AUTO A/C DIAGNOSIS
TSB Revision
HEATER, AIR CONDITIONING AND VENTILATION
55-55
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 : There is an intermittent malfunction such as poor
engaged connector(s) or open circuit (Refer to
GROUP 00, How to Use Troubleshooting/Inspection
Service Points
− How to Cope with Intermittent
Malfunctions
P.00-15
.)
DTC U0155: Combination meter Time-out
CAUTION
If DTC U0155 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 air conditioning con-
trol-related signals from the combination meter via
the CAN bus lines. If any of the air conditioning con-
trol-related signals from the combination meter can-
not be received, the diagnostic trouble code U0155 is
stored.
.
TECHNICAL DESCRIPTION (COMMENT)
Current trouble
• Connector(s) or wiring harness in the CAN bus
lines between the combination meter and the
A/C-ECU, the power supply system to the combi-
nation meter, the combination meter itself, or the
A/C-ECU may be defective.
Past trouble
• If DTC U0155 is stored as a past trouble, carry
out diagnosis with particular emphasis on wiring
and connector(s) in the CAN bus line between
the A/C-ECU and the combination meter, and the
power supply system to the combination meter. If
the connectors and wiring are normal, and obvi-
ously the ECU is the cause of the trouble, replace
the ECU. If in doubt, do not replace the ECU.
NOTE: For a past trouble, you cannot find it by
the scan tool CAN bus diagnostics even if there is
a failure in CAN bus lines. In this case, refer to
GROUP 00, How to Use Troubleshooting/Inspec-
tion Service Points
−
How to Cope with Intermit-
tent Malfunctions
P.00-15
) and check the CAN
bus lines. You can narrow down the possible
cause of the trouble by referring to the DTC,
which is set regarding the CAN communica-
tion-linked ECUs (Refer to GROUP 54C, Expla-
nation about the scan too CAN bus diagnostics
P.54C-9
).
.
TROUBLESHOOTING HINTS
• Malfunction of the combination meter
• Malfunction of the A/C-ECU
• Damaged harness wires and connectors