
<3.0L Engine>, intermediate connector C-28, joint
connector C-77 and combination meter connector C-42 for
loose, corroded or damaged terminals, or terminals
pushed back in the connector.
Q: Are the connectors 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

.

AC001657

CONNECTOR: C-57 <2.4L ENGINE> OR
C-59 <3.0L ENGINE>

AZ

PCM

C-57 <2.4L ENGINE> OR C-59 <3.0L ENGINE>

AC106611AB

CONNECTOR: C-28

C-28

AC001729 BA

CONNECTOR: C-77

C-77