Mitsubishi Eclipse. Manual - part 772

AUTOMATIC TRANSAXLE DIAGNOSIS

TSB Revision

AUTOMATIC TRANSAXLE

23A-97

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CIRCUIT OPERATION
The crankshaft position sensor power is supplied 
from the MFI relay (terminal 4) to the crankshaft posi-
tion sensor (terminal 3). The crankshaft position sen-
sor (terminal 1) is grounded by the PCM (terminal 
16). The PCM (terminal 45) supplies 5 volts to the 
crankshaft position sensor output (terminal 2). The 
crankshaft position sensor detects the crank angle 
(position) of each cylinder, and converts that data to 
pulse signals that are sent to the PCM.

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DTC SET CONDITIONS
If the crankshaft position sensor does not detect an 
output pulse for more than 5 seconds while driving 
more than 25 km/h (16 mph), it is judged that there is 
an open circuit in the crankshaft position sensor and 
DTC 21 is set.

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TROUBLESHOOTING HINTS (The most likely 
causes for this code to be set are:)

• Malfunction of the crankshaft position sensor cir-

cuit

• Damaged harness or 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

AC004927AC

CONNECTOR: B-20
<3.0L ENGINE>

B-20

AC001729AY

CONNECTOR: C-07

C-07

AC001657

CONNECTORS:  C-50 <2.4L ENGINE>  OR
C-52 <3.0L ENGINE>, C-54 <2.4L ENGINE> 
OR C-55 <3.0L ENGINE>

PCM

BF

C-50 <2.4L ENGINE> OR 
C-52 <3.0L ENGINE>

C-54 <2.4L ENGINE> OR 
C-55 <3.0L ENGINE>

AUTOMATIC TRANSAXLE DIAGNOSIS

TSB Revision

AUTOMATIC TRANSAXLE

23A-98

STEP 1. Using scan tool MB991958, check data list item 21: 
Crankshaft Position Sensor.

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) With the gear selector lever in the "P" position, start the 

engine and run at idle.

(3) Set scan tool MB991958 to data reading mode for item 21: 

Crankshaft Position Sensor.

• When the accelerator pedal is not depressed (throttle 

valve is fully closed) the display on the scan tool 
MB991958 should be "600 to 900 r/min."

• With the accelerator pedal depressed, the engine speed 

display on the scan tool MB991958 should increase 
according to engine speed.

Q: Does the engine speed display increase according to 

engine speed when the accelerator pedal is depressed?
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 2.

AC303127

AB

MB991911

16-PIN

MB991827

MB991824 

AUTOMATIC TRANSAXLE DIAGNOSIS

TSB Revision

AUTOMATIC TRANSAXLE

23A-99

STEP 2. Using the oscilloscope, check the waveform at 
crankshaft position sensor connector B-20.
(1) Do not disconnect connector B-20.

(2) Connect an oscilloscope probe between crankshaft position 

sensor connector B-20 terminal 2 and ground by 
backprobing.

(3) With the gear selector lever in the "P" position, start the 

engine and run at idle.

AC004926AC

CONNECTOR: B-20
<2.4L ENGINE>

B-20

AC004927AC

CONNECTOR: B-20
<3.0L ENGINE>

B-20

AC001805AL

B-20 HARNESS
CONNECTOR:
HARNESS SIDE

OSCILLOSCOPE

AUTOMATIC TRANSAXLE DIAGNOSIS

TSB Revision

AUTOMATIC TRANSAXLE

23A-100

(4) Check the waveform.

• The waveform should show a pattern similar to the illus-

tration. The maximum value should be 4.8 volts or more 
and the minimum value 0.6 volt or 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 3.
NO :  Go to Step 5.

AC002215AB

NORMAL WAVEFORM

<2.4L ENGINE>

5 V

2 ENGINE REVOLUTIONS

2 ENGINE REVOLUTIONS

<3.0L ENGINE>

5 V