Mitsubishi Evolution X. Manual - part 1273

AUTO A/C DIAGNOSIS

TSB Revision

HEATER, AIR CONDITIONING AND VENTILATION

55-43

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

55-44

DTC U1415: Coding Not Completed

CAUTION

If DTC U1415 is set in the A/C-ECU, diagnose the 
CAN main bus line.

CAUTION

Whenever the ECU is replaced, ensure that the 
communication circuit is normal.

.

TROUBLE JUDGMENT

The A/C-ECU receives the vehicle information sig-
nals from the ETACS-ECU via the CAN bus lines. If 
incorrect global coding data is received or coding 
data cannot be received with the ignition switch 
turned ON when the coding confirmation is com-
pleted, diagnostic trouble code U1415 is stored.

.

TROUBLESHOOTING HINTS

• Malfunction of the ETACS-ECU

• Malfunction of the A/C-ECU

• Damaged harness wires and connectors

DIAGNOSIS

Required Special Tools:

• MB991223: Harness Set

• MB992006: Extra Fine Probe

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

• MB991824: 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

).

AC608435

Data link connector

MB991827

MB991824

MB991910

AB

AUTO A/C DIAGNOSIS

TSB Revision

HEATER, AIR CONDITIONING AND VENTILATION

55-45

STEP 2. Using scan tool MB991958 read the ETACS-ECU 
diagnostic trouble code.
Check whether an ETACS DTC.
(1) Turn the ignition switch to the "ON" position.
(2) Check for the DTC related to the ETACS-ECU.
(3) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the DTC set?

YES :  Diagnose the ETACS-ECU (Refer to GROUP 54A, 

Diagnostic Trouble Code 

P.54A-582

 ).

NO :   Go to Step 3.

STEP 3. Using scan tool MB991958, check for any 
diagnostic trouble code.
Check if a DTC, which relates to CAN communication-linked 
systems below, is set.

• WCM <vehicles with WCM>

B2204: Coding data unmatched

• KOS <vehicles with KOS>

B2204: Coding data unmatched

(1) Turn the ignition switch to the "ON" position.
(2) Check for a DTC related to the relevant system.
(3) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the DTC set?

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

STEP 4. Recheck for diagnostic trouble code.
Check again if the DTC is set.
(1) Turn the ignition switch to the "ON" position.
(2) Check if the DTC is set.
(3) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the DTC set?

YES :  Replace the ETACS-ECU. On completion, check that 

the DTC is not reset.

NO :  A poor connection, open circuit or other intermittent 

malfunction is present in the lines between the 
ETACS-ECU and the A/C-ECU (Refer to GROUP 
00E, Harness Connector Inspection 

P.00E-2

).

STEP 5. Recheck for diagnostic trouble code.
Check again if the DTC is set.
(1) Turn the ignition switch to the "ON" position.
(2) Check if the DTC is set.
(3) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the DTC set?

YES : Replace the A/C-ECU. On completion, check that the 

DTC is not reset.

NO :  A poor connection, open circuit or other intermittent 

malfunction is present in the lines between the 
ETACS-ECU and the A/C-ECU (Refer to GROUP 
00E, Harness Connector Inspection 

P.00E-2

).

AUTO A/C DIAGNOSIS

TSB Revision

HEATER, AIR CONDITIONING AND VENTILATION

55-46

DTC U0019: Bus Off (CAN1)

CAUTION

If DTC U0019is set in the A/C-ECU, diagnose the 
CAN main bus line.

CAUTION

Whenever the ECU is replaced, ensure that the 
communication circuit is normal.

.

TROUBLE JUDGMENT

DTC U0019 will be stored when the A/C-ECU ceases 
CAN communication (bus off) and then resumes the 
communication when the ignition switch is turned to 
the "LOCK" (OFF) position.

.

TECHNICAL DESCRIPTION (COMMENT) 

The wiring harness wire or connectors may have 
loose, corroded, or damage terminals, or terminals 
pushed back in the connector, or the A/C-ECU may 
be defective.

.

TROUBLESHOOTING HINTS

• Defective connector(s) or wiring harness

• Malfunction of the A/C-ECU

DIAGNOSIS

Required Special Tools:

• MB991223: Harness Set

• MB992006: Extra Fine Probe

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

• MB991824: 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

).

AC608435

Data link connector

MB991827

MB991824

MB991910

AB