AUTO A/C DIAGNOSIS
TSB Revision
HEATER, AIR CONDITIONING AND VENTILATION
55-19
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
.
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
.
AC608435
Data link connector
MB991827
MB991824
MB991910
AB