Mitsubishi Evolution X. Manual — part 1268

AUTO A/C DIAGNOSIS

TSB Revision

HEATER, AIR CONDITIONING AND VENTILATION

55-23

STEP 3. Check A/C control panel connector C-123 and
A/C-ECU connector C-22 for loose, corroded or damaged
terminals, or terminals pushed back in the connector.
Q: Are A/C control panel connector C-123 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 9 and 10) and A/C control panel
connector C-123 (terminals 9 and 1).
Q: Is the wiring harness between A/C-ECU connector C-22

(terminal 9 and 10) and A/C control panel connector
C-123 (terminals 9 and 1) in good condition?
YES : Go to Step 5.
NO : Repair the wiring harness.

STEP 5. 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 DTC set?

YES : Replace the A/C control panel. Then go to Step 6.
NO : 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

.

STEP 6. 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 DTC set?

YES : Replace the A/C-ECU.
NO : 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

.

AUTO A/C DIAGNOSIS

TSB Revision

HEATER, AIR CONDITIONING AND VENTILATION

55-24

DTC B1021: Fan Dial SW Error

.

DTC SET CONDITION

DTC B1021 will be set when the A/C-ECU cannot receive the
signal of blower knob.

.

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.

Past trouble

• If DTC B1021 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.

.

A/C Control Panel Circuit

A/C-ECU

A/C
CONTROL
PANEL

CPU

INTERFACE
CIRCUIT

AC708601

AC708951AJ

Connectors: C-22, C-123

C-123

C-22 (B)

AUTO A/C DIAGNOSIS

TSB Revision

HEATER, AIR CONDITIONING AND VENTILATION

55-25

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

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. Refer to "How to connect the

Scan Tool (M.U.T.-III)

P.55-7

."

(2) Turn the ignition switch to the "ON" position.
(3) Diagnose the CAN bus line.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the CAN bus line found to be normal?

YES : Go to Step 2.
NO : Repair the CAN bus line. (Refer to GROUP 54C,

Diagnosis

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 DTC set?

YES : Go to Step 3.
NO : 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

.

AC608435

Data link connector

MB991827

MB991824

MB991910

AB

AUTO A/C DIAGNOSIS

TSB Revision

HEATER, AIR CONDITIONING AND VENTILATION

55-26

STEP 3. Check A/C control panel connector C-123 and
A/C-ECU connector C-22 for loose, corroded or damaged
terminals, or terminals pushed back in the connector.
Q: Are A/C control panel connector C-123 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 9 and 10) and A/C control panel
connector C-123 (terminals 9 and 1).
Q: Is the wiring harness between A/C-ECU connector C-22

(terminal 9 and 10) and A/C control panel connector
C-123 (terminals 9 and 1) in good condition?
YES : Go to Step 5.
NO : Repair the wiring harness.

STEP 5. 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 DTC set?

YES : Replace the A/C control panel. Then go to Step 6.
NO : 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

.

STEP 6. 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 DTC set?

YES : Replace the A/C-ECU.
NO : 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

.