Mitsubishi Evolution X. Manual - part 1265

AUTO A/C DIAGNOSIS

TSB Revision

HEATER, AIR CONDITIONING AND VENTILATION

55-11

Past trouble

• If DTC B10C0 or B10C1 is stored as a past trouble, carry 

out diagnosis with particular emphasis on wiring and con-
nector(s) between the A/C-ECU and the interior tempera-
ture sensor. If the connectors and wiring are normal, and 
obviously the ECU is the cause of the trouble, replace the 
ECU. If in doubt, do not replace the ECU.

.

TROUBLESHOOTING HINT

• Malfunction of connector.

• Malfunction of the harness.

• Malfunction of the interior temperature sensor.

• Malfunction of the A/C-ECU.

DIAGNOSIS

Required Special Tool:

•  MB991958: Scan Tool (M.U.T.-III Sub Assembly)

• MB991824: Vehicle Communication Interface (V.C.I.)

• MB991827: M.U.T.-III USB Cable

• MB991910: M.U.T.-III Main Harness A

STEP 1. Using scan tool MB991958, diagnose the CAN bus 
line.

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.
Use scan tool MB991958 to diagnose the CAN bus lines.
(1) Connect scan tool MB991958. Refer to "How to connect the 

Scan Tool (M.U.T.-III) 

P.55-7

."

(2) Turn the ignition switch to "ON" position.
(3) Diagnose the CAN bus line.
Q: Is the check result satisfactory?

YES : Go to Step 2.
NO :  Repair the CAN bus lines. Repair the CAN bus lines 

(Refer to GROUP 54C, Diagnosis-Can Bus 
Diagnostic Chart 

P.54C-14

).

STEP 2. Recheck for diagnostic trouble code.
Recheck if the DTC is set.
(1) Erase the DTC.
(2) Turn the ignition switch to "ON" position.
(3) Check if the DTC is set.
Q: Is the check result satisfactory?

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 :  Go to Step 3. 

AUTO A/C DIAGNOSIS

TSB Revision

HEATER, AIR CONDITIONING AND VENTILATION

55-12

STEP 3. Check interior temperature sensor connector C-06 
and A/C-ECU connector C-22 for loose, corroded or 
damaged terminals, or terminals pushed back in the 
connector.
Q: Are interior temperature sensor connector C-06 and 

A/C-ECU connector C-22 in good condition?
YES : Go to Step 4.
NO :  Repair or replace the connector. Refer to GROUP 

00E, Harness Connector Inspection 

P.00E-2

.

STEP 4. Check the wiring harness between A/C-ECU 
connector C-22 (terminal 17 and 19) and interior 
temperature sensor connector C-06 (terminals 1 and 2).
NOTE: Also check joint connector C-102 for loose, corroded, or 
damaged terminals, or terminals pushed back in the connector. 
If joint connector C-102 is damaged, repair or replace the con-
nector as described in GROUP 00E, Harness Connector 
Inspection 

P.00E-2

.

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

(terminal 17 and 19) and interior temperature sensor 
connector C-06 (terminals 1 and 2) in good condition?
YES : Go to Step 5.
NO :  Repair the wiring harness.

STEP 5. Check the interior temperature sensor.
Measure the resistance between connector terminals 1 and 2 
under at least two different temperatures. The resistance val-
ues should generally match those in the graph. 
NOTE: The temperature at the check should not exceed the 
range in the graph. 
Q: Is the interior temperature sensor in good condition?

YES : Replace the A/C-ECU. Then go to Step 6.
NO :  Replace the interior temperature sensor. Then go to 

Step 6.

STEP 6. Recheck for diagnostic trouble code.
Check again if the DTC is set.
(1) Connect scan tool MB991958 to the data link connector
(2) Turn the ignition switch to the "ON" position.
(3) Check if the DTC is set.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the check result satisfactory?

YES : The procedure is complete.
NO :  Return to Step 1.

AC609165

20

15

10

5

0

AB

10
(50)

30
(86)

RESISTANCE

(k

Ω)

TEMPERATURE ºC (ºF)

  0
(32)

  40
(104)

-10
(14)

 20
(68)

AUTO A/C DIAGNOSIS

TSB Revision

HEATER, AIR CONDITIONING AND VENTILATION

55-13

DTC B1000: Control Panel Communication Error

.

DTC SET CONDITION

DTC B1000 will be set when the communication between 
A/C-ECU and A/C control panel cannot be performed.

.

TECHNICAL DESCRIPTION (COMMENT)

Current trouble

• The A/C-ECU, the A/C control panel, or connector(s) or wir-

ing between the two may be defective.

A/C Control Panel Circuit

A/C-ECU

ETACS-ECU

A/C
CONTROL
PANEL

CPU

INTERFACE
CIRCUIT

POWER
SUPPLY

AC708596

AC708951AJ

Connectors: C-22, C-123

C-123

C-22 (B)

AC708972AB

Connector: C-317

Junction block

AUTO A/C DIAGNOSIS

TSB Revision

HEATER, AIR CONDITIONING AND VENTILATION

55-14

Past trouble

• If DTC B1000 is stored as a past trouble, carry out diagno-

sis with particular emphasis on wiring and connector(s) 
between the A/C-ECU and the A/C control panel. If the con-
nectors and wiring are normal, and obviously the ECU is the 
cause of the trouble, replace the ECU. If in doubt, do not 
replace the ECU.

.

TROUBLESHOOTING HINT

• Malfunction of connector.

• Malfunction of the harness.

• Malfunction of the A/C control panel.

• Malfunction of the A/C-ECU.

DIAGNOSIS

Required Special Tool:

•  MB991958: Scan Tool (M.U.T.-III Sub Assembly)

• MB991824: Vehicle Communication Interface (V.C.I.)

• MB991827: M.U.T.-III USB Cable

• MB991910: M.U.T.-III Main Harness A

STEP 1. Using scan tool MB991958, diagnose the CAN bus 
line.
Use scan tool MB991958 to diagnose the CAN bus lines.
(1) Connect scan tool MB991958 to the data link connector.
(2) Turn the ignition switch to "ON" position.
(3) Diagnose the CAN bus line.
Q: Is the check result satisfactory?

YES : Go to Step 2.
NO :  Repair the CAN bus lines. Repair the CAN bus lines 

(Refer to GROUP 54C, Diagnosis-Can Bus 
Diagnostic Chart 

P.54C-14

).

AC608435

Data link connector

MB991827

MB991824

MB991910

AB