Mitsubishi Evolution X. Manual - part 1281

AUTO A/C DIAGNOSIS

TSB Revision

HEATER, AIR CONDITIONING AND VENTILATION

55-75

TECHNICAL DESCRIPTION (COMMENT)

The A/C-ECU power system may be defective if the air condi-
tioning, defogger, and outside/inside air selection damper 
motor all do not operate normally.

.

TROUBLESHOOTING HINTS

• Malfunction of the A/C-ECU

• Damaged harness wires or connectors

DIAGNOSIS

Required Special Tool:

• MB991223: Test Harness Set

STEP 1. Check A/C-ECU connector C-22 for loose, 
corroded or damaged terminals, or terminals pushed back 
in the connector.
Q:  Is A/C-ECU connector C-22 in good condition?

YES : Go to Step 2.
NO :  Repair or replace the connector. Refer to GROUP 

00E, Harness Connector Inspection 

P.00E-2

. Check 

that the A/C works normally.

STEP 2. Measure the voltage at A/C-ECU connector C-22. 
(1) Disconnect A/C-ECU connector C-22 and measure the 

voltage at the harness side.

(2) Turn the ignition switch to the "ON" position.
(3) Measure the voltage between terminal 15 and ground.

• The measured value should be approximately 12 volts 

(battery positive voltage).

Q: Is the measured voltage approximately 12 volts?

YES :  Go to Step 5.
NO :   Go to Step 3.

STEP 3. Check ETACS-ECU connector C-317 for loose, 
corroded or damaged terminals, or terminals pushed back 
in the connector.
Q:  Is ETACS-ECU connector C-317 in good condition?

YES : Go to Step 4.
NO :  Repair or replace the connector. Refer to GROUP 

00E, Harness Connector Inspection 

P.00E-2

. Check 

that the A/C works normally.

AC608254 CJ

Connector C-22
(Harness side)

AUTO A/C DIAGNOSIS

TSB Revision

HEATER, AIR CONDITIONING AND VENTILATION

55-76

STEP 4. Check the wiring harness between A/C-ECU 
connector C-22 (terminal 15) and ETACS-ECU connector 
C-317 (terminal 5).
Q: Is the wiring harness between A/C-ECU connector C-22 

(terminal 15) and ETACS-ECU connector C-317 (terminal 
5) in good condition?
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 Malfunctions 

P.00-15

.

NO :  Repair the wiring harness. Check that the A/C works 

normally.

STEP 5. Measure the voltage at A/C-ECU connector C-22. 
(1) Disconnect A/C-ECU connector C-22 and measure the 

voltage at the harness side.

(2) Measure the voltage between terminal 13 and ground.

• The measured value should be approximately 12 volts 

(battery positive voltage).

Q: Is the measured voltage approximately 12 V?

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

STEP 6. Check the wiring harness between A/C-ECU 
connector C-22 (terminal 13) and the FUSIBLE LINK (36).
NOTE: Also check ETACS-ECU connector C-317 for loose, 
corroded, or damaged terminals, or terminals pushed back in 
the connector. If ETACS-ECU connector C-317 is damaged, 
repair or replace the connector as described in GROUP 00E, 
Harness Connector Inspection 

P.00E-2

.

Q: Is the wiring harness between A/C-ECU connector C-22 

(terminal 13) and the FUSIBLE LINK (36) in good 
condition?
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 Malfunctions 

P.00-15

.

NO :  Repair the wiring harness. Check that the A/C works 

normally.

AC608254 CK

Connector C-22
(Harness side)

AUTO A/C DIAGNOSIS

TSB Revision

HEATER, AIR CONDITIONING AND VENTILATION

55-77

STEP 7. Measure the resistance at A/C-ECU connector 
C-22.
(1) Disconnect A/C-ECU connector C-22, and measure at the 

wiring harness side.

(2) Measure the resistance between terminal 14 and ground.

• The measured value should be 2 ohms or less.

Q: Does the measured resistance value correspond with 

this range?
YES : Replace the A/C-ECU, and check that the A/C works 

normally.

NO :   Go to Step 8.

STEP 8. Check the wiring harness between A/C-ECU 
connector C-22 (terminal 14) and the ground.
Q: Is the wiring harness between A/C-ECU connector C-22 

(terminal 14) and ground in good condition?
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 Malfunctions 

P.00-15

.

NO :  Repair the wiring harness. Check that the A/C works 

normally.

AC608255 BR

Connector C-22
(Harness side)

AUTO A/C DIAGNOSIS

TSB Revision

HEATER, AIR CONDITIONING AND VENTILATION

55-78

INSPECTION PROCEDURE 3: The Compressor does not Work.

A/C Compressor Assembly Circuit

A/C
COMPRESSOR
CLUTCH RELAY

A/C
COMPRESSOR
ASSEMBLY

A/C
REFRIGERANT
TEMPERATURE
SWITCH

A/C
COMPRESSOR
CLUTCH

ENGINE CONTROL MODULE

RELAY
BOX

FUSIBLE
LINK

36

AC708618